Measurements of the absolute branching fractions for D-Kbar pi e+ nu_e, D- Kbar e+nu_e and

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中心实验室英文常见术语

中心实验室英文常见术语In the heart of the scientific community, the central laboratory stands as a hub of innovation and discovery. Here, a lexicon of terms is as essential as the tools of the trade."Experiment" is a cornerstone term, referring to a testor investigation to discover something or test a hypothesis.It's where curiosity meets methodology."Hypothesis" is the starting point of any scientific inquiry, a proposed explanation that can be tested by observation and experimentation."Data" is the raw material of research, collected through observation and measurement, and is the basis for analysisand conclusions."Variable" is a crucial concept, referring to any factor, trait, or condition that can change and potentially affectthe outcome of an experiment."Control" is a fundamental element in experimental design, where a standard is maintained to compare the effects of the experimental manipulation."Observation" is the act of watching and recording phenomena, a key step in gathering data without influencingthe outcome."Replication" ensures the reliability of findings, where an experiment is repeated under the same conditions to confirm results."Peer review" is a critical process in the scientific community, where research is evaluated by other experts to maintain standards and integrity."Publication" is the culmination of research efforts, where findings are shared with the scientific community through journals and conferences.。

2017年赵忠尧博士后答辩-IndicoIHEP

首先重建的反冲侧，再通过拟合 (∗) 丢失不变质量谱来估计两种过程的产额。
Page . 6
工作经历与成绩，BESIII物理分析
主导 Measurements of the EM Form Factor of ，[memo准备中].
深刻理解核子结构测量核子形状因子检验近阈条件下的理论预言 preliminary
初步结论： 1. 完成了纯中性过程的TOF重建，也是对 BES3离线重建的完善。 2. 研究了纯中性过程的事例起始时间的计算方法。 3. 研究了中子/反中子/光子的鉴别方法。 4. 使用TOF双标记方法寻找信号过程，并取得了初步的结果。
拟合中子飞行时间的测量值与预期值之差来估计观测截面@ =2.0 GeV XS = 0.385 +- 0.076 (nb)
(1)
端盖量能器击中频率分布
(2)
(3)
(4)
(4)
Pileup效应的模拟
FPGA读出的模拟
Digi时间戳的还原根据时空分布重建簇射
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工作经历与成绩，PANDA探测器模拟与优化
主导基于时间戳的缪子探测器(Mini Drift Tube, MDT)模拟与重建系统
1. 2. 3. 4. 5. 6. 基于硬件配置使用Garfield模拟一组MDT的响应建立参数化的MDT响应模型，比如感应电流的波形把波形分析后的数字信号送入基于时间戳的模拟系统把仿真DAQ中的流水线数字信号进行径迹重建再把MDT打包的径迹段送给全局寻迹算法再基于重建的mu子研究DRELL-YAN过程
2017年赵忠尧博士后答辩
胡继峰
Page . 2
简历
▪ 2016-至今, 上海交通大学，博士后 ▪ 2014-2016, 都灵大学，博士后 ▪ 2011-2014, 吉森大学，博士后 ▪ 2007-2011, 国科大，博士 ▪ 2004-2007, 中科大(高能所联合培养)，硕士 ▪ 2000-2004, 郑州大学，学士

化学专业英语电子版

Chapter 1 Matter and MeasurementChemistry is the science of matter and the changes it undergoes. Chemists study the composition, structure, and properties of matter. They observe the changes that matter undergoes and measure the energy that is produced or consumed during these changes. Chemistry provides an understanding of many natural events and has led to the synthesis of new forms of matter that have greatly affected the way we live.Disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, organic chemistry, physical chemistry, analytical chemistry, polymer chemistry, biochemistry, and many more specialized disciplines, e.g. radiochemistry, theoretical chemistry.Chemistry is often called "the central science" because it connects the other natural sciences such as astronomy, physics, material science, biology and geology.1.1. Classification of MatterMatter is usually defined as anything that has mass and occupies space. Mass is the amount of matter in an object. The mass of an object does not change. The volume of an object is how much space the object takes up.All the different forms of matter in our world fall into two principal categories: (1) pure substances and (2) mixtures. A pure substance can also be defined as a form of matter that has both definite composition and distinct properties. Pure substances are subdivided into two groups: elements and compounds. An element is the simplest kind of material with unique physical and chemical properties; it can not be broken down into anything simpler by either physical or chemical means. A compound is a pure substance that consists of two or more elements linked together in characteristic and definite proportions; it can be decomposed by a chemical change into simpler substances with a fixedmass ratio. Mixtures contain two or more chemical substances in variable proportions in which the pure substances retain their chemical identities. In principle, they can be separated into the component substances by physical means, involving physical changes. A sample is homogeneous if it always has the same composition, no matter what part of the sample is examined. Pure elements and pure chemical compounds are homogeneous. Mixtures can be homogeneous, too; in a homogeneous mixture the constituents are distributed uniformly and the composition and appearance of the mixture are uniform throughout. A solutions is a special type of homogeneous mixture. A heterogeneous mixture has physically distinct parts with different properties. The classification of matter is summarized in the diagram below:Matter can also be categorized into four distinct phases: solid, liquid, gas, and plasma. The solid phase of matter has the atoms packed closely together. An object that is solid has a definite shape and volume that cannot be changed easily. The liquid phase of matter has the atoms packed closely together, but they flow freely around each other. Matter that is liquid has a definite volume but changes shape quite easily. Solids and liquids are termed condensed phases because of their well-defined volumes. The gas phase of matter has the atoms loosely arranged so they can travel in and out easily. A gas has neither specific shape nor constant volume. The plasma phase of matter has the atoms existing in an excited state.1.2. Properties of MatterAll substances have properties, the characteristics that give each substance its unique identity. We learn about matter by observing its properties. To identify a substance, chemists observe two distinct types of properties, physical and chemical, which are closely related to two types of change that matter undergoes.Physical properties are those that a substance shows by itself, without changing into or interacting with another substance. Some physical properties are color, smell, temperature, boiling point, electrical conductivity, and density. A physical change is a change that does not alter the chemical identity of the matter. A physical change results in different physical properties. For example, when ice melts, several physical properties have changed, such as hardness, density, and ability to flow. But the sample has not changed its composition: it is still water.Chemical properties are those that do change the chemical nature of matter. A chemical change, also called a chemical reaction, is a change that does alter the chemical identity of the substance. It occurs when a substance (or substances) is converted into a different substance (or substances). For example, when hydrogen burns in air, it undergoes a chemical change because it combines with oxygen to form water.Separation of MixturesThe separation of mixtures into its constituents in a pure state is an important process in chemistry. The constituents of any mixture can be separated on the basis of their differences in their physical and chemical properties, e.g., particle size, solubility, effect of heat, acidity or basicity etc.Some of the methods for separation of mixtures are:(1)Sedimentation or decantation. To separatethe mixture of coarse particles of a solidfrom a liquid e.g., muddy river water.(2)Filtration. To separate the insoluble solidcomponent of a mixture from the liquidcompletely i.e. separating the precipitate(solid phase) from any solution.(3)Evaporation. To separate a non-volatilesoluble salt from a liquid or recover thesoluble solid solute from the solution.(4)Crystallization. To separate a solidcompound in pure and geometrical form.(5)Sublimation. To separate volatile solids,from a non-volatile solid.(6)Distillation. To separate the constituents of aliquid mixture, which differ in their boilingpoints.(7)Solvent extraction method. Organiccompounds, which are easily soluble inorganic solvents but insoluble or immisciblewith water forming two separate layers canbe easily separated.1.3 Atoms, Molecules and CompoundsThe fundamental unit of a chemical substance is called an atom. The word is derived from the Greek atomos, meaning “undivisible”or “uncuttable”.An atom is the smallest possible particle of a substance.Molecule is the smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms;a group of like or different atoms held together by chemical forces. A molecule may consist of atoms of a single chemical element, as with oxygen (O2), or of different elements, as with water (H2O).A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons. Until March 2010, 118 elements have been observed. 94 elements occur naturally on earth, either as the pure element or more commonly as a component in compounds. 80 elements have stable isotopes, namely all elements with atomic numbers 1 to 82, except elements 43 and 61 (technetium and promethium). Elements with atomic numbers 83 or higher (bismuth and above) are inherently unstable, and undergo radioactive decay. The elements from atomic number 83 to 94 have no stable nuclei, but are nevertheless found in nature, either surviving as remnants of the primordial stellar nucleosynthesisthat produced the elements in the solar system, or else produced as short-lived daughter-isotopes through the natural decay of uranium and thorium. The remaining 24 elements so are artificial, or synthetic, elements, which are products of man-induced processes. These synthetic elements are all characteristically unstable. Although they have not been found in nature, it is conceivable that in the early history of the earth, these and possibly other unknown elements may have been present. Their unstable nature could have resulted in their disappearance from the natural components of the earth, however.The naturally occurring elements were not all discovered at the same time. Some, such as gold, silver, iron, lead, and copper, have been known since the days of earliest civilizations. Others, such as helium, radium, aluminium, and bromine, were discovered in the nineteenth century. The most abundant elements found in the earth’s crust, in order of decreasing percentage, are oxygen, silicon, aluminium, and iron. Others present in amounts of 1% or more are calcium, sodium, potassium, and magnesium. Together, these represent about 98.5% of the earth’s crust.The nomenclature and their origins of all known elements will be described in Chapter 2.A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together in a defined spatial arrangement by chemical bonds. Compounds that exist as molecules are called molecular compounds. An ionic compound is a chemical compound in which ions are held together in a lattice structure by ionic bonds. Usually, the positively charged portion consists of metal cations and the negatively charged portion is an anion or polyatomic ion.The relative amounts of the elements in a particular compound do not change: Every molecule of a particular chemical substance contains acharacteristic number of atoms of its constituent elements. For example, every water molecule contains two hydrogen atoms and one oxygen atom. To describe this atomic composition, chemists write the chemical formula for water as H2O.The chemical formula for water shows how formulas are constructed. The formula lists the symbols of all elements found in the compound, in this case H (hydrogen) and O (oxygen). A subscript number after an element's symbol denotes how many atoms of that element are present in the molecule. The subscript 2 in the formula for water indicates that each molecule contains two hydrogen atoms. No subscript is used when only one atom is present, as is the case for the oxygen atom in a water molecule. Atoms are indivisible, so molecules always contain whole numbers of atoms. Consequently, the subscripts in chemical formulas of molecular substances are always integers. We explore chemical formulas in greater detail in Chapter 2.The simple formula that gives the simplest whole number ratio between the atoms of the various elements present in the compound is called its empirical formula. The simplest formula that gives the actual number of atoms of the various elements present in a molecule of any compound is called its molecular formula. Elemental analysis is an experiment that determines the amount (typically a weight percent) of an element in a compound. The elemental analysis permits determination of the empirical formula, and the molecular weight and elemental analysis permit determination of the molecular formula.1.4. Numbers in Physical Quantities1.4.1. Measurement1.Physical QuantitiesPhysical properties such as height, volume, and temperature that can be measured are called physical quantity. A number and a unit of defined size are required to describe physical quantity, for example, 10 meters, 9 kilograms.2.Exact NumbersExact Numbers are numbers known withcertainty. They have unlimited number of significant figures. They arise by directly counting numbers, for example, the number of sides on a square, or by definition:1 m = 100 cm, 1 kg = 1000 g1 L = 1000 mL, 1 minute = 60seconds3.Uncertainty in MeasurementNumbers that result from measurements are never exact. Every experimental measurement, no matter how precise, has a degree of uncertainty to it because there is a limit to the number of digits that can be determined. There is always some degree of uncertainty due to experimental errors: limitations of the measuring instrument, variations in how each individual makes measurements, or other conditions of the experiment.Precision and AccuracyIn the fields of engineering, industry and statistics, the accuracy of a measurement system is the degree of closeness of measurements results to its actual (true) value. The precision of a measurement system, also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results. Although the two words can be synonymous in colloquial use, they are deliberately contrasted in the context of the scientific method.A measurement system can be accurate but not precise, precise but not accurate, neither, or both. A measurement system is called valid if it is both accurate and precise. Related terms are bias (non-random or directed effects caused by a factor or factors unrelated by the independent variable) and error(random variability), respectively. Random errors result from uncontrolled variables in an experiment and affect precision; systematic errors can be assigned to definite causes and affect accuracy. For example, if an experiment contains a systematic error, then increasing the sample size generally increases precision but does not improve accuracy. Eliminating the systematic error improves accuracy but does not change precision.1.4.2 Significant FiguresThe number of digits reported in a measurement reflects the accuracy of the measurement and the precision of the measuring device. Significant figures in a number include all of the digits that are known with certainty, plus the first digit to the right that has an uncertain value. For example, the uncertainty in the mass of a powder sample, i.e., 3.1267g as read from an “analytical balance” is 0.0001g.In any calculation, the results are reported to the fewest significant figures (for multiplication and division) or fewest decimal places (addition and subtraction).1.Rules for deciding the number of significantfigures in a measured quantity:The number of significant figures is found by counting from left to right, beginning with the first nonzero digit and ending with the digit that has the uncertain value, e.g.,459 (3) 0.206 (3) 2.17(3) 0.00693 (3) 25.6 (3) 7390 (3) 7390. (4)(1)All nonzero digits are significant, e.g., 1.234g has 4 significant figures, 1.2 g has 2significant figures.(2)Zeroes between nonzero digits aresignificant: e.g., 1002 kg has 4 significantfigures, 3.07 mL has 3 significant figures.(3)Leading zeros to the left of the first nonzerodigits are not significant; such zeroes merelyindicate the position of the decimal point:e.g., 0.001 m has only 1 significant figure,0.012 g has 2 significant figures.(4)Trailing zeroes that are also to the right of adecimal point in a number are significant:e.g., 0.0230 mL has 3 significant figures,0.20 g has 2 significant figures.(5)When a number ends in zeroes that are notto the right of a decimal point, the zeroes arenot necessarily significant: e.g., 190 milesmay be 2 or 3 significant figures, 50,600calories may be 3, 4, or 5 significant figures.The potential ambiguity in the last rule can be avoided by the use of standard exponential, or "scientific" notation. For example, depending onwhether the number of significant figures is 3, 4, or 5, we would write 50,600 calories as:5.06 × 104 calories (3 significant figures)5.060 ×104calories (4 significant figures), or5.0600 × 104 calories (5 significant figures).2.Rules for rounding off numbers(1)If the digit to be dropped is greater than 5,the last retained digit is increased by one.For example, 12.6 is rounded to 13.(2)If the digit to be dropped is less than 5, thelast remaining digit is left as it is. Forexample, 12.4 is rounded to 12.(3)If the digit to be dropped is 5, and if anydigit following it is not zero, the lastremaining digit is increased by one. Forexample, 12.51 is rounded to 13.(4)If the digit to be dropped is 5 and isfollowed only by zeroes, the last remainingdigit is increased by one if it is odd, but leftas it is if even. For example, 11.5 is roundedto 12, 12.5 is rounded to 12.This rule means that if the digit to be dropped is 5 followed only by zeroes, the result is always rounded to the even digit. The rationale is to avoid bias in rounding: half of the time we round up, half the time we round down.3.Arithmetic using significant figuresIn carrying out calculations, the general rule is that the accuracy of a calculated result is limited by the least accurate measurement involved in the calculation.(1) In addition and subtraction, the result is rounded off to the last common digit occurring furthest to the right in all components. Another way to state this rules, is that, in addition and subtraction, the result is rounded off so that it has the same number of decimal places as the measurement having the fewest decimal places. For example,100 (assume 3 significant figures) + 23.643 (5 significant figures) = 123.643,which should be rounded to 124 (3 significant figures).(2) In multiplication and division, the resultshould be rounded off so as to have the same number of significant figures as in the component with the least number of significant figures. For example,3.0 (2 significant figures ) ×12.60 (4 significant figures) = 37.8000which should be rounded off to 38 (2 significant figures).1.4.3 Scientific NotationScientific notation, also known as standard form or as exponential notation, is a way of writing numbers that accommodates values too large or small to be conveniently written in standard decimal notation.In scientific notation all numbers are written like this:a × 10b("a times ten to the power of b"), where the exponent b is an integer, and the coefficient a is any real number, called the significant or mantissa (though the term "mantissa" may cause confusion as it can also refer to the fractional part of the common logarithm). If the number is negative then a minus sign precedes a (as in ordinary decimal notation).In standard scientific notation the significant figures of a number are retained in a factor between 1 and 10 and the location of the decimal point is indicated by a power of 10. For example:An electron's mass is about 0.00000000000000000000000000000091093822 kg. In scientific notation, this is written 9.1093822×10−31 kg.The Earth's mass is about 5973600000000000000000000 kg. In scientific notation, this is written 5.9736×1024 kg.1.5 Units of Measurement1.5.1 Systems of Measurement1.United States Customary System (USCS)The United States customary system (also called American system) is the most commonly used system of measurement in the United States. It is similar but not identical to the British Imperial units. The U.S. is the only industrialized nation that does not mainly use the metric system in its commercial and standards activities. Base units are defined butseem arbitrary (e.g. there are 12 inches in 1 foot)2.MetricThe metric system is an international decimalized system of measurement, first adopted by France in 1791, that is the common system of measuring units used by most of the world. It exists in several variations, with different choices of fundamental units, though the choice of base units does not affect its day-to-day use. Over the last two centuries, different variants have been considered the metric system. Metric units are universally used in scientific work, and widely used around the world for personal and commercial purposes. A standard set of prefixes in powers of ten may be used to derive larger and smaller units from the base units.3.SISI system (for Système International) was adopted by the International Bureau of Weights and Measures in 1960, it is a revision and extension of the metric system. Scientists and engineers throughout the world in all disciplines are now being urged to use only the SI system of units.1.5.2 SI base unitsThe SI is founded on seven SI base units for seven base quantities assumed to be mutually independent, as given in Table 1.1.Table 1.1 SI Base Physical Quantities and UnitsU n i tN a m e UnitSymbolBaseQuantityQuantitySymbolDimensionSymbolm m l l Le t e r e n g t hk i lo g r a m kgmassm Ms ec o nd stimet Ta mp e r e AelectriccurrentI Ik el v i n KthermodynTΘm i ct e m p e r a t u r em o l e molamountofsubstancen Nc an d e l a cdluminousIvJntensity1.5.3 SI derived unitsOther quantities, called derived quantities, aredefined in terms of the seven base quantities via asystem of quantity equations. The SI derived unitsfor these derived quantities are obtained from theseequations and the seven SI base units. Examples ofsuch SI derived units are given in Table 1.2, where itshould be noted that the symbol 1 for quantities ofdimension 1 such as mass fraction is generallyomitted.Table 1.2 SI Derived Physical Quantities and(symbol) Unit(symbol)UArea (A) squaremeterm V olume (V) cubicmeterm Density (ρ) kilogramper cubicmeterkVelocity (u) meterpersecondmPressure (p) pascal(Pa)kEnergy (E) joule (J) (k Frequency (ν) hertz(Hz)1Quantity of electricity (Q) coulomb(C)AElectromotive force (E) volt (V) (kmsForce (F) newton(N)kFor ease of understanding and convenience, 22SI derived units have been given special names andsymbols, as shown in Table 1.3.Table 1.3 SI Derived Units with special names andsymbolsD e r i v e dq u a n t i t y SpecialnameSpecialSymbolExpressionintermsofotherSIunitsSIbaseunitsp r r ml a n ea n g l e adianad·m-1=1s o l i da n g l e steradiansrm2·m-2=1f r e q u e n c y hertzHzs-1f o r c e newtonN m·kg·s-2p p P N mr e s s u r e ,s t r e s s ascala/m21·kg·s-2e n e r g y ,w o r k ,q u a n t i t yo fh e a jouleJ N·mm2·kg·s-2p o w e r ,r a d i a n tf l u x wattW J/sm2·kg·s-3e l e c t r i cc h a r g e q u a n t i t y coulombC s·Afe l e c t r i c i t ye l e c t r i cp o t e n t i a l ,p o t e n t i a l voltV W/Am2·kg·s-3·A-1i f f e r e n c e ,e l e c t r o m o t i v ef o r c ec a p a c i t a n c e faradF C/Vm-2·kg-1·s 4·A 2e l e c t r i cr e s i s t a n c e ohmΩV/Am2·kg·s-3·A-2e l e c t r i cc o nd u c t a n c siemensS A/Vm-2·kg-1·s2·Aem a g n e t i cf l u x weberWbV·sm2·kg·s-2·A-1m a g n e t i cf l u xd e n s i t y teslaT Wb/m2kg·s-2·A-1i n d henH Wb/m2u c t a n c e ryA ·kg·s-2·A-2C e l s i u st e m p e r a t u r e degreeCelsius°CKl u m i n o u s lumenlmcd·srcd·srl u xi l l u m i n a n c e luxlxlm/m2m-2·cd·sra c t i v i t y( o far a d i o n u c l i d e becquerelBqs-1a b s o r b e dd o se ,s p e c i f i ce n e r g y( i m p a r t e d ) ,grayGyJ/kgm2·s-2e r m ad o s ee q u i v a l e n t ,e ta l .sievertSvJ/kgm2·s-2c a t a l y t i ca c t i v i katalkats-1·molyCertain units that are not part of the SI are essential and used so widely that they are accepted by the CIPM (Commission Internationale des Poids Et Mesures) for use with the SI. Some commonly used units are given in Table 1.4.Table 1.4 Non-SI units accepted for use with theSIN a m e SymbolQuantityEquivalentSIunitmi n u t e mintime1min=6sho u r htime1h6min=36s da y dtime1d=24h=144min=864sdegreeo fa r c °planeangle1°=(π/18)radm i n u t eo fa r c ′planeangle1′=(1/6)°=(π/18radsecondo fa r c ″planeangle1″=(1/6)′=(1/36)°=(π/648)rdhect a r e haarea1ha=1a=1m²l i t r e lorLvolume1l=1dm3=.1m3ton n e tmass1t=13kg=1MgThe 20 SI prefixes used to form decimal multiples and submultiples of SI units are given in Table 1.5.Table 1.5 SI PrefixesF a c t o r NameSymbolFactorNameSymbol1 0 24yottaY 1-1decid1 0 21zettZ 1-2centc。

Measurement of the Branching Fractions and CP Asymmetries of B--D0(cp)K- Decays with the Ba

a r X i v :h e p -e x /0408082v 1 17 A u g 2004B A B A R -CONF-04/039SLAC-PUB-10655Measurement of the Branching Fractions and CP Asymmetries of B −→D 0(CP )K −Decays with the B A B A R Detector The B A B A R Collaboration February 7,2008Abstract We present a study of B −→D 0(CP )K −decays,where D 0(CP )is reconstructed in ﬂavor (K −π+),CP -even (K −K +,π−π+)and CP -odd (K 0S π0)eigenstates,based on a sample of about 214million Υ(4S )→BB (B −→D 0K −)/B (B −→D 0π−)=0.87±0.14(stat)±0.06(syst),R −≡B (B −→D 0CP −K −)/B (B −→D 0CP −π−)B (B −→D 0CP +K −)+B (B +→D 0CP +K +)=0.40±0.15(stat)±0.08(syst)B(B−→D0CP−K−)−B(B+→D0CP−K+)A CP−≡Work supported in part by Department of Energy contract DE-AC03-76SF00515.The B A B A R Collaboration,B.Aubert,R.Barate,D.Boutigny,F.Couderc,J.-M.Gaillard,A.Hicheur,Y.Karyotakis,J.P.Lees,V.Tisserand,A.ZghicheLaboratoire de Physique des Particules,F-74941Annecy-le-Vieux,FranceA.Palano,A.PompiliUniversit`a di Bari,Dipartimento di Fisica and INFN,I-70126Bari,ItalyJ.C.Chen,N.D.Qi,G.Rong,P.Wang,Y.S.ZhuInstitute of High Energy Physics,Beijing100039,ChinaG.Eigen,I.Ofte,B.StuguUniversity of Bergen,Inst.of Physics,N-5007Bergen,NorwayG.S.Abrams,A.W.Borgland,A.B.Breon,D.N.Brown,J.Button-Shafer,R.N.Cahn,E.Charles, C.T.Day,M.S.Gill,A.V.Gritsan,Y.Groysman,R.G.Jacobsen,R.W.Kadel,J.Kadyk,L.T.Kerth,Yu.G.Kolomensky,G.Kukartsev,G.Lynch,L.M.Mir,P.J.Oddone,T.J.Orimoto,M.Pripstein,N.A.Roe,M.T.Ronan,V.G.Shelkov,W.A.WenzelLawrence Berkeley National Laboratory and University of California,Berkeley,CA94720,USAM.Barrett,K.E.Ford,T.J.Harrison,A.J.Hart,C.M.Hawkes,S.E.Morgan,A.T.Watson University of Birmingham,Birmingham,B152TT,United KingdomM.Fritsch,K.Goetzen,T.Held,H.Koch,B.Lewandowski,M.Pelizaeus,M.SteinkeRuhr Universit¨a t Bochum,Institut f¨u r Experimentalphysik1,D-44780Bochum,GermanyJ.T.Boyd,N.Chevalier,W.N.Cottingham,M.P.Kelly,tham,F.F.WilsonUniversity of Bristol,Bristol BS81TL,United KingdomT.Cuhadar-Donszelmann,C.Hearty,N.S.Knecht,T.S.Mattison,J.A.McKenna,D.Thiessen University of British Columbia,Vancouver,BC,Canada V6T1Z1A.Khan,P.Kyberd,L.TeodorescuBrunel University,Uxbridge,Middlesex UB83PH,United KingdomA.E.Blinov,V.E.Blinov,V.P.Druzhinin,V.B.Golubev,V.N.Ivanchenko,E.A.Kravchenko,A.P.Onuchin,S.I.Serednyakov,Yu.I.Skovpen,E.P.Solodov,A.N.YushkovBudker Institute of Nuclear Physics,Novosibirsk630090,RussiaD.Best,M.Bruinsma,M.Chao,I.Eschrich,D.Kirkby,nkford,M.Mandelkern,R.K.Mommsen,W.Roethel,D.P.StokerUniversity of California at Irvine,Irvine,CA92697,USAC.Buchanan,B.L.HartﬁelUniversity of California at Los Angeles,Los Angeles,CA90024,USAS.D.Foulkes,J.W.Gary,B.C.Shen,K.WangUniversity of California at Riverside,Riverside,CA92521,USAD.del Re,H.K.Hadavand,E.J.Hill,D.B.MacFarlane,H.P.Paar,Sh.Rahatlou,V.SharmaUniversity of California at San Diego,La Jolla,CA92093,USAJ.W.Berryhill,C.Campagnari,B.Dahmes,O.Long,A.Lu,M.A.Mazur,J.D.Richman,W.Verkerke University of California at Santa Barbara,Santa Barbara,CA93106,USAT.W.Beck,A.M.Eisner,C.A.Heusch,J.Kroseberg,W.S.Lockman,G.Nesom,T.Schalk,B.A.Schumm,A.Seiden,P.Spradlin,D.C.Williams,M.G.WilsonUniversity of California at Santa Cruz,Institute for Particle Physics,Santa Cruz,CA95064,USAJ.Albert,E.Chen,G.P.Dubois-Felsmann,A.Dvoretskii,D.G.Hitlin,I.Narsky,T.Piatenko,F.C.Porter,A.Ryd,A.Samuel,S.YangCalifornia Institute of Technology,Pasadena,CA91125,USAS.Jayatilleke,G.Mancinelli,B.T.Meadows,M.D.SokoloﬀUniversity of Cincinnati,Cincinnati,OH45221,USAT.Abe,F.Blanc,P.Bloom,S.Chen,W.T.Ford,U.Nauenberg,A.Olivas,P.Rankin,J.G.Smith,J.Zhang,L.ZhangUniversity of Colorado,Boulder,CO80309,USAA.Chen,J.L.Harton,A.Soﬀer,W.H.Toki,R.J.Wilson,Q.ZengColorado State University,Fort Collins,CO80523,USAD.Altenburg,T.Brandt,J.Brose,M.Dickopp,E.Feltresi,A.Hauke,cker,R.M¨u ller-Pfeﬀerkorn, R.Nogowski,S.Otto,A.Petzold,J.Schubert,K.R.Schubert,R.Schwierz,B.Spaan,J.E.Sundermann Technische Universit¨a t Dresden,Institut f¨u r Kern-und Teilchenphysik,D-01062Dresden,GermanyD.Bernard,G.R.Bonneaud,F.Brochard,P.Grenier,S.Schrenk,Ch.Thiebaux,G.Vasileiadis,M.VerderiEcole Polytechnique,LLR,F-91128Palaiseau,FranceD.J.Bard,P.J.Clark,vin,F.Muheim,S.Playfer,Y.XieUniversity of Edinburgh,Edinburgh EH93JZ,United KingdomM.Andreotti,V.Azzolini,D.Bettoni,C.Bozzi,R.Calabrese,G.Cibinetto,E.Luppi,M.Negrini,L.Piemontese,A.SartiUniversit`a di Ferrara,Dipartimento di Fisica and INFN,I-44100Ferrara,ItalyE.TreadwellFlorida A&M University,Tallahassee,FL32307,USAF.Anulli,R.Baldini-Ferroli,A.Calcaterra,R.de Sangro,G.Finocchiaro,P.Patteri,I.M.Peruzzi,M.Piccolo,A.ZalloLaboratori Nazionali di Frascati dell’INFN,I-00044Frascati,ItalyA.Buzzo,R.Capra,R.Contri,G.Crosetti,M.Lo Vetere,M.Macri,M.R.Monge,S.Passaggio,C.Patrignani,E.Robutti,A.Santroni,S.TosiUniversit`a di Genova,Dipartimento di Fisica and INFN,I-16146Genova,ItalyS.Bailey,G.Brandenburg,K.S.Chaisanguanthum,M.Morii,E.WonHarvard University,Cambridge,MA02138,USAR.S.Dubitzky,ngeneggerUniversit¨a t Heidelberg,Physikalisches Institut,Philosophenweg12,D-69120Heidelberg,Germany W.Bhimji,D.A.Bowerman,P.D.Dauncey,U.Egede,J.R.Gaillard,G.W.Morton,J.A.Nash,M.B.Nikolich,G.P.TaylorImperial College London,London,SW72AZ,United KingdomM.J.Charles,G.J.Grenier,U.MallikUniversity of Iowa,Iowa City,IA52242,USAJ.Cochran,H.B.Crawley,msa,W.T.Meyer,S.Prell,E.I.Rosenberg,A.E.Rubin,J.YiIowa State University,Ames,IA50011-3160,USAM.Biasini,R.Covarelli,M.PioppiUniversit`a di Perugia,Dipartimento di Fisica and INFN,I-06100Perugia,ItalyM.Davier,X.Giroux,G.Grosdidier,A.H¨o cker,place,F.Le Diberder,V.Lepeltier,A.M.Lutz, T.C.Petersen,S.Plaszczynski,M.H.Schune,L.Tantot,G.WormserLaboratoire de l’Acc´e l´e rateur Lin´e aire,F-91898Orsay,FranceC.H.Cheng,nge,M.C.Simani,D.M.WrightLawrence Livermore National Laboratory,Livermore,CA94550,USAA.J.Bevan,C.A.Chavez,J.P.Coleman,I.J.Forster,J.R.Fry,E.Gabathuler,R.Gamet,D.E.Hutchcroft,R.J.Parry,D.J.Payne,R.J.Sloane,C.TouramanisUniversity of Liverpool,Liverpool L6972E,United KingdomJ.J.Back,1C.M.Cormack,P.F.Harrison,1F.Di Lodovico,G.B.Mohanty1Queen Mary,University of London,E14NS,United KingdomC.L.Brown,G.Cowan,R.L.Flack,H.U.Flaecher,M.G.Green,P.S.Jackson,T.R.McMahon,S.Ricciardi,F.Salvatore,M.A.WinterUniversity of London,Royal Holloway and Bedford New College,Egham,Surrey TW200EX,United KingdomD.Brown,C.L.DavisUniversity of Louisville,Louisville,KY40292,USAJ.Allison,N.R.Barlow,R.J.Barlow,P.A.Hart,M.C.Hodgkinson,ﬀerty,A.J.Lyon,J.C.WilliamsUniversity of Manchester,Manchester M139PL,United KingdomA.Farbin,W.D.Hulsbergen,A.Jawahery,D.Kovalskyi,e,V.Lillard,D.A.RobertsUniversity of Maryland,College Park,MD20742,USAG.Blaylock,C.Dallapiccola,K.T.Flood,S.S.Hertzbach,R.Koﬂer,V.B.Koptchev,T.B.Moore,S.Saremi,H.Staengle,S.WillocqUniversity of Massachusetts,Amherst,MA01003,USAR.Cowan,G.Sciolla,S.J.Sekula,F.Taylor,R.K.Yamamoto Massachusetts Institute of Technology,Laboratory for Nuclear Science,Cambridge,MA02139,USAD.J.J.Mangeol,P.M.Patel,S.H.RobertsonMcGill University,Montr´e al,QC,Canada H3A2T8zzaro,V.Lombardo,F.PalomboUniversit`a di Milano,Dipartimento di Fisica and INFN,I-20133Milano,ItalyJ.M.Bauer,L.Cremaldi,V.Eschenburg,R.Godang,R.Kroeger,J.Reidy,D.A.Sanders,D.J.Summers,H.W.ZhaoUniversity of Mississippi,University,MS38677,USAS.Brunet,D.Cˆo t´e,P.TarasUniversit´e de Montr´e al,Laboratoire Ren´e J.A.L´e vesque,Montr´e al,QC,Canada H3C3J7H.NicholsonMount Holyoke College,South Hadley,MA01075,USAN.Cavallo,2F.Fabozzi,2C.Gatto,L.Lista,D.Monorchio,P.Paolucci,D.Piccolo,C.Sciacca Universit`a di Napoli Federico II,Dipartimento di Scienze Fisiche and INFN,I-80126,Napoli,ItalyM.Baak,H.Bulten,G.Raven,H.L.Snoek,L.WildenNIKHEF,National Institute for Nuclear Physics and High Energy Physics,NL-1009DB Amsterdam,The NetherlandsC.P.Jessop,J.M.LoSeccoUniversity of Notre Dame,Notre Dame,IN46556,USAT.Allmendinger,K.K.Gan,K.Honscheid,D.Hufnagel,H.Kagan,R.Kass,T.Pulliam,A.M.Rahimi,R.Ter-Antonyan,Q.K.WongOhio State University,Columbus,OH43210,USAJ.Brau,R.Frey,O.Igonkina,C.T.Potter,N.B.Sinev,D.Strom,E.TorrenceUniversity of Oregon,Eugene,OR97403,USAF.Colecchia,A.Dorigo,F.Galeazzi,M.Margoni,M.Morandin,M.Posocco,M.Rotondo,F.Simonetto,R.Stroili,G.Tiozzo,C.VociUniversit`a di Padova,Dipartimento di Fisica and INFN,I-35131Padova,ItalyM.Benayoun,H.Briand,J.Chauveau,P.David,Ch.de la Vaissi`e re,L.Del Buono,O.Hamon,M.J.J.John,Ph.Leruste,J.Malcles,J.Ocariz,M.Pivk,L.Roos,S.T’Jampens,G.Therin Universit´e s Paris VI et VII,Laboratoire de Physique Nucl´e aire et de Hautes Energies,F-75252Paris,FranceP.F.Manfredi,V.ReUniversit`a di Pavia,Dipartimento di Elettronica and INFN,I-27100Pavia,ItalyP.K.Behera,L.Gladney,Q.H.Guo,J.PanettaUniversity of Pennsylvania,Philadelphia,PA19104,USAC.Angelini,G.Batignani,S.Bettarini,M.Bondioli,F.Bucci,G.Calderini,M.Carpinelli,F.Forti, M.A.Giorgi,A.Lusiani,G.Marchiori,F.Martinez-Vidal,3M.Morganti,N.Neri,E.Paoloni,M.Rama,G.Rizzo,F.Sandrelli,J.WalshUniversit`a di Pisa,Dipartimento di Fisica,Scuola Normale Superiore and INFN,I-56127Pisa,ItalyM.Haire,D.Judd,K.Paick,D.E.WagonerPrairie View A&M University,Prairie View,TX77446,USAN.Danielson,P.Elmer,u,C.Lu,V.Miftakov,J.Olsen,A.J.S.Smith,A.V.TelnovPrinceton University,Princeton,NJ08544,USAF.Bellini,G.Cavoto,4R.Faccini,F.Ferrarotto,F.Ferroni,M.Gaspero,L.Li Gioi,M.A.Mazzoni,S.Morganti,M.Pierini,G.Piredda,F.Safai Tehrani,C.VoenaUniversit`a di Roma La Sapienza,Dipartimento di Fisica and INFN,I-00185Roma,ItalyS.Christ,G.Wagner,R.WaldiUniversit¨a t Rostock,D-18051Rostock,GermanyT.Adye,N.De Groot,B.Franek,N.I.Geddes,G.P.Gopal,E.O.Olaiya Rutherford Appleton Laboratory,Chilton,Didcot,Oxon,OX110QX,United KingdomR.Aleksan,S.Emery,A.Gaidot,S.F.Ganzhur,P.-F.Giraud,G.Hamel de Monchenault,W.Kozanecki, M.Legendre,G.W.London,B.Mayer,G.Schott,G.Vasseur,Ch.Y`e che,M.ZitoDSM/Dapnia,CEA/Saclay,F-91191Gif-sur-Yvette,FranceM.V.Purohit,A.W.Weidemann,J.R.Wilson,F.X.YumicevaUniversity of South Carolina,Columbia,SC29208,USAD.Aston,R.Bartoldus,N.Berger,A.M.Boyarski,O.L.Buchmueller,R.Claus,M.R.Convery,M.Cristinziani,G.De Nardo,D.Dong,J.Dorfan,D.Dujmic,W.Dunwoodie,E.E.Elsen,S.Fan, R.C.Field,T.Glanzman,S.J.Gowdy,T.Hadig,V.Halyo,C.Hast,T.Hryn’ova,W.R.Innes, M.H.Kelsey,P.Kim,M.L.Kocian,D.W.G.S.Leith,J.Libby,S.Luitz,V.Luth,H.L.Lynch,H.Marsiske,R.Messner,D.R.Muller,C.P.O’Grady,V.E.Ozcan,A.Perazzo,M.Perl,S.Petrak, B.N.Ratcliﬀ,A.Roodman,A.A.Salnikov,R.H.Schindler,J.Schwiening,G.Simi,A.Snyder,A.Soha,J.Stelzer,D.Su,M.K.Sullivan,J.Va’vra,S.R.Wagner,M.Weaver,A.J.R.Weinstein, W.J.Wisniewski,M.Wittgen,D.H.Wright,A.K.Yarritu,C.C.YoungStanford Linear Accelerator Center,Stanford,CA94309,USAP.R.Burchat,A.J.Edwards,T.I.Meyer,B.A.Petersen,C.RoatStanford University,Stanford,CA94305-4060,USAS.Ahmed,M.S.Alam,J.A.Ernst,M.A.Saeed,M.Saleem,F.R.WapplerState University of New York,Albany,NY12222,USAW.Bugg,M.Krishnamurthy,S.M.SpanierUniversity of Tennessee,Knoxville,TN37996,USAR.Eckmann,H.Kim,J.L.Ritchie,A.Satpathy,R.F.SchwittersUniversity of Texas at Austin,Austin,TX78712,USAJ.M.Izen,I.Kitayama,X.C.Lou,S.YeUniversity of Texas at Dallas,Richardson,TX75083,USAF.Bianchi,M.Bona,F.Gallo,D.GambaUniversit`a di Torino,Dipartimento di Fisica Sperimentale and INFN,I-10125Torino,ItalyL.Bosisio,C.Cartaro,F.Cossutti,G.Della Ricca,S.Dittongo,S.Grancagnolo,nceri,P.Poropat,5L.Vitale,G.VuagninUniversit`a di Trieste,Dipartimento di Fisica and INFN,I-34127Trieste,ItalyR.S.PanviniVanderbilt University,Nashville,TN37235,USASw.Banerjee,C.M.Brown,D.Fortin,P.D.Jackson,R.Kowalewski,J.M.Roney,R.J.SobieUniversity of Victoria,Victoria,BC,Canada V8W3P6H.R.Band,B.Cheng,S.Dasu,M.Datta,A.M.Eichenbaum,M.Graham,J.J.Hollar,J.R.Johnson,P.E.Kutter,H.Li,R.Liu,A.Mihalyi,A.K.Mohapatra,Y.Pan,R.Prepost,P.Tan,J.H.vonWimmersperg-Toeller,J.Wu,S.L.Wu,Z.YuUniversity of Wisconsin,Madison,WI53706,USAM.G.Greene,H.NealYale University,New Haven,CT06511,USA1INTRODUCTIONA theoretically clean measurement of the angleγ=arg(−V ud V∗ub/V cd V∗cb)can be obtained from the study of B−→D(∗)0K(∗)−decays by exploiting the interference between the b→c¯u s and b→u¯c s decay amplitudes[1].The method originally proposed by Gronau,Wyler and London is based on the interference between B−→D0K−and B−→D0decay to CP eigenstates.We deﬁne the ratios R and R CP±of Cabibbo-suppressed to Cabibbo-favored branching fractionsR(CP±)≡B(B−→D0(CP±)K−)+B(B+→B(B−→D0(CP±)π−)+B(B+→B(B−→D0CP±K−)+B(B+→D0CP±K+).(2)Neglecting the D0−D0π−)/A(B−→D0π−)of the amplitudes of the B−→D0K−)/A(B−→D0K−)|is the magnitude of the ratio of the amplitudes for the processes B−→B pairs collected with the B A B A R detector at the PEP-II asymmetric-energy B factory.The B A B A R detector is described in detail elsewhere[2].Charged-particle tracking is provided by aﬁve-layer silicon vertex tracker(SVT)and a40-layer drift chamber(DCH).For charged-particle identiﬁcation,ionization energy loss in the DCH and SVT,and Cherenkov radia-tion detected in a ring-imaging device(DIRC)are used.Photons are identiﬁed by the electromag-netic calorimeter(EMC),which comprises6580thallium-doped CsI crystals.These systems are mounted inside a1.5-T solenoidal superconducting magnet.The segmentedﬂux return,including endcaps,is instrumented with resistive plate chambers(IFR)for muon and K0Lidentiﬁcation.We use the GEANT[3]software to simulate interactions of particles traversing the detector,taking into account the varying accelerator and detector conditions.3ANALYSIS METHODWe reconstruct B−→D0h−decays,where the prompt track h−is a kaon or a pion.Reference to the charge-conjugate state is implied here and throughout the text unless otherwise stated.Candidates for D0are reconstructed in the CP-even eigenstatesπ−π+and K−K+,in the CP-odd eigenstate K0Sπ0,and in the non-CPﬂavor eigenstate K−π+.K0Scandidates are selected in theπ−π+channel.The prompt particle h−is required to have momentum greater than1.4GeV/c.Particle IDinformation from the drift chamber and,when available,from the DIRC must be consistent with the kaon hypothesis for the K meson candidate in all D0modes and with the pion hypothesis for theπ±meson candidates in the D0→π−π+mode.For the prompt track to be identiﬁed as a pion or a kaon,we require that at leastﬁve Cherenkov photons are detected to insure a good measurement of the Cherenkov angle.We reject a candidate track if its Cherenkov angle is not within3σof the expected value for either the kaon or pion mass hypothesis.We also reject candidate tracks that are identiﬁed as electrons by the DCH and the EMC or as muons by the DCH and the IFR.Photon candidates are clusters in the EMC that are not matched to any charged track,have a raw energy greater than30MeV and lateral shower shape consistent with the expected pattern of energy deposit from an electromagnetic shower.Photon pairs with invariant mass within the range 115–150MeV/c2(∼3σ)and total energy greater than200MeV are consideredπ0candidates. To improve the momentum resolution,theπ0candidates are kinematicallyﬁt with their mass constrained to the nominalπ0mass[4].Neutral kaons are reconstructed from pairs of oppositely charged tracks with the invariant mass within10MeV(∼3σ)from the nominal K0mass.We also require that the ratio between theﬂight length distance in the plane transverse to the beams direction and its uncertainty is greater than 3.The invariant mass of a D0candidate,m(D0),must be within3σof the D0mass.The D0mass resolutionσis about7.5MeV in the K−π+,K−K+andπ−π+modes,and about21MeV in the π0mode.Selected D0candidates areﬁtted with a constraint to the nominal D0mass.K0SWe reconstruct B meson candidates by combining a D0candidate with a track h−.For the K−π+mode,the charge of the track h−must match that of the kaon from the D0me-son decay.We select B meson candidates by using the beam-energy-substituted mass m ES=rejects more than90%of the continuum background while retaining77%of the signal in the K−π+, K−K+and K0π0modes and65%in theπ−π+channel.SMultiple B−→D0h−candidates are found in about4%of the events for the K0Sπ0and in less than1%of the events for the other D0decays.In these events aχ2is constructed from m(π0)(for K0Sπ0only),m(D0),and m ES and only the candidate with the smallestχ2is retained.The total reconstruction eﬃciencies,based on simulated signal events,are about33%(K−π+),28%(K−K+), 26%(π−π+)and17%(K0Sπ0).The main contributions to the BB events,in which the prompt track is either a pion or a kaon.The input variables to theﬁt are∆E and a particle identiﬁcation probability for the prompt track based on the Cherenkov angleθC,the momentum p and the polar angleθof the track.The extended likelihood function L is deﬁned asL=exp −M i=1n i N j=1 M i=1n i P i(∆E,θC; αi) ,(3)where N is the total number of observed events.The M functions P i(∆E,θC; αi)are the probability density functions(PDFs)for the variables∆E,θC,given the set of parameters αi.Since these two quantities are suﬃciently uncorrelated,their probability density functions are evaluated as a product P i=P i(∆E; αi)×P i(θC; αi).The∆E distribution for B−→D0K−signal events is parametrized with a Gaussian function. The∆E distribution for B−→D0π−is parametrized with the same Gaussian used for B−→D0K−with a relative shift of the mean,computed event by event as a function of the prompt track momentum,arising from the wrong mass assignment to the prompt track.The oﬀset and width of the Gaussian are keptﬂoating in theﬁt and are determined from data together with the yields.The∆E distribution for the continuum background is parametrized with a linear function whose slope is determined from oﬀ-resonance data.The∆E distribution for the B4PHYSICS RESULTS AND SYSTEMATIC STUDIESThe results of theﬁt are summarized in Table1.Figure1shows the distributions of∆E for the K−π+,CP+and CP−modes after enhancing the B→D0K purity by requiring that the prompt track be consistent with the kaon hypothesis.This requirement is about95%eﬃcient for the B−→D0K−signal while retaining only4%of the B−→D0π−candidates.The projection of a likelihoodﬁt,modiﬁed to take into account the tighter selection criteria,is overlaid in theﬁgure. Table1:Results of the B−→D0K−and B−→D0π−yields from the maximum-likelihoodﬁt on data.D0mode N(B→D0π)N(B→D0K)N(B−→D0K−)N(B+→K−π+11930±120897±34441±24456±25K0Sπ01248±4076+13−1246+10−930+9−8The double ratios R±are computed by scaling the ratios of the numbers of B−→D0K−and B−→D0π−mesons by correction factors(ranging from0.997to1.020depending on the D0mode) that account for small diﬀerences in the eﬃciency between the B−→D0K−and B−→D0π−selec-tions,estimated with simulated signal samples.The results are listed in Table2.The direct CP asymmetries A CP±for the B±→D0CP±K±decays are calculated from the measured yields of positive and negative charged meson decays and the results are reported in Table2.Table2:Measured double branching fraction ratios R±and CP asymmetries A CP±for diﬀerent D0decay modes.Theﬁrst error is statistical,the second is systematic.D0decay mode R CP/R A CPK−K+0.92±0.16±0.070.43±0.16±0.09π−π+0.70±0.29±0.090.27±0.40±0.09CP-even combined0.87±0.14±0.060.40±0.15±0.08The uncertainties in the branching fractions of the channels contributing to the B[6]Belle Collaboration,K.Abe et al.,Phys.Rev.D6*******(2002);B A B A R Collaboration,B.Aubert et al.,hep-ex/0308065,submitted to Phys.Rev.Lett..[7]B A B A R Collaboration,B.Aubert et al.,Phys.Rev.Lett.92202002(2004).Figure1:∆E distributions of B−→D0h−candidates,where a charged kaon mass hypothesis is assumed for h.Events are enhanced in B−→D0K−purity by requiring the Cherenkov angle of the track h to be within2σof the kaon hypothesis.Top:B−→D0[K−π+]K−;middle:B−→π0]K−.Solid curves represent projections of D0CP+[K−K+,π−π+]K−;bottom:B−→D0CP−[K0Sthe maximum likelihoodﬁt;dashed-dotted,dotted and dashed curves represent the B→D0K,B→D0πand background contributions.。

, Sigma 0

Page 2
Created: 7/18/1996 18:28
?1 ?2 ?3
e+ e? a] A theoretical value using QED.
VALUE <0:03
?
?
0 RANCHING RATIOS
/?total
CL%
VALUE 0:00545
? e + e ? /?total
?
90
DOCUMENT ID
COLAS
75 HLBC 58 Theoretical QED calculation
Review of Particle Physics: R.M. Barnett et al. (Particle Data Group), Phys. Rev. D54, 1 (1996)
0
1 I (J P ) = 1( 2 + ) Status:
The spin and parity have not been measured directly. They are of course assumed to be the same as for the + and ? .
VALUE ( N ) DOCUMENT ID TECN COMMENT VALUE (10?20 s) DOCUMENT ID TECN COMMENT
( 0 ! ) TRANSITION MAGNETIC MOMENT

Page 1
Created: 7/18/1996 18:28
The t uses + , 0 , ? , and massand mass-di erencemeasurements. 1192:55 0:08 OUR FIT Error includes scale factor of 1.2.

检验专业英语试题及答案

检验专业英语试题及答案一、选择题（每题2分，共20分）1. Which of the following is not a routine test in clinical laboratory?A. Blood countB. Urine analysisC. Liver function testD. DNA sequencing2. The term "hemoglobin" refers to:A. A type of proteinB. A type of enzymeC. A type of hormoneD. A type of lipid3. What is the primary function of the enzyme amylase?A. To break down proteinsB. To break down carbohydratesC. To break down fatsD. To break down nucleic acids4. The process of identifying the presence of a specific microorganism in a sample is known as:A. CulturingB. IsolationC. IdentificationD. Quantification5. Which of the following is a common method for measuring the concentration of glucose in blood?A. SpectrophotometryB. ChromatographyC. ElectrophoresisD. Enzymatic assay6. The term "ELISA" stands for:A. Enzyme-Linked Immunosorbent AssayB. Electrophoresis-Linked Immunosorbent AssayC. Enzyme-Linked Immunofluorescence AssayD. Electrophoresis-Linked Immunofluorescence Assay7. In medical diagnostics, what does "PCR" refer to?A. Polymerase Chain ReactionB. Protein Chain ReactionC. Particle Count ReactionD. Pathogen Characterization Reaction8. The process of measuring the amount of a specific substance in a sample is known as:A. TitrationB. CalibrationC. QuantificationD. Qualification9. Which of the following is a common type of clinical specimen?A. BloodB. SoilC. HairD. Water10. The term "antibodies" refers to:A. Proteins that recognize and bind to specific antigensB. Substances that neutralize toxinsC. Hormones that regulate immune responseD. Cells that produce immune responses二、填空题（每空1分，共10分）1. The process of separating molecules based on their size is known as __________.2. In clinical chemistry, the term "assay" refers to a__________ method.3. The unit of measurement for pH is __________.4. A common method for detecting the presence of antibodies in a sample is the __________ test.5. The process of identifying the type of bacteria in a sample is known as __________.6. The process of separating DNA fragments based on their size is known as __________.7. The term "ELISA" is used in __________ to detect the presence of specific antibodies or antigens.8. The process of identifying the genetic makeup of an organism is known as __________.9. The process of measuring the amount of a substance in a sample using a specific wavelength of light is called__________.10. The process of identifying the presence of specific microorganisms in a sample is known as __________.三、简答题（每题5分，共20分）1. Describe the principle of the Enzyme-Linked Immunosorbent Assay (ELISA).2. Explain the importance of maintaining aseptic technique ina clinical laboratory.3. What are the steps involved in performing a blood count?4. Discuss the role of antibodies in the immune response.四、论述题（每题15分，共30分）1. Compare and contrast the methods of Chromatography and Electrophoresis in terms of their applications in clinical diagnostics.2. Discuss the ethical considerations in the use of genetic testing for medical purposes.五、翻译题（每题5分，共10分）1. 将以下句子从中文翻译成英文：在临床实验室中，酶联免疫吸附测定法是一种常用的检测特定抗体或抗原的方法。

Vub from Exclusive Semileptonic B to pi Decays

a School
arXiv:hep-ph/0703284v2 17 May 2007
Abstract
We use Omn` es representations of the form factors f+ and f0 for exclusive semileptonic B → π decays, paying special attention to the treatment of the B∗ pole and its effect on f+ . We apply them to combine experimental partial branching fraction information with theoretical calculations of both form factors to extract |Vub |. The precision we achieve is competitive with the inclusive determination and we do not ﬁnd a signiﬁcant discrepancy between our result, |Vub | = (3.90 ± 0.32 ± 0.18) × 10−3 , and the inclusive world average value, (4.45 ± 0.20 ± 0.26) × 10−3 [1].
SHEP–0710
|Vub| from Exclusive Semileptonic B → π Decays
Jonathan M Flynna and Juan Nievesb
of Physics and Astronomy, University of Southampton Highﬁeld, Southampton SO17 1BJ, UK b Departay Nuclear, Universidad de Granada, E–18071 Granada, Spain

奶粉中饱和烃与芳香烃矿物油的高灵敏检测方法建立

刘玲玲，李冰宁，杨梦奇，等. 奶粉中饱和烃与芳香烃矿物油的高灵敏检测方法建立[J]. 食品工业科技，2023，44（20）：298−304.doi: 10.13386/j.issn1002-0306.2022110159LIU Lingling, LI Bingning, YANG Mengqi, et al. Development of A Highly Sensitive Method for the Determination of Mineral Oil Saturated Hydrocarbons (MOSH) and Aromatic Hydrocarbons (MOAH) in Milk Powder[J]. Science and Technology of Food Industry,2023, 44(20): 298−304. (in Chinese with English abstract). doi: 10.13386/j.issn1002-0306.2022110159· 分析检测 ·奶粉中饱和烃与芳香烃矿物油的高灵敏检测方法建立刘玲玲，李冰宁，杨梦奇，李　婷，武彦文*（北京市科学技术研究院分析测试研究所（北京市理化分析测试中心），北京 100094）摘　要：近年来，奶粉，特别是婴幼儿配方奶粉中的矿物油污染受到公众关注，相关国际监管逐渐升级。

然而，目前还没有针对奶粉中矿物油的标准检测方法。

本文依据欧盟的限量规定和分析要求，改进和优化了样品前处理方法，依次采用皂化法、正己烷提取、硅胶净化、环氧化反应方法，最后利用高效液相色谱-气相色谱联用技术（HPLC-GC ）建立了奶粉中饱和烃矿物油（MOSH ）和芳香烃矿物油（MOAH ）的高灵敏检测方法。

结果表明，该方法的定量限（LOQ ）达到0.5 mg/kg ，回收率为81.1%~112.0%（RSD=0.3%~3.8%），满足欧洲联合研究中心（JRC ）的方法要求。

Exact Hausdorff measure on the boundary of a Galton--Watson tree

1. Introduction. An interesting history of the classical problem of determining the Hausdorﬀ and packing dimensions and then the exact Hausdorﬀ and packing measures of the boundary of a supercritical Galton–Watson tree is found in the previous paper [46]. It was initiated in 1973 by the thesis of Holmes [18], whose supervisor and examiner were C. A. Rogers and S. J. Taylor, respectively. The author [46] completely solved the problem of determining the exact packing measure of the boundary of the tree by ﬁlling the critical gap in the proof of the theorem of Liu [22], which had been pointed out by Berlinkov and Mauldin [4]. Berlinkov [3] independently studied the exact packing measures of homogeneous random recursive fractals and, as a corollary, he obtained an analogous result under a certain additional assumption on the tree. However, it was stated without precise proof and he could not identify the explicit value of the exact packing measure of the boundary. Upon an outline of Hawkes [17], the author [46] deﬁned a random sequence {Y (n)} for n ≤ 0 as Y (−n) := µ(Bn ), that is, the branching

211080841_马氏副渤海鸟（鸟翼类：反鸟类_）新标本对鸟类头骨早期演化的意义

古脊椎动物学报V ERTEBRATA P AL A SIATICA DOI: 10.19615/ki.2096-9899.230217A new specimen of Parabohaiornis martini (Avialae: Enantiornithes) sheds light on early avian skull evolutionWANG Min(Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences , Institute of Vertebrate Paleontology and Paleoanthropology , Chinese Academy of SciencesAbstract The Enantiornithes is the most speciose clade of Mesozoic avialans with over 60named taxa reported from most continents that span the whole Cretaceous. Most of the fossilremains of this clade, as well as those of other early diverging avialans are preserved in two-dimensions. This complicates efforts to extract detailed anatomical information from the skull, inwhich the composite elements are delicate and thus not easily observable through conventionalmethods. The scarcity of well-preserved early avialan skulls, as well as the limited numberof specimens that have been analyzed using computed tomography scanning, consequentlycircumscribes a large morphological gap in the fossil record during the transition from the heavyand akinetic dinosaurian skull to the lightweight and kinetic bird skull. Here, we present a three-dimensional digital reconstruction of the skull and part of the cervical vertebrae of a new specimenof the enantiornithine Parabohaiornis martini from the Early Cretaceous of China. Our resultsdemonstrate that Parabohaiornis retains the plesiomorphic non-avialan dinosaurian temporal andpalatal configurations, reinforcing the recent hypothesis that the temporal and palatal regions areevolutionarily conservative and that the akinetic skull has been conserved well into diversificationof early branching avialans.Key words Enantiornithes, Avialae, Bohaiornithidae, cranium, cranial kinesisCitation Wang M, 2023. A new specimen of Parabohaiornis martini (Avialae: Enantiornithes) sheds light on early avian skull evolution. Vertebrata PalAsiatica, 61(2): 90–1071 IntroductionThe Bohaiornithidae is currently recognized as the most diverse enantiornithine family and encompasses six known genera and species (Bohaiornis guoi , Sulcavis geeorum , Zhouornis hani , Shenqiornis mengi , Parabohaiornis martini , Longusunguis kurochkini ) that persisted at least five million years (125–120 Ma) (Wang et al., 2014a; Hu et al., 2020), which provides a rare chance to investigate taxonomical and morphological diversity during the early evolution of the Enantiornithes. Bohaiornithids also display several morphological features国家自然科学基金杰出青年基金(批准号：42225201)、中国科学院前沿科学重点研究计划从“0到1”原始创新十年择优项目(编号：ZDBS-LY-DQC002)和腾讯科学探索奖资助。

GMAT网络课堂阅读笔记-王昆嵩主讲7

Passage 1In choosing a method for determining climatic condi-tions that existed in the past, paleoclimatologists invoke four principal criteria. First, the material-rocks, lakes,vegetation, etc.-on which the method relies must be ( 5 )widespread enough to provide plenty of information, since analysis of material that is rarely encountered will not permit correlation with other regions or with otherperiods of geological history. Second, in the process offormation, the material must have received an environ- (10) mental signal that reflects a change in climate and thatcan be deciphered by modern physical or chemicalmeans. Third, at least some of the material must haveretained the signal unaffected by subsequent changes in the environment. Fourth, it must be possible to deter- (15) mine the time at which the inferred climatic conditionsheld. This last criterion is more easily met in datingmarine sediments, because dating of only a smallnumber of layers in a marine sequence allows the age of other layers to be estimated fairly reliably by extrapola- (20) tion and interpolation. By contrast, because sedimenta-tion is much less continuous in continental regions, esti- mating the age of a continental bed from the knownages of beds above and below is more risky.One very old method used in the investigation of past (25) climatic conditions involves the measurement of waterlevels in ancient lakes. In temperate regions, there areenough lakes for correlations between them to give us a reliable picture. In arid and semiarid regions, on theother hand, the small number of lakes and the great (30) distances between them reduce the possibilities for corre-lation. Moreover, since lake levels are controlled by rates of evaporation as well as by precipitation, the interpreta-tion of such levels is ambiguous. For instance, the factthat lake levels in the semiarid southwestern United (35) States appear to have been higher during the last ice agethan they are now was at one time attributed toincreased precipitation. On the basis of snow-line eleva-tions, however, it has been concluded that the climatethen was not necessarily wetter than it is now, but rather (40) that both summers and winters were cooler, resulting inreduced evaporation.Another problematic method is to reconstruct formerclimates on the basis of pollen profiles. The type of vege- tation in a specific region is determined by identifying (45) and counting the various pollen grains found there.Although the relationship between vegetation andclimate is not as direct as the relationship betweenclimate and lake levels, the method often works well inthe temperate zones. In arid and semiarid regions in (50) which there is not much vegetation, however, smallchanges in one or a few plant types can change thepicture dramatically, making accurate correlationsbetween neighboring areas difficult to obtain.1. Which of the following statements about the difference between marine and continental sedimentation is supported by information in the passage?(A) Data provided by dating marine sedimentation is more consistent with researchers' findings inother disciplines than is data provided by dating continental sedimentation.(B) It is easier to estimate the age of a layer in a sequence of continental sedimentation than itis to estimate the age of a layer in a sequenceof marine sedimentation.(C) Marine sedimentation is much less widespread than continental sedimentation.(D) Researchers are more often forced to rely on extrapolation when dating a layer of marine sedimentation than when dating a layer ofcontinental sedimentation.(E) Marine sedimentation is much more continuous than is continental sedimentation.2. Which of the following statements best describes the organization of the passage as a whole?(A) The author describes a method for determining past climatic conditions and then offers specificexamples of situations in which it has been used. (B) The author discusses the method of dating marine and continental sequences and then explains howdating is more difficult with lake levels than withpollen profiles.(C) The author describes the common requirements of methods for determining past climatic conditionsand then discusses examples of such methods.(D) The author describes various ways of choosing a material for determining past climatic conditionsand then discusses how two such methods have yielded contradictory data.(E) The author describes how methods for determining past climatic conditions were first developed andthen describes two of the earliest known methods.3. It can be inferred from the passage that paleoclimatologists have concluded which of the following on the basis of their study of snow-line elevations in the southwestern United States?(A) There is usually more precipitation during an ice age because of increased amounts of evaporation.(B) There was less precipitation during the last ice age than there is today.(C) Lake levels in the semiarid southwestern United States were lower during the last ice age than theyare today.(D) During the last ice age, cooler weather led to lower lake levels than paleoclimatologists had previously assumed.(E) The high lake levels during the last ice age may havebeen a result of less evaporation rather than more precipitation.4. Which of the following would be the most likely topic for a paragraph that logically continues the passage?(A) The kinds of plants normally found in arid regions(B) The effect of variation in lake levels on pollen distribution(C) The material best suited to preserving signals of climatic changes(D) Other criteria invoked by paleoclimatologists when choosing a method to determine past climatic conditions(E) A third method for investigating past climatic conditions5. The author discusses lake levels in the southwestern United States in order to(A) illustrate the mechanics of the relationship between lake level, evaporation, and precipitation(B) provide an example of the uncertainty involved in interpreting lake levels(C) prove that there are not enough ancient lakes with which to make accurate correlations(D) explain the effects of increased rates of evaporation on levels of precipitation(E) suggest that snow-line elevations are invariably more accurate than lake levels in determining ratesof precipitation at various points in the past6. It can be inferred from the passage that an environmental signal found in geological materialwould not be useful to paleoclimatologists if it(A) had to be interpreted by modern chemical means(B) reflected a change in climate rather than a long-term climatic condition(C) was incorporated into a material as the material was forming(D) also reflected subsequent environmental changes(E) was contained in a continental rather than a marine sequence7. According to the passage, the material used to determine past climatic conditions must be widespread for whichof the following reasons?Ⅰ.Paleoclimatologists need to make comparisons between periods of geological history.Ⅱ. Paleoclimatologists need to compare materials that have supported a wide variety of vegetation.Ⅲ. Paleoclimatologists need to make comparisons with data collected in other regions.(A) Ⅰonly(B) Ⅱonly(C) Ⅰand Ⅱonly(D) Ⅰand Ⅲonly(E) Ⅱand Ⅲonly8. Which of the following can be inferred from the passage about the study of past climates in arid and semiaridregions?(A) It is sometimes more difficult to determine pastclimatic conditions in arid and semiarid regions thanin temperate regions.(B) Although in the past more research has been done on temperate regions, paleoclimatologists haverecently turned their attention to arid and semiaridregions.(C) Although more information about past climates canbe gathered in arid and semiarid than in temperate regions, dating this information is more difficult.(D) It is difficult to study the climatic history of arid and semiarid regions because their climates have tendedto vary more than those of temperate regions.(E) The study of past climates in arid and semiaridregions has been neglected because temperateregions support a greater variety of plant and animallife.Passage 2Australian researchers have discovered electroreceptors (sensory organs designed to respond to electrical fields) clustered at the tip of the spiny anteater's snout. The researchers made this discovery by exposing small areas of (5) the snout to extremely weak electrical fields and recording the transmission of resulting nervous activity to the brain. While it is true that tactile receptors, another kind of Sensory organ on the anteater's snout, can also respond toelectrical stimuli, such receptors do so only in response to(10) electrical field strengths about 1,000 times greater thanthose known to excite electroreceptors.Having discovered the electroreceptors, researchers arenow investigating how anteaters utilize such a sophisticatedsensory system. In one behavioral experiment, researchers(15) successfully trained an anteaters to distinguish betweentwo troughs of water, one with a weak electrical fieldand the other with none. Such evidence is consistent withresearchers' hypothesis that anteaters use electroreceptorsto detect electrical signals given off buy prey; however,(20) researchers as yet have been unable to detect electricalsignals emanating from termite mounds, where the favoritefood of anteaters live. Still, researchers have observedanteaters breaking into a nest of ants at an oblique angleand quickly locating nesting chambers. This ability quickly(25) to locate unseen prey suggests, according to the researchers,that the anteaters were using their electroreceptors tolocate the nesting chambers.1. According to the passage, which of the following is a characteristic that distinguishes electroreceptors from tactile receptors?(A) The manner in which electroreceptors respond to electrical stimuli(B) The tendency of electroreceptors to be found in clusters(C) The unusual locations in which electroreceptors are found in most species.(D) The amount of electrical stimulation required to excite electroreceptors(E) The amount of nervous activity transmitted it the brain by electroreceptors when they are excited2. Which of the following can be inferred about experiment described in the first paragraph?(A) Researchers had difficulty verifying the existence of electroreceptors in the anteater because electroreceptors respond to such a narrow range of electrical field strengths. (B) Researchers found that the level of nervous activity in the anteater's brain increased dramatically as the strength of the electrical stimulus was increased.(C) Researchers found that some areas of the anteater's snout were not sensitive to a weak electrical stimulus.(D) Researchers found that the anteater's tactile receptors were more easily excited by a strong electrical stimulus than were the electroreceptors.(E) Researchers tested small areas of the anteater's snout in order to ensure that only electroreceptors were responding to the stimulus.3. The author of the passage most probably discussed the function of tactile receptors (lines 7-11) in order to(A) eliminate and alternative explanation of anteater's response to electrical stimuli(B) highlight a type of sensory organ that has a function identical to that of electroreceptors(C) point out a serious complication in the research on electroreceptors in anteaters(D) suggest that tactile receptors assist electroreceptors in the detection of electrical signals(E) introduce a factor that was not addressed in research on electroreceptors in anteaters4. Which of the following can be inferred about anteaters from the behavioral experiment mentioned in the second paragraph?(A) They are unable to distinguish between stimuli detected by their tactile receptors.(B) They are unable to distinguish between the electrical signals emanating from termite mounds and those emanating from ant nests.(C) They can be trained to recognize consistently the presence of a particular stimulus.(D) They react more readily to strong than to weak stimuli.(E) They are more efficient at detecting stimuli in a controlled environment than in a natural environment.5. The passage suggests that researchers mentioned in the second paragraph who observed anteaters break into a nest of ants would most likely agree with which of the following statements?(A) The event they observed provides conclusive evidence that anteaters use their electroreceptors to locate unseen prey.(B) The event they observed was atypical and may not reflect the usual hunting practices of anteaters.(C) It is likely that the anteaters located the ants' nesting chambers without the assistance of electroreceptors.(D) Anteaters possess a very simple sensory system for use in locating prey.(E) The speed with which the anteaters located their prey is greater than what might be expected on the basis of chance alone.6. Which of the following, if true, would most strengthen the hypothesis mentioned in lines 17-19?(A) Researchers are able to train anteaters to break into an underground chamber that is emitting a strong electrical signal.(B) Researchers are able detect a weak electrical signal emanating from the nesting chamber of an ant colony.(C) Anteaters are observed taking increasingly longer amounts of time to locate the nesting chambers of ants.(D) Anteaters are observed using various angles to break into nests of ants.(E) Anteaters ate observed using the same angle used with nests of ants to break into the nests of other types of prey.Passage 3Most economists in the United States seemcaptivated by the spell of the free market. Conse-quently, nothing seems good or normal that doesnot accord with the requirements of the free market. ( 5 )A price that is determined by the seller or, for that matter, established by anyone other than theaggregate of consumers seems pernicious. Accord- ingly, it requires a major act of will to think ofprice-fixing (the determination of prices by the (10) seller) as both normal and having a valuableeconomic function. In fact, price-fixing is normalin all industrialized societies because the indus-trial system itself provides, as an effortless conse-quence of its own development, the price-fixing (15) that it requires. Modern industrial planningrequires and rewards great size. Hence,a comparatively small number of large firms willbe competing for the same group of consumers.That each large firm will act with consideration of (20) its own needs and thus avoid selling its productsfor more than its competitors charge is commonlyrecognized by advocates of free-market economictheories. But each large firm will also act withfull consideration of the needs that it has in(25) common with the other large firms competing forthe same customers. Each large firm will thusavoid significant price-cutting, because price-cutting would be prejudicial to the common interestin a stable demand for products. Most economists (30) do not see price-fixing when it occurs becausethey expect it to be brought about by a number ofexplicit agreements among large firms; it is not.Moreover, those economists who argue thatallowing the free market to operate without inter- (35) ference is the most efficient method of establishingprices have not considered the economies of non-socialist countries other than the United states.These economies employ intentional price-fixing,usually in an overt fashion. Formal price-fixing (40) by cartel and informal price-fixing by agreementscovering the members of an industry are common-place. Were there something peculiarly efficientabout the free market and inefficient about price-fixing, the countries that have avoided the first (45) and used the second would have suffered drasticallyin their economic development. There is no indica-tion that they have.Socialist industry also works within a frame-work of controlled prices. In the early 1970's, (50) the Soviet Union began to give firms and industriessome of the flexibility in adjusting prices that amore informal evolution has accorded the capitalistsystem. Economists in the United States havehailed the change as a return to the free market. (55) But Soviet firms are no more subject to pricesestablished by a free market over which theyexercise little influence than are capitalist firms;rather, Soviet firms have been given the power tofix prices.1. The primary purpose of the passage is to(A) refute the theory that the free market plays auseful role in the development of industrialized societies(B) suggest methods by which economists and members of the government of the United States canrecognize and combat price-fixing by large firms(C) show that in industrialized societies price-fixing and the operation of the free market are not only compatible but also mutually beneficial(D) explain the various ways in which industrialized societies can fix prices in order to stabilize the free market(E) argue that price-fixing, in one form or another, is an inevitable part of and benefit to the economy of any industrialized society2. The passage provides information that would answer which of the following questions about price-fixing?Ⅰ.What are some of the ways in which prices can be fixed?Ⅱ. For what products is price-fixing likely to be more profitable than the operation of the free market?Ⅲ.Is price-fixing more common in socialist industrialized societies or in nonsocialist industrialized societies?(A) Ⅰonly(B) Ⅲonly(C) Ⅰand Ⅱonly(D) Ⅱand Ⅲonly(E) Ⅰ,Ⅱ,and Ⅲ3. The author's attitude toward Most economists in the United States(line 1) can best be described as(A) spiteful and envious(B) scornful and denunciatory(C) critical and condescending(D) ambivalent but deferential(E) uncertain but interested4. It can inferred from the author's argument that a price fixed by the seller seems pernicious(line 7) because(A) people do not have confidence in large firms(B) people do not expect the government toregulate prices(C) most economists believe that consumers as a group should determine prices(D) most economists associate fixed prices with communist and socialist economies(E) most economists believe that no one groupshould determine prices5. The suggestion in the passage that price-fixing in industrialized societies is normal arises from theauthor's statement that price-fixing is(A) a profitable result of economic development(B) an inevitable result of the industrial system(C) the result of a number of carefully organized decisions(D) a phenomenon common to industrialized and nonindustrialized societies(E) a phenomenon best achieved cooperatively by government and industry6. According to the author, price-fixing in nonsocialist countries is often(A) accidental but productive(B) illegal but useful(C) legal and innovative(D) traditional and rigid(E) intentional and widespread7. According to the author, what is the result of the Soviet Union's change in economic policy in the 1970's?(A) Soviet firms show greater profit.(B) Soviet firms have less control over the free market.(C) Soviet firms are able to adjust to technological advances.(D) Soviet firms have some authority to fix prices.(E) Soviet firms are more responsive to the free market.8. With which of the following statements regarding the behavior of large firms in industrialized societieswould the author be most likely to agree?(A) The directors of large firms will continue to anticipate the demand for products.(B) The directors of large firms are less interested in achieving a predictable level of profit than inachieving a large profit.(C) The directors of large firms will strive to reduce the costs of their products.(D) Many directors of large firms believe that the government should establish the prices that will be charged for products.(E) Many directors of large firms believe that the price charged for products is likely to increase annually.9. In the passage, the author is primarily concerned with(A) predicting the consequences of a practice(B) criticizing a point of view(C) calling attention to recent discoveries(D) proposing a topic for research(E) summarizing conflicting opinionsKEYSPassage 1: ECEEB DDAPassage 2: DCACE BPassage 3: EACCB EDAB。

测绘工程专业英语课文翻译

Unit 9 Basic Statistical Analysis of Random Errors （随机误差的统计学基本分析）Random errors are those variables that remain after mistakes are detected and eliminated and all systematic errors have been removed or corrected from the measured values.（随机误差是在错误被察觉【detect】和消除【eliminate】后，并且所有系统误差被从测量值中移除或修正后，保留下的那些变量【variable变量、变化n.】）They are beyond the control of the observer.（它们是观测者无法控制的）So the random errors are errors the occurrence of which does not follow a deterministic pattern.（因此随机误差是不遵循某个确定性【deterministic 确定性的】模式【pattern】而发生的误差）In mathematical statistics, they are considered as stochastic variables, and despite their irregular behavior, the study of random errors in any well-conducted measuring process or experiment has indicated that random errors follow the following empirical rules:（在数理统计【mathematical statistics】中，它们被当成随机变量【stochastic variable】，尽管它们的行为无规律，在任一正确的【well-conducted原意为品行端正的，这里指测量实验和活动是无误的】测量活动和实验中，对的随机误差的研究显示【indicate】随机误差遵循以下经验法则【empirical rule】：）⑴A random error will not exceed a certain amount.（随即误差不会超过一个确定的值）⑵Positive and negative random errors may occur at the same frequency.（正负误差出现的频率相同）⑶Errors that are small in magnitude are more likely to occur than those that are larger in magnitude.（误差数值【magnitude量值、大小】小的比数值大的误差出现可能性大【be likely to 可能】）⑷The mean of random errors tends to zero as the sample size tends to infinite.（当【as】样本大小【sample size】趋近于无穷【infinite】时，随机误差的平均值趋近于0）In mathematical statistics, random errors follow statistical behavioral laws such as the laws of probability.（在数理统计中，随机误差遵循统计学的【statistical】行为【behavioral行为的】规律，如概率法则）A characteristic theoretical pattern of error distribution occurs upon analysis of a large number of repeated measurements of a quantity, which conform to normal or Gaussian distribution.（发生在一个量的大量重复观测分析【analysisn.】中的误差分布的一个特征理论模式，遵照【conform to遵照】正态或高斯分布）【在对一个量进行大量重复观测分析后，得到一个误差分布的理论特征——正态或高斯分布】The plot of error sizes versus probabilities would approach a smooth curve of the characteristic bell-shape.（误差大小与【versus与、与……的关系、与……相对】概率的关系图，接近一条光滑的特有的【characteristic 特有的】钟形曲线。

Effect of metal films on the photoluminescence and electroluminescence of conjugated polymers

Effect of metalﬁlms on the photoluminescence and electroluminescence of conjugated polymersH.Becker,S.E.Burns,and R.H.FriendCavendish Laboratory,Madingley Road,Cambridge CB30HE,United Kingdom͑Received12February1997;revised manuscript received15April1997͒We report the modiﬁcation of photoluminescence͑PL͒and electroluminescence͑EL͒from conjugatedpolymers due to the proximity of metalﬁlms.The presence of a metalﬁlm alters the radiative decay rate of anemitter via interference effects,and also opens up an efﬁcient nonradiative decay channel via energy transferto the metalﬁlm.We show that these effects lead to substantial changes in the PL and EL quantum efﬁcienciesand the emission spectra of the polymers studied here͓cyano derivatives of poly͑p-phenylenevinylene͒,PPV͔as a function of the distance of the emitting dipoles from the metalﬁlm.We have measured the PL quantumefﬁciency directly using an integrating sphere,and found its distance dependence to be in good agreement withearlier theoretical ing the spectral dependence of the emission,we have been able to investigatethe effect of interference on the radiative rate as a function of the wavelength and the distance between theemitter and the mirror.We compare our results with simulations of the radiative power of an oscillating dipolein a similar system.From our results we can determine the orientation of the dipoles in the polymerﬁlm,andthe branching ratio that gives the fraction of absorbed photons leading to singlet excitons.We propose designrules for light-emitting diodes͑LED’s͒and photovoltaic cells that optimize the effects of the metalﬁlm.Bymaking optimum use of above effects we have substantially increased the EL quantum efﬁciencies of PPV/cyano-PPV double-layer LED’s.͓S0163-1829͑97͒09228-X͔I.INTRODUCTIONConjugated polymers have attracted much attention since the discovery that these materials can be used as emissive layers in light emitting diodes͑LED’s͒.1,2Research has been particularly focused on poly͑p-phenylenevinylene͒͑PPV͒and its derivatives because of their high efﬁciencies.With these materials a wide range of emission colors and elec-troluminescence efﬁciencies up to4%have been reported.3 The competition between radiative and nonradiative decay processes in conjugated polymers is currently of great inter-est since it governs the efﬁciency of light emission in conju-gated polymer devices such as LED’s and lasers as well as the quantum yield of photovoltaic devices.1,4–7Most of these devices contain metalsﬁlms either as electrodes for charge injection in electroluminescent devices or as mirrors in order to manipulate the radiative properties of the emissive species in the polymer.The presence of a metalﬁlm will always inﬂuence the properties of the emitting material.Microcavi-ties have been used to narrow the linewidth and tune the color of emission from conjugated polymers.8–10It has re-cently been shown that the spontaneous emission rate can be greatly enhanced or suppressed in metal mirror microcavity structures containing conjugated polymers,depending on the overlap of the electric-ﬁeld distribution within the microcav-ity with the emissive layer.11,12It has also been demonstrated that enhancement of the stimulated emission rate leading to lasing can be achieved with conjugated polymers using simi-lar microcavity structures.7More generally,the radiative and nonradiative rates of an excited dipoleﬂuorescing in front of a metalﬁlm or between two metalﬁlms have been extensively investigated,both theoretically and experimentally.13–20The luminescence life-time␶is related to the rate constants for radiative(k R)and nonradiative(k NR)decay by1␶ϭk Rϩk NR,͑1͒where the radiative lifetime is1/k R,and the nonradiative lifetime is1/k NR.The quantum efﬁciency for luminescence q is given byqϭbͩk R k Rϩk NRͪ,͑2͒where the branching ratio b is the fraction of absorbed pho-tons leading to singlet excitons.The balance between the radiative and the nonradiative decay rates therefore deter-mines the luminescence efﬁciency.Different methods have been used to predict the lifetime and luminescence quantum efﬁciency for an excited molecule in front of a mirror.The interference method successfully predicts the effects of a re-ﬂective surface on the radiative properties of the dipole.15 However,at short distances nonradiative energy transfer to the metal becomes an effective decay channel for an excited molecule near a metal,thus increasing the nonradiative de-cay rate close to the metal.In the‘‘mechanical model’’14the excited molecule is considered as a harmonic oscillator with theﬁeld reﬂected by the metalﬁlm acting as a driving force on the oscillator.By introducing a reﬂection coefﬁcient smaller than unity and a phase factor into the perfect mirror equations,some of the aspects of nonradiative energy trans-fer could be reproduced.14However,the best agreement be-tween theory and experiment has been achieved with the energyﬂux method where the total energyﬂux through inﬁ-nite planes above and below the dipole is calculated.19It gives separate expressions for the effects of interference on the radiative lifetime and of nonradiative energy transfer on the nonradiative lifetime.The nature of the nonradiative en-ergy transfer depends on the distance of the oscillating dipolePHYSICAL REVIEW B15JULY1997-IIVOLUME56,NUMBER4560163-1829/97/56͑4͒/1893͑13͒/$10.001893©1997The American Physical Societyto the metal.The interaction of the dipole with the electron gas of the metal is dominated by scattering by the metal surface at short (Ͻ20nm)distances and scattering in the bulk,e.g.,by phonons or impurities,for longer distances.21,22The decay time of an emitting molecule in front of a metal ﬁlm has previously been reported.15,19,23In order to deduce the quantum efﬁciency from those measurements it was nec-essary to make assumptions about the orientation of the di-poles and the free-space efﬁciency of the emitting molecule.In this paper we present direct measurements of the photo-luminescence ͑PL ͒and electroluminescence ͑EL ͒quantum efﬁciencies of two cyanoderivatives of poly ͑p -phenylenevinylene ͒,MEH-CN-PPV and DHeO-CN-PPV,the structures of which are shown in Fig.1,and compare our results with the theoretical predictions for the quantum efﬁ-ciency of a dipole in front of a mirror.Measurements of the PL quantum efﬁciency rather than the luminescence lifetime are of particular relevance for electroluminescent devices.The effect of interference on the radiative properties of an excited molecule is dependent on the emission wavelength.This wavelength dependence is again a function of the dis-tance between the emitting molecule and the mirror.For broad bandwidth emitters such as conjugated polymers,this leads to substantial changes in the shape of the emission spectrum depending on the separation between the emitter and the mirror.We have investigated the changes in the PL emission spectrum of a 15–20-nm-thick MEH-CN-PPV ﬁlm separated by a SiO 2layer from a 35-nm-thick aluminium ﬁing a simple model that describes the effects of in-terference on the radiative rates,we have been able to relate the spectral shape of the emission to the radiative power of an oscillating dipole in front of a mirror as a function ofwavelength and distance between the polymer and the metal.We compare our results with earlier 24and recent simulations of the radiative power of an emitting dipole in front of a metal mirror.The internal electroluminescence efﬁciency of a LED is deﬁned as the number of emitted photons per charge carrier ﬂowing through the circuit.Because the light-emitting spe-cies is thought to be the same in EL and PL,we expect the effects of a metal ﬁlm on the EL to be the same as measured for the PL.The maximum EL efﬁciency of a device is ex-pected to be one-fourth of the PL efﬁciency of the emitting polymer where the factor 4derives from the spin degeneracy of the singlet and triplet excitons,with only the singlet exci-tons decaying radiatively.25So far,the highest EL efﬁcien-cies for polymer LED’s have been achieved with PPV/MEH-CN-PPV and PPV/DHeO-CN-PPV double-layer devices.3,26This has been attributed to various reasons,but it has been unclear what role interference effects and nonradiative en-ergy transfer to the metal electrode play.In these devices it has been proposed that emission occurs from a thin layer at the interface between the polymer layers,although there has been little direct evidence that this is the case.We have systematically changed the position of the interface between the two polymer layers relative to the metal ﬁlm.We mea-sured the dependence of the EL efﬁciency of PPV/MEH-CN-PPV double-layer devices on the distance between the polymer-polymer interface and the Al electrode.This allows us to comment on the effect of the Al ﬁlm on the radiative and nonradiative properties of the emitting species and the increased EL efﬁciencies in double-layer devices.We com-pare the EL efﬁciencies with the PL efﬁciencies measured on thin polymer ﬁlms separated from a 35-nm Al ﬁlm by a SiO 2layer.The interface between conjugated polymers and metals has recently been studied in order to obtain information about the chemistry that occurs at the interface and about diffusion of metal atoms into the near-surface region of the polymer.27The effects of these processes on PL and EL are important for device operation.It has also been reported that thin calcium ﬁlms efﬁciently quench the PL of thin conju-gated polymer ﬁlms if deposited on top of them.28In this context it is important to understand the origin and conse-quences of nonradiative energy transfer from the polymer to the metal and of interference effects on the quantum efﬁ-ciency and the emission spectrum.II.METHODA.Experimental proceduresWe have built three device structures as shown schemati-cally in Fig.2.Thin metal ﬁlms of Al or Au were thermally evaporated onto one-half of a quartz substrate.We used semitransparent Al and Au ﬁlms of thicknesses around 2–3nm with a transmittance of more than 70%in the visible,and 35-nm-thick nontransparent Al ﬁlms.Films of MEH-CN-PPV and DHeO-CN-PPV ͑Fig.1͒were prepared by spin coating onto the metal-coated substrates.A series of thick-nesses between 15and 200nm was prepared.On a second set of samples,transparent SiO 2spacer layers ͑Schott glass 8329͒of differing thicknesses were evaporated on top of the metal-ﬁlm coated substrates using an electron-beamevapo-FIG. 1.Chemical structures of PPV,MEH-CN-PPV,and DHeO-CN-PPV.189456H.BECKER,S.E.BURNS,AND R.H.FRIENDration technique.The refractive index of the glass was taken to be 1.47.A thin polymer layer of 15–20-nm thickness was then spin coated onto the SiO 2layer.In order to investigate the effect of indium-tin oxide ͑ITO ͒on the PL quantum ef-ﬁciency MEH-CN-PPV ﬁlms of different thicknesses were spin coated onto commercially-available ITO-coated glass substrates ͑Balzers ITO-coated glass substrates type 257;ITO layer thickness ϳ100nm ͒.The PL efﬁciency ͑number of photons emitted per number of photons absorbed ͒and the emission spectra of the PL samples ͑structures 1and 2,Fig.1͒were measured using an integrating sphere and a charge-coupled device ͑CCD ͒array spectrometer ͑Oriel Instaspec IV ͒.29,30A 458-nm laser served as the excitation source.The samples were illuminated from the polymer side.The PL efﬁciency and the PL spectrum were measured on the metal-coated half,and as a reference on the noncoated half of the sample as a function of the thickness of both the polymer ﬁlm and the SiO 2layer.A series of PPV/MEH-CN-PPV double-layer LED de-vices was built by spin-coating the PPV precursor onto ITO coated substrates.After thermal conversion of the PPV pre-cursor,MEH-CN-PPV was spin coated onto the PPV ﬁlm.Finally,Al electrodes were thermally evaporated on top of the structure.The PPV layer was 120nm thick.The thick-ness of the MEH-CN-PPV layer varied between 24and 110nm.A schematic diagram of the devices is shown in Fig.1.The electroluminescence in the forward direction was mea-sured using a calibrated photodiode.The batches of MEH-CN-PPV and DHeO-CN-PPV used showed PL quantum efﬁciencies between 33%and 39%when spin coated onto glass substrates.These are similar to those reported previously.29The samples were kept in a nitrogen-ﬁlled atmosphere or in vacuum at all times,and the experiments were performed within a few hours after the preparation of the samples in order to avoid oxidation of the polymer or the metal.B.ModelingSimulations of the radiative power of oscillating dipoles embedded in the top layer of a three-layer structure similar to structure 2shown in Fig.2were carried out using the transfer-matrix method and multilayer stack theory.The model is based entirely on classical electromagnetic theory,and is described in more detail in Ref.24.We simulated the radiative power of dipoles distributed uniformly throughout a 20-nm-thick layer separated from a 35-nm Al ﬁlm by a trans-parent layer with the same refractive index as the SiO 2that was used to build structure 2.The radiative power of the dipoles was normalized to be 1in free space.By integrating the emitted power over all angles,the changes in radiative rate due to the metal ﬁlm were calculated as a function of the distance between the emission layer and the metal,the wave-length and the orientation of the dipoles.The refractive index data for the aluminum was taken from Ref.31.The refractive index of MEH-CN-PPV was taken to be 1.7,where any bi-refringence and the dispersion of the refractive index was neglected.The refractive index of MEH-CN-PPV at 633nm has been measured to be 1.695for TM and 1.77for TE modes.32III.RESULTSA.PL spectra and PL efﬁciencyThe PL emission and absorption spectra of MEH-CN-PPV are shown in Fig.3.Due to the large Stokes’shift typical of this class of materials,the overlap between absorp-tion and emission is very small.For wavelengths above 550nm this allows us to use the spectra measured in the integrat-ing sphere,since reabsorption of the emitted light is low and the shape of the emission spectrum is therefore the same as for the free-space emission.1.Polymer on metal (structure 1)Figure 4shows the PL efﬁciency of MEH-CN-PPV and DHeO-CN-PPV ﬁlms in front of different metal ﬁlms as a function of the ﬁlm thickness.2-and 3-nm-thick gold and aluminum ﬁlms were used as well as 35-nm-thick aluminium ﬁlms.The data were corrected for the absorption of laser light by the metal mirror,which was calculated from the transmission spectra of the metal ﬁlms,simulations of the absorption of light by the metal,33the transmission spectra of the polymer ﬁlms,and the absorption by the whole structure measured in the integrating sphere.The 2–3-nm-thick metal ﬁlms are highly transparent for light in the visible range ͑Ͼ70%transmittance ͒.Hence we expect interferenceeffectsFIG.2.Schematic diagram of the PL ͑1,2͒and EL ͑3͒devicestructures.FIG.3.Normalized emission spectrum ͑solid line ͒and absorp-tion spectrum ͑dotted line ͒of MEH-CN-PPV.561895EFFECT OF METAL FILMS ON THE ...to play a minor role.Figure 5shows the spectra measured in the integrating sphere for MEH-CN-PPV ﬁlms of different thicknesses on 3nm of Al.We measured the absorption coefﬁcient for the MEH-CN-PPV at 458nm to be ␣ϭ1.24ϫ105cm Ϫ1,so that approxi-mately half of the excitation light is absorbed in the ﬁrst 56nm.Since the diffusion range for the excitons in these ma-terials is of the order of a few nanometers,we take the spatial distribution of the emission to be identical to the absorption proﬁle.For thick polymer ﬁlms,where most of the light is emitted in regions far away from the metal,the shape of the emission spectrum is the same as for thin ﬁlms,where the light is emitted close to the metal.This conﬁrms that inter-ference effects are negligible for 2–3-nm-thick metal ﬁlms.We see from our measurements that the PL is efﬁciently quenched for polymer ﬁlms up to a thickness of 90nm for thin metal ﬁlms,and up to 60nm for a thick Al ﬁlm.Within a critical distance of 20nm almost all luminescence is quenched.Figure 4also shows the dependence on the polymer ﬁlm thickness of the PL quantum efﬁciency of MEH-CN-PPVﬁlms deposited on 35nm of Al.The reﬂectance of the metal ﬁlm was around 90%.As shown in Fig.6,the shape of the emission spectrum changes with the polymer ﬁlm thickness due to interference effects.Surprisingly,the PL quantum ef-ﬁciency rises faster with polymer ﬁlm thickness than for thin metal ﬁlms.The difference in the distance dependence of the energy transfer rate to the metal cannot explain this.How-ever,interference effects not only affect the emission prop-erties of a material but also change the absorption in the same fashion.As we will see in Sec.III A 2,the radiative power of dipoles parallel to the mirror plane increases with the distance between the mirror and the dipole for distances comparable to the maximum MEH-CN-PPV ﬁlm thickness.We therefore expect the absorption of light to increase with distance from the metal.The majority of light is therefore absorbed and emitted further away from the metal than in the case of thin metal ﬁlms with a low reﬂectivity.As a conse-quence,the maximum PL efﬁciency is reached for thinner polymer ﬁlms.The same experiment was performed with polymer ﬁlms of differing thicknesses spin-coated on ITO-coated glass sub-strates.ITO,which is commonly used as a hole injector in electroluminescent devices,was not found to quench the PL for polymer ﬁlms thicker than 20nm.Only for a 20-nm-thick ﬁlm was a reduction of the PL efﬁciency of 12%observed.This might be explained in terms of exciton diffusion toward the polymer-ITO interface where the excitons are quenched.Our results are in agreement with reports in the literature.28,34,35Discussion .The suppression of light emission near the polymer metal interface cannot be explained by absorption of emitted light by the metal.Although this effect reduces the measured quantum efﬁciency,it is independent of the distance between the metal and the emitter,and can therefore not explain the increase in quantum efﬁciency with polymer ﬁlm thickness.At long distances the PL efﬁciency ap-proaches a constant value below the free-space quantum ef-ﬁciency of our samples.As we will see below this is consis-tent with our assumption that interference effects can be neglected for very thin metal ﬁlms.Our data agree qualita-tively with a calculation of the quantum yield of an oscillat-ing dipole with a quantum efﬁciency of unity in front ofaFIG.4.PL quantum efﬁciency as a function of the polymer ﬁlm thickness of MEH-CN-PPV on 2nm of gold ͑triangles ͒,MEH-CN-PPV on 3nm of aluminium ͑circles ͒,DHeO-CN-PPV on 2nm of gold ͑ﬁlled squares ͒and of MEH-CN-PPV on 35nm of aluminum ͑open squares ͒.The solid lines are guides to theeye.FIG.5.Normalized PL emission spectra of 15–90-nm-thick MEH-CN-PPV ﬁlms on 3nm of aluminum measured in the inte-gratingsphere.FIG.6.Normalized PL emission spectra of three selected thick-nesses of MEH-CN-PPV ﬁlms on 35nm of aluminum measured in the integrating sphere.189656H.BECKER,S.E.BURNS,AND R.H.FRIENDmirror.19We conclude that nonradiative energy transfer from the excited state of the polymer to the metal efﬁciently quenches luminescence in the proximity of a metalﬁlm,as predicted by the simulations by Chance,Prock,and Silbey.19 However,for three reasons our results are not directly comparable with the calculation of Chance,Prock,and Sil-bey.First,in their model,the quantum efﬁciency of a single dipole at a given distance is calculated.In our experiments the light is emitted over a broad region in the polymerﬁlm depending on where it is absorbed.Even for thick polymer ﬁlms light penetrates far into theﬁlm,where it is absorbed and subsequently emitted in regions close to the metal where it can be quenched.Because of the penetration of light into the polymerﬁlm we expect a reduction in the quantum efﬁ-ciency for relatively thick polymerﬁlms.Second,Chance, Prock,and Silbey,used a model in which the emitter had a quantum yield of unity in free space.It follows that in free space no nonradiative energy decay occurs.Energy transfer to the metal is therefore the only nonradiative decay channel. This means that interference effects do not change the quan-tum efﬁciency for distances where nonradiative energy trans-fer to the metal is negligible.They do,however,alter the quantum efﬁciency at short distances where nonradiative en-ergy transfer to the metal is present.In our structures,shown in Figs.4–6,interference effects alter the PL efﬁciency at all distances when the reﬂectivity of the metalﬁlms is high, since our materials have a free-space quantum efﬁciency around36%,and therefore intrinsic nonradiative decay chan-nels not associated with the metalﬁlm are present.However, interference is negligible for all distances when the reﬂectiv-ity of the metalﬁlms is low.Third,highly transparent metal ﬁlms show a slightly different distance dependence of the nonradiative energy-transfer rate than thick metalﬁlms.At short distances very thinﬁlms quench luminescence more efﬁciently than thick metalﬁlms,whereas for longer dis-tances the opposite is true.182.Polymer on spacer on metal(structure2)We also investigated the PL efﬁciency and the emission spectra of structures where a20-nm-thick polymer layer is separated from the Alﬁlm by a SiO2space ing spacer layers avoids several problems.The emission zone is conﬁned to a thin layer at a given distance to the metal, which gives better spatial resolution and allows better com-parison with simulations for dipoles in front of metal ﬁlms.15,19,24It avoids chemical reactions between the poly-mer and the metal that can alter the emission characteristics of the polymer,e.g.,covalent bonding of Al atoms to the polymer.27It also rules out diffusion of the exciton to the metal as a necessary precondition for quenching.Further-more,no diffusion of metal atoms into the polymer layer͓of the order or3–4nm for Al͑Ref.27͔͒occurs.In addition,a comparison of the EL results with the PL quantum efﬁciency of a polymerﬁlm at various distances to the metal allows us to draw conclusions about the nature of the recombination zone.The measured quantum efﬁciencies were corrected for the absorption of laser light by the Alﬁlm.In Fig.7the PL quantum efﬁciency of a15–20-nm-thick polymerﬁlm separated from2–3-nm-thick Au and Alﬁlms by a transparent SiO2spacer layer is shown as a function of the spacer layer thickness.For a polymerﬁlm spin coated directly onto the metalﬁlm or a5-nm-thick spacer layer,the efﬁciency is reduced from36%in free space to a value be-tween0.06%and3%.We note that contact between the polymerﬁlm and the metal is not necessary for efﬁcient quenching of the PL.The PL quantum efﬁciency increases with increasing SiO2layer thickness.For a separation of ap-proximately60nm,the PL quantum efﬁciency approaches a constant value which is less than the free-space quantum efﬁciency of36%.The excitation density throughout such a thinﬁlm is taken to be approximately constant.For our samples we therefore consider60nm as the distance above which nonradiative energy transfer to the metal becomes negligible.The PL spectra obtained from the polymerﬁlms are shown in Fig.8.As expected,for highly transparent metalﬁlms the shape of the emission spectrum is almost independent of the distance between the polymer layer and the metalﬁlm.Figure9shows the results of the same measurement on samples with a35-nm-thick highly reﬂective Alﬁlm.The FIG.7.PL quantum efﬁciency of a15–20-nm-thick MEH-CN-PPVﬁlm on a SiO2spacer layer on2nm of gold or3nm of aluminum as a function of the SiO2thickness.The solid lines are guides to theeye.FIG.8.Normalized PL emission spectra of15–20-nm-thick MEH-CN-PPVﬁlms separated by SiO2spacer layers of different thicknesses from2nm of gold and3nm of aluminum measured in the integrating sphere.561897EFFECT OF METAL FILMS ON THE...reﬂective and quenching properties of such an Al ﬁlm are identical to that of the bulk.The PL quantum efﬁciency os-cillates as a function of the SiO 2layer thickness.With no spacer layer present,the PL quantum efﬁciency is again re-duced to around 3%.With increasing SiO 2layer thickness the quantum efﬁciency rises to a maximum of 35.5%for a separation of about 75nm between the polymer layer and the metal ﬁlm.For larger distances,the PL is signiﬁcantly re-duced,with the quantum efﬁciency dropping to 5.3%for a SiO 2layer of 210-nm thickness.The PL quantum efﬁciency peaks again,with the quantum efﬁciency reaching 32%,a value slightly lower than that for the ﬁrst peak.We note that the PL quantum efﬁciencies shown in Fig.9have been cal-culated neglecting the absorption of emitted light by the Al.Correction for absorption of PL by the Al would give a maximum PL quantum efﬁciency of 37%,and a minimum PL quantum efﬁciency of 5.6%,as discussed below.The PL spectra from these samples are shown in Fig.10.Interference effects shift the emission peak of a thin MEH-CN-PPV layer on top of a SiO 2spacer and a 35-nm-thick Al ﬁlm over therange of 580–640nm.The emission from a MEH-CN-PPV ﬁlm spin coated onto a glass substrate peaks at 595nm.Discussion .In our experiments we can distinguish be-tween two cases.For very thin metal ﬁlms with low reﬂec-tivities,interference effects are negligible.This is supported by the lack of any dependence of the shape of the emission spectrum on the thickness of the polymer ﬁlm or the SiO 2spacer layer.Nonradiative energy transfer to the metal has,however,been identiﬁed as an efﬁcient decay channel for an emitter in the proximity of a thin metal ﬁlm.19,22The samples with thin metal ﬁlms thus allow us to measure the effect of the metal ﬁlm on the nonradiative energy transfer only and to neglect the effect of interference on the radiative rate.For thick metal ﬁlms we expect both interference effects and energy transfer to the metal to inﬂuence the radiative as well as the nonradiative properties of the light emitter.14,15,19We can identify two different regimes.For short distances ͑below 60nm ͒we see efﬁcient quenching of the lumines-cence for both highly transparent and highly reﬂective metal ﬁlms.We conclude that nonradiative energy transfer to the metal plays an important role in this region.For longer dis-tances the PL efﬁciency remains constant for polymer ﬁlms on thin metal layers but oscillates as a function of distance for highly reﬂective metal ﬁlms.For thicker metal ﬁlms we also observe a signiﬁcant dependence of the shape of the emission spectrum from the distance between the emitter and the metal.We assign these effects to interference between directly emitted waves and waves reﬂected from the metal layer.The effect of interference on the radiative lifetime of an emitting dipole in front of a metal mirror as a function of wavelength and dipole metal separation has been investi-gated in great depth,15,23and,as we discuss below,can ac-count for our observations here.In order to interpret our results,we have analyzed them in terms of the competition between radiative and nonradiative decay processes.The radiative lifetime of an excited mol-ecule oscillates with increasing distance of the molecule from a reﬂective surface.However,when the nonradiative energy transfer to the metal is negligible,the radiative decay channels in a material with a quantum efﬁciency of unity do not compete with any nonradiative decay channels.Changes in the radiative lifetime therefore have no effect on the quan-tum efﬁciency.We note that this is the case for the simula-tions carried out in Ref.19.If,however,nonradiative decay channels are present,as in our materials,an oscillation in the radiative lifetime due to interference effects will allow the nonradiative decay channels to compete more or less favor-ably,depending on whether the radiative lifetime is in-creased or decreased.This leads to an oscillation in quantum efﬁciency.For materials where radiative and intrinsic and extrinsic ͑i.e.,due to the metal ͒nonradiative decay channels compete with each other,we therefore expect a combination of both the effects of interference on the radiative lifetime and of energy transfer to the metal on the nonradiative life-time.At long distances we expect the PL efﬁciency to oscil-late in the same fashion as the radiative lifetime ͑see Fig.9͒.At short distances nonradiative energy transfer will reduce the efﬁciency ͑see Figs.9and 4͒.This effect will be en-hanced by an increase in the radiative lifetime ͑decrease in the radiative rate ͒due to destructiveinterference.FIG.9.Solid circles:PL quantum efﬁciency of a 15–20-nm-thick MEH-CN-PPV ﬁlm on a SiO 2spacer layer on a 35nm of aluminum as a function of the SiO 2thickness.The solid line is a guide to theeye.FIG.10.Normalized PL emission spectra of 15–20-nm-thick MEH-CN-PPV ﬁlms separated by SiO 2spacer layers of four se-lected thicknesses from 35nm of aluminum measured in the inte-grating sphere.189856H.BECKER,S.E.BURNS,AND R.H.FRIEND。

数学宇宙英语演讲稿范文

Ladies and Gentlemen,Good evening. It is my great honor to stand before you today and embark on a journey through the fascinating realm of mathematics, which we often refer to as the language of the universe. Mathematics is not just a subject we study in schools; it is the very fabric that intertwines the cosmos and shapes our understanding of the world around us. Today, I invite you to join me as we explore the wonders of the mathematical universe.The universe itself is a grand work of art, and mathematics is its blueprint. From the smallest subatomic particles to the vast expanse of galaxies, the universe is governed by patterns and structures that can be described and understood through mathematical formulas. Let us delve into the depths of this magnificent universe and discover the role of mathematics in shaping its very essence.I. The Foundations of MathematicsThe journey of mathematics begins with the very foundations upon whichit is built. Mathematics is a discipline that relies on logic, rigor, and precision. It is a language that transcends cultures and languages, and it has been the driving force behind scientific and technological advancements throughout history.1. Numbers: The Universal LanguageNumbers are the building blocks of mathematics. They are the essence of quantity and magnitude, and they have been a part of human existence since the dawn of time. From counting objects to measuring distances, numbers have allowed us to make sense of the world and communicate our understanding of it.2. Arithmetic: The Basic OperationsArithmetic, the study of numbers and their properties, forms the cornerstone of mathematics. The four basic operations—addition, subtraction, multiplication, and division—are the foundation upon which more complex mathematical concepts are built.3. Geometry: The Language of Shape and SpaceGeometry is the branch of mathematics that deals with the properties, relations, and measurements of points, lines, surfaces, and solids. It is the language of shape and space, and it has played a crucial role in understanding the physical world.II. The Mathematical Universe: A Journey Through PatternsThe universe is filled with patterns and regularities that can be discovered and understood through mathematics. Let us explore some of these patterns and their significance.1. The Fibonacci Sequence: Nature's CodeThe Fibonacci sequence, a series of numbers in which each number is the sum of the two preceding ones, is a classic example of a mathematical pattern found in nature. This sequence can be observed in the arrangement of leaves on a plant, the spiral patterns of seashells, and even the branching of trees. The Fibonacci sequence reveals the underlying order and beauty of the natural world.2. The Golden Ratio: The Divine ProportionThe golden ratio, also known as the golden mean, is an irrational number approximately equal to 1.618. It is a ratio that has been found to be aesthetically pleasing and has been used in art, architecture, and nature. The golden ratio can be found in the proportions of the human body, the design of famous buildings like the Parthenon, and even in the Fibonacci sequence.3. Fractals: The Geometry of NatureFractals are complex patterns that are self-similar across different scales. They are found in nature in the form of snowflakes, coastlines, and even the patterns of lightning. Fractals demonstrate the intricate and beautiful structures that can arise from simple mathematical rules.III. Mathematics in the CosmosMathematics plays a crucial role in understanding the cosmos. From the smallest particles to the largest structures, the universe is governed by mathematical laws and principles.1. The Big Bang Theory: Mathematics and the Origin of the UniverseThe Big Bang theory, which describes the origin and evolution of the universe, is based on mathematical equations and observations. The Friedmann equations, which describe the expansion of the universe, are a testament to the power of mathematics in unraveling the mysteries of the cosmos.2. General Relativity: The Geometry of Space-TimeAlbert Einstein's theory of general relativity, which describes gravity as the curvature of space-time, is a profound example of how mathematics can be used to understand the fundamental forces that govern the universe.3. Quantum Mechanics: The Mathematics of the MicrocosmQuantum mechanics, the branch of physics that deals with the behavior of matter and energy at the smallest scales, relies heavily on mathematics. The Schrödinger equation, which describes the behavior of quantum particles, is a complex mathematical expression that has revolutionized our understanding of the universe.IV. The Impact of Mathematics on SocietyMathematics has had a profound impact on society, shaping the way welive and work. From the development of technology to the advancement of medicine, mathematics has been a driving force behind human progress.1. Technology: The Pillar of Modern SocietyTechnology has become an integral part of our lives, and mathematics is the backbone of its development. From computers to smartphones, from the internet to artificial intelligence, mathematics has enabled the creation of countless technological marvels that have transformed the world.2. Medicine: Healing Through NumbersMedicine, one of the most critical fields of human endeavor, has been revolutionized by mathematics. Mathematical models and algorithms are used to predict disease outbreaks, analyze genetic information, and develop new drugs and treatments.V. ConclusionIn conclusion, the mathematical universe is a wondrous and intricate tapestry of patterns and structures that governs the cosmos. Mathematics is not just a subject to be studied; it is the very language that describes the universe and its wonders. As we journey through the mathematical universe, we come to appreciate the beauty and elegance of numbers, shapes, and patterns that shape our world.Ladies and gentlemen, let us embrace the power of mathematics and continue to explore the mysteries of the universe. For in the words of the great mathematician Pythagoras, "All is number." Thank you.。

林分密度对观赏型南方红豆杉幼树生长及形态可塑性的影响

林分密度对观赏型南方红豆杉幼树生长及形态可塑性的影响欧建德【摘要】通过调查测定福建明溪县不同密度观赏型南方红豆杉人工林幼树的生长指标和形态指标，研究其生长及形态学特征与林分密度的关系。

结果表明，不同密度林分的幼树在冠长、冠幅、地径、枝下高、侧枝数量等树冠特征性状和圆满度、枝叶浓密度等观赏性状方面均存在显著差异，在树高及叶色间不存在显著差异。

林分密度对生物量的分布格局有着显著影响，对不同器官生物量、生物量分配比等指标均有显著影响；单株不同器官生物量和叶枝干等器官生物量分配比，根生物量分配比和地上/地下生物量比均随林分密度增加而降低。

林分密度对1级侧枝分枝角、1级侧枝数量、1级侧枝密度及平均长度有着显著影响，且随着林分密度增加而下降，幼树树冠对林分密度有着显著可塑性响应，表现出强烈的可塑性反应。

%The growth and morphological characteristics of ornamental type Taxus chinensis var.mairei saplings in plantations with different stand densities were studies by sampling measurements in Mingxi County,Fujian.The results showed that there were significant differences in crown length crown diameter,basal diameter,the lowest branch height, number of lateral branches,the vertical distribution of leaf area,ratio of crown diameter and crown length (CFR),the dense foliage of the plant among the ornamental Taxus chinensis var.mairei plantations with different stand densities. There were no significant differences in tree height,leaf color under different stand structures.The biomass distribution pattern,different organ biomass,biomass allocation ratio,above and below ground biomass ratio of the saplings was all significantly correlated with the stand structuredensity.The average biomass of different organs per sapling,the biomass allocation ratio in the leaves,branches and the stem of each sapling,the root biomass allocation ratio,and the ratio of aboveground biomass/underground biomass were all decreased along with the increase of stand density.The stand den-sity played a significantly important role in controlling the first-order branching angle,the number of first-order lateral branches,the average length of first-order lateral branches,the density of first-order lateral branches,and all these in-dexes were also decreased along with the increase of the stand density,expressing the growth strategy of the highly dense stand structure that the differentiation of first-order branches was strongly inhibited to promote the stem growth.The crown structure of the saplings significantly responded to the stand density and demonstrated a strong plasticity.【期刊名称】《西南林业大学学报》【年(卷),期】2014(000)005【总页数】6页(P31-36)【关键词】南方红豆杉;林分密度;生物量分配;形态可塑性;明溪县【作者】欧建德【作者单位】明溪县林业局，福建明溪365200【正文语种】中文【中图分类】S718.42南方红豆杉(Taxus chinensis var.mairei Cheng et L.K)是我国南方重要的药用、材用和观赏树种，随着人们对其认识的提高，该树种已广泛应用于园林绿化方面，其产业规模也不断扩大，已成为我国的重要园林绿化树种[1]。

Body Sensor

Body SensorMeasure body motionLibrarySensors & ActuatorsDescriptionThe Body Sensor block senses the motion of a body represented by a Body block. You connect the Body Sensor to a Body coordinate system (CS) on the Body whose motion you want to sense. The sensor specifically measures the motion of the origin of this Body CS.The Body Sensor measures the components of translational and rotational motion in any combination of:Translational position, velocity, and acceleration vectors. The position vector has its tail at the World CS origin.Rotational orientation (a 3-by-3 rotation matrix R) and angular velocity and acceleration vectorsIn the block dialog, you choose the reference coordinate system (CS) axes in which these components are represented.The input is the connector port connected to the Body being sensed. The outport is a set of Simulink signals or one bundled Simulink signal of the selected matrix and/or vector components.Coordinate Representations and Body OrientationA body's orientation rotation matrix R relates the components of the same vector v as measured in the inertial World CS and in the Body CS by v b = R T·v W. The column vector v W lists the vector v's three components measured in the World CS. The column vector v b lists the vector v's three components measured in the Body CS.The columns of the rotation matrix R are the components of the Body CS unit basis vectors measured with respect to the World axes.See Representations of Body Motion and Representations of Body Orientation in the "Representing Motion" chapter for more details on representing body position and orientation, rotation matrices, and angular velocity. Body Position-Orientation and the Home ConfigurationThe Body Sensor block can measure the position and/or orientation of a body. It measures these relative to the home configuration of the machine, the machine state before the application of initial condition actuators and assembly of disassembled joints. Thus the Body Sensor includes the effect of the latter, which act before the simulation starts.Dialog Box and ParametersThe dialog has one active area, Measurements .Measurements Select the check box for each of the possible measurements you want to make:Translational motion: Position , Velocity , and Acceleration vectors: r , v = d r /dt, and a = d v /dt, respectively.Rotational motion: Angular velocity and Angular acceleration vectors and Rotation matrix :The Rotation matrix is the 3-by-3 orthogonal rotation matrix R :representing rotational orientation and satisfying R T R = RR T= I . The components are output columnwise as a 9-component row vector: (R 11, R 21, R 31, R 12, ... ).With respect to CSIn the pull-down menu, choose the coordinate system in which the body motion components arerepresented: either the Local (Body CS) to which the Sensor is connected or the default Absolute (World).In the Absolute case, the rotation matrix R and the motion vectors have components represented in the inertial World CS axes. In the Local case, the same body motion components are premultiplied by thebody's inverse orientation rotation matrix R -1 = R T .Each vector measurement is a row vector in the Simulink output signal. The selected signals are ordered inthe same sequence as the dialog.If you choose the With respect to coordinate system as Absolute (World), the Rotation matrix measures the body's rotational orientation with respect to the World CS. Recall the relationship of vector components in the World and body coordinate axes, v W = R·v b.If you choose the With respect to coordinate system as Local (Body CS), the Rotation matrix returns the 3-by-3 identity matrix R T R = I.The angular velocity is ωj = (1/2)ΣikɛijkΩik , where the matrix Ω = +(d R/dt)*R T = -R*(dR T/dt), and ɛis the permutation symbol. The angular acceleration is α = dω/dt.In the Units pull-down menus, choose the units for each of the measurements you want: Translation: the defaults are m (meters), m/s (meters/second), and m/s2 (meters/second2), respectively, for Position, Velocity, and Acceleration.Rotation: the defaults are deg/s (degrees/second) and deg/s2 (degrees/second2), respectively, for Angular velocity and Angular acceleration. The Rotation matrix is dimensionless.Output selected parameters as one signalSelect this check box to convert the output signals into a single bundled signal. The default is selected. If you clear it, the Body Sensor block will grow as many Simulink outports as there are active signalsselected, one port for each selected signal.If the check box is selected, the Simulink signal out has all the active (selected) signals ordered into a single row vector, in the same order you see in the dialog. Nonselected components are removed from the vector signal.The sensor outputs are ordered and labeled as follows.Here is a Body Sensor connected to a Body:You must connect the Body Sensor to the Body at one of its Body CS ports. The Sensor measures the motion of that Body CS.See AlsoBody, Body Actuator, Constraint & Driver Sensor, Joint Sensor, Mechanical Branching BarSee Kinematics and Machine Motion State, Representations of Body Motion, and Representations of Body Orientation for more details on representing body position and orientation.See Sensing Motions and Forces.See the relevant entries in the Glossary about body orientation: axis-angle rotation, Euler angles, right-hand rule, and rotation matrix.In Simulink, see the Signal Routing Library and the Sinks Library.© 1984-2011-The MathWorks, Inc. -Site Help-Patents-Trademarks-Privacy Policy-PreventingPiracy-RSS。

测量设备管理程序

测量设备管理程序Procedure for Management of Measuring Equipment1. 目的 PURPOSE在整个生命周期中对测量设备进行管理，以确保需要时能获得适宜的测量设备。

To manage the measuring equipment throughout the whole lifecycle, to ensure suitable measuring equipment can be obtained when needed.2. 范围 SCOPE2.1. 仅适用于与品质有关的测量设备Is only applied to quality related measuring equipments2.2. 除6.6章节“测量系统分析（MSA）”外，其他均为通用要求The others are general requirement except Section 6.6 “Measurement SystemAnalysis (MSA)”3. 定义 DEFINITION3.1. 测量设备：本文中指用于确定量值的设备和（或）装置的统称。

放大镜、物理显微镜、CCD、摇摆测试机等不属测量设备，因为它不确定量值；通止规虽然只能判断合格与不合格，但带有尺寸属性，因此属于测量设备。

Measuring equipment: In this document, it is the combination of equipments and(or) devices which assign numbers or values. Magnifiers, physical microscope,CCD, vibration tester are not measuring equipment, because they do not assignnumbers or values; even Go/No Go gage only judges pass or reject, but it isdimensional, so it is measuring equipment.3.2. 测量系统：测量或者评估过程中所使用的测量或监视设备、测量标准、操作、方法、夹具、软件、人员、环境和假设的整体。

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a r X i v :h e p -e x /0605103v 1 24 M a y 2006EPJ manuscript No.(will be inserted by the editor)Measurements of the absolute branching fractionsfor D →K ∗e +νe and determination ofΓ(D +→K 0e +νe )(BES Collaboration)M.Ablikim 1,J.Z.Bai 1,Y.Ban 12,J.G.Bian 1,X.Cai 1,H.F.Chen 16,H.S.Chen 1,H.X.Chen 1,J.C.Chen 1,Jin Chen 1,Y.B.Chen 1,S.P.Chi 2,Y.P.Chu 1,X.Z.Cui 1,Y.S.Dai 18,L.Y.Diao 9,Z.Y.Deng 1,Q.F.Dong 15,S.X.Du 1,J.Fang 1,S.S.Fang 2,C.D.Fu 1,C.S.Gao 1,Y.N.Gao 15,S.D.Gu 1,Y.T.Gu 4,Y.N.Guo 1,Y.Q.Guo 1,K.L.He 1,M.He 13,Y.K.Heng 1,H.M.Hu 1,T.Hu 1,G.S.Huang 1a ,X.T.Huang 13,X.B.Ji 1,X.S.Jiang 1,X.Y.Jiang 5,J.B.Jiao 13,D.P.Jin 1,S.Jin 1,Yi Jin 8,i 1,G.Li 2,H.B.Li 1,H.H.Li 1,J.Li 1,R.Y.Li 1,S.M.Li 1,W.D.Li 1,W.G.Li 1,X.L.Li 1,X.N.Li 1,X.Q.Li 11,Y.L.Li 4,Y.F.Liang 14,H.B.Liao 1,B.J.Liu 1,C.X.Liu 1,F.Liu 6,Fang Liu 1,H.H.Liu 1,H.M.Liu 1,J.Liu 12,J.B.Liu 1,J.P.Liu 17,Q.Liu 1,R.G.Liu 1,Z.A.Liu 1,Y.C.Lou 5,F.Lu 1,G.R.Lu 5,J.G.Lu 1,C.L.Luo 10,F.C.Ma 9,H.L.Ma 1,L.L.Ma 1,Q.M.Ma 1,X.B.Ma 5,Z.P.Mao 1,X.H.Mo 1,J.Nie 1,H.P.Peng 16d ,R.G.Ping 1,N.D.Qi 1,H.Qin 1,J.F.Qiu 1,Z.Y.Ren 1,G.Rong 1,L.Y.Shan 1,L.Shang 1,C.P.Shen 1,D.L.Shen 1,X.Y.Shen 1,H.Y.Sheng 1,H.S.Sun 1,J.F.Sun 1,S.S.Sun 1,Y.Z.Sun 1,Z.J.Sun 1,Z.Q.Tan 4,X.Tang 1,G.L.Tong 1,D.Y.Wang 1,L.Wang 1,L.L.Wang 1,L.S.Wang 1,M.Wang 1,P.Wang 1,P.L.Wang 1,W.F.Wang 1b ,Y.F.Wang 1,Z.Wang 1,Z.Y.Wang 1,Zhe Wang 1,Zheng Wang 2,C.L.Wei 1,D.H.Wei 1,N.Wu 1,X.M.Xia 1,X.X.Xie 1,G.F.Xu 1,X.P.Xu 6,Y.Xu 11,M.L.Yan 16,H.X.Yang 1,Y.X.Yang 3,M.H.Ye 2,Y.X.Ye 16,Z.Y.Yi 1,G.W.Yu 1,C.Z.Yuan 1,J.M.Yuan 1,Y.Yuan 1,S.L.Zang 1,Y.Zeng 7,Yu Zeng 1,B.X.Zhang 1,B.Y.Zhang 1,C.C.Zhang 1,D.H.Zhang 1,H.Q.Zhang 1,H.Y.Zhang 1,J.W.Zhang 1,J.Y.Zhang 1,S.H.Zhang 1,X.M.Zhang 1,X.Y.Zhang 13,Yiyun Zhang 14,Z.P.Zhang 16,D.X.Zhao 1,J.W.Zhao 1,M.G.Zhao 1,P.P.Zhao 1,W.R.Zhao 1,Z.G.Zhao 1c ,H.Q.Zheng 12,J.P.Zheng 1,Z.P.Zheng 1,L.Zhou 1,N.F.Zhou 1c ,K.J.Zhu 1,Q.M.Zhu 1,Y.C.Zhu 1,Y.S.Zhu 1,Yingchun Zhu 1d ,Z.A.Zhu 1,B.A.Zhuang 1,X.A.Zhuang 1,B.S.Zou 11Institute of High Energy Physics,Beijing 100049,People’s Republic of China2China Center for Advanced Science and Technology(CCAST),Beijing 100080,People’s Republic of China 3Guangxi Normal University,Guilin 541004,People’s Republic of China 4Guangxi University,Nanning 530004,People’s Republic of China 5Henan Normal University,Xinxiang 453002,People’s Republic of China 6Huazhong Normal University,Wuhan 430079,People’s Republic of China 7Hunan University,Changsha 410082,People’s Republic of China 8Jinan University,Jinan 250022,People’s Republic of China 9Liaoning University,Shenyang 110036,People’s Republic of China 10Nanjing Normal University,Nanjing 210097,People’s Republic of China 11Nankai University,Tianjin 300071,People’s Republic of China 12Peking University,Beijing 100871,People’s Republic of China 13Shandong University,Jinan 250100,People’s Republic of China 14Sichuan University,Chengdu 610064,People’s Republic of China 15Tsinghua University,Beijing 100084,People’s Republic of China 16University of Science and Technology of China,Hefei 230026,People’s Republic of China 17Wuhan University,Wuhan 430072,People’s Republic of China 18Zhejiang University,Hangzhou 310028,People’s Republic of Chinaa Current address:Purdue University,West Lafayette,IN 47907,USAb Current address:Laboratoire de l’Acc´e l´e rateur Lin´e aire,Orsay,F-91898,Francec Current address:University of Michigan,Ann Arbor,MI 48109,USAd Current address:DESY,D-22607,Hamburg,GermanyReceived:date /Revised version:dateing the data of about 33pb −1collected at and around 3.773GeV with the BES-II detector at the BEPC collider,we have studied the exclusive semileptonic decays D +→K −π+e +νe ,D 0→K ∗0e +νe and D 0→K ∗−e +νe .The absolute branching fractions for the decays are measured tobe BF (D +→K −π+e +νe )=(3.50±0.75±0.27)%,BF (D 0→2Please give a shorter version with:\authorrunning and \titlerunning prior to \maketitle1IntroductionSemileptonic decays oﬀer access to weak interaction matrix elements since the eﬀects of weak and strong inter-actions can be separated reasonable well.Measurements of branching fractions for exclusive decays of D mesons play an important role to develop and to test models of their decay mechanisms.Earlier theoretical predictions [1][2]impliedthatthe ratioofthe vectorto pseudoscalar D meson semileptonicdecay rates R =Γ(D →Ke +νe )lies in the range from 0.9to 1.2[3].E691Collaboration reported a measurement with a lower ratio Γ(D +→Kπe +νe )/Γ(D →K 0π−e +νe ,D +→1+p 2(p in GeV/c )and dE/dxresolution of 8.5%for Bhabha scattering electrons are ob-tained for the data taken at√E (E in GeV)and spatial resolutions of σφ=7.9mrad and σZ =2.3cm for electrons.A solenoidal magnet outside the BSC provides a 0.4T magnetic ﬁeld in the central tracking region of the detector.Three double-layer muoncounters instrument the magnet ﬂux return and serve to identify muons with momentum greater than 500MeV/c.They cover 68%of the total solid angle.3Data analysisThe ψ(3770)resonance is produced in electron-positron (e +e −)annihilation at the center-of-mass energy of about 3.773GeV.It is believed to decay predominately intoD 0¯D0and D +D −pairs.Therefore,if a ¯D meson is fully reconstructed (this is called a singly tagged ¯Dmeson)[8][9],the D meson must exist in the system recoiling against thesingly tagged ¯Dmeson.In the system recoiling against singly tagged D −and ¯D0mesons,we select semileptonic decays D +→K −π+(K 0π−(K ∗−)e +νe respectively,and measure branching fractions for the de-cays directly.3.1Event selectionIn order to ensure the well-measured 3-momentum vectors and the reliability of the charged-particle identi-ﬁcation,all charged tracks are required to be well recon-structed in the MDC with good helix ﬁts,and to satisfy a geometry cut |cos θ|<0.85,where θis the polar an-gle.Each track,except for those from K 0S decays,must originate from the interaction region,which is deﬁned by V xy <2.0cm and |V z |<20.0cm,where V xy and |V z |are the closest approach of the charged track in the xy -plane and z direction.Pions and kaons are identiﬁed using the dE/dx and TOF measurements,with which the combined conﬁdence levels (CL πor CL K )for a pion or kaon hypotheses are calculated.A pion candidate is required to have CL π>0.001.In order to reduce misidentiﬁcation,a kaon can-didate is required to satisfy CL K >CL π.Electrons are identiﬁed using the dE/dx ,TOF and BSC measurements,with which the combined conﬁdence level (CL e )for the electron hypotheses is calculated.An electron candidate is required to have CL e >0.001and satisfy the relation CL e /(CL e +CL K +CL π)>0.8.Neutral kaons are reconstructed through the decay K 0S →π+π−.The diﬀerence between the invariant massof π+π−combinations and the K 0S nominal mass shouldbe less than 20MeV/c 2.Neutral pions are reconstructed through the decay π0→γγ.A good photon candidate must satisfy the fol-lowing criteria:(1)the energy deposited in the BSC is greater than 70MeV;(2)the electromagnetic shower starts in the ﬁrst 5readout layers;(3)the angle between the pho-ton and the nearest charged track is greater than 22◦;(4)the opening angle between the direction of the cluster de-velopment and the direction of the photon emission is less than 37◦.Please give a shorter version with:\authorrunning and \titlerunning prior to \maketitle 3250500050010200500500100010*******1001.802 1.832 1.862 1.89210001.802 1.832 1.862 1.892Invariant Mass(GeV/c 2)E v e n t s /(0.001G e V /c 2)(a)(b)(c)(d)(e)(f)(g)(h)(i)(j)Fig.1.The distributions of the ﬁtted invariant masses of the nKmπ(n =0,1,2;m =1,2,3,4)combinations in the singly tagged D −modes:(a)K +π−π−,(b)K 0π−,(c)K 0K −,(d)K +K −π−,(e)K 0π−π−π+,(f)K 0π−π0,(g)K +π−π−π0,(h)K +π−π−π−π+,(i)π−π−π+and (j)sum of the nine modes.020040002004000100200400 1.82 1.84 1.86 1.88Invariant Mass(GeV/c 2)E v e n t s /(0.001G e V /c 2)(a)(b)(c)(d)Fig. 2.The distributions of the ﬁtted invariant masses of the Kmπ(m =1,2,3)combinations in the singly tagged ¯D0modes:(a)K +π−,(b)K +π−π−π+,(c)K 0π+π−and (d)K +π−π0.3.2Singly tagged D −and ¯D0samples The singly tagged D −and ¯D0samples used in this anal-ysis were selected in the previous work [8][9],we here give a brief description for the selection of the singly taggedD −and ¯D0samples.The singly tagged D −mesons are reconstructed in nine hadronic decay modes of K +π−π−,K 0π−,K 0K −,K +K −π−,K 0π−π−π+,K 0π−π0,K +π−π−π0,K +π−π−π−π+and π−π−π+.And the singly tagged ¯D0mesons are reconstructed in four hadronic decay modes of K +π−,K +π−π−π+,K 0π+π−and K +π−π0.In order to improve the momentum resolution and the ratio of signal to combinatorial background in the invari-ant mass spectra,the center-of-mass energy constraint kinematic ﬁt is imposed on each of the nKmπ(n =0,1,2;m =1,2,3,4)combinations.If there is a K 0S or π0among the D daughter particles,an additional constraint kine-matic ﬁt will be imposed on the decay K 0S →π+π−or π0→γγ.Combinations with a kinematic ﬁt probability greater than 0.1%are accepted.If more than one combina-tion satisﬁes the criteria in an event,only the combination with the largest ﬁt probability is retained.The resulting distributions of the ﬁtted invariant masses of the nKmπcombinations,which are calculated using the ﬁtted momentum vectors from the kinematic ﬁt,areshown in Fig.1and Fig.2for the singly tagged D −and ¯D0modes,respectively.A maximum likelihood ﬁt to the massspectrum with a Gaussian function for the ¯Dsignal and a special function [8][9]to describe the background shape yields the observed numbers of the singly tagged D −and ¯D0mesons for each mode.These give the total number of the reconstructed singly tagged ¯Dmesons,5321±149±160for D −[8]and 7584±198±341for ¯D0[9],where the ﬁrst error is statistical and the second systematic obtained by varying the parameterization of the background.3.3Candidates for D +→K −π+e +νe and D 0→K 0π−e +νe are selected from the survivingtracks in the system recoiling against the singly tagged ¯Dmesons.For the selected candidate events,it is required that there should be no extra charged track or isolated photon,which has not been used in the reconstructionof the singly tagged ¯Dmesons.The isolated photon de-tected in the BSC should have an energy exceeding 100MeV and should satisfy the photon selection criteria de-scribed earlier.There are possible hadronic backgrounds for each semileptonic decay due to misidentiﬁcation of a charged pion as an electron,for example,the decay D +→K −π+π+(D 0→K 0π−e +νe ).However,theseevents can be suppressed by requiring the invariant masses of K −π+e +(4Please give a shorter version with:\authorrunning and \titlerunning prior to \maketitle100001000500100-0.4-0.3-0.2-0.100.10.20.30.4U miss (GeV)E v e n t s /(0.01G e V )(a)(b)(c)(d)Fig.3.The distributions of the U miss for the Monte Carlo events of (a)D +→K −π+e +νe versus D −→K +π−π−,(b)D +→K −π+e +νe versus D −→K +π−π−π0,(c)D 0→K 0π−e +νeversus ¯D0→K +π−π0.0510123-0.4-0.3-0.2-0.10.10.20.30.4U miss (GeV)E v e n t s /(0.02G e V )(a)(b)Fig.4.The distributions of the U miss for the selected can-didates for (a)D +→K −π+e +νe and (b)D 0→K 0π−e +νe are observedin the system recoiling against the singly tagged ¯D.3σU miss,i ,where the σU miss,i is the standard deviation ofthe U miss,i distribution obtained by analyzing the Monte Carlo events of D +→K −π+e +νe (D 0→K 0π−e +νe versus ¯D0→K +π−and D 0→K 0π−e +νe from the data.Figure 5shows the distributions of the ﬁtted invari-ant masses of the nKmπcombinations from the events in which the candidates for D +→K −π+e +νe and D 0→K 0π−e +νe .There may also be theπ+π−combinatorial background.By selecting the events in whichtheinvariant masses of the π+π−combinationson the recoil side of the tags are outside of the K 0S massPlease give a shorter version with:\authorrunning and \titlerunning prior to \maketitle 5024680240.70.80.911.11.2Invariant Mass(GeV/c 2)E v e n t s /(0.02G e V /c 2)(a)(b)Fig.6.The distributions of the invariant masses of (a)K −π+combinations from the selected candidates for D +→K 0π−combinations from the selected candidates forD 0→K ∗−e +νe .window,we estimate that there are 0.6±0.2background events in the candidate events.After subtracting the num-ber of background events,9.3±3.4candidate events are retained.3.4Candidates for D +→K ∗0e +νe andD 0→K ∗−e +νe ,we calculate the invariant masses of K −π+(K 0π−e +νe ).Fig.6(a)andFig.6(b)show the distributions of the invariant masses of K −π+andK ∗0signal is observed in Fig.6(a).Fit-ting the K −π+invariant mass spectrum with a Gaussian function for theK ∗0e +νe .In the ﬁt,the mass and width ofK 0π−invari-ant mass spectrum in Fig.6(b)yields 7.4±3.3candi-dates for D 0→K ∗−e +νe .After subtracting the number of π+π−combinatorial background of 0.1±0.1events,7.3±3.3candidate events are retained.2468Momentum of electron(GeV/c)E v e n t s /(0.1G e V /c )Fig.7.The distribution of the momentum of the electrons from the selected candidates for D +→K ∗0e +νe .However,there are still some K ∗contaminations from other modes of D meson decays or from continuum back-ground due to the combinatorial background in the singlytagged ¯Dsignal regions.These K ∗contaminations must be subtracted from the ﬁtted number of the selected can-didates for D +→K ∗0e +νe andD 0→K ∗−e +νe are obtained respectively.After subtract-ing the numbers of the background events,28.3±6.6and 6.6±3.3candidate events for D +→K ∗0e +νe is shownin Fig.7,where the points with error bars are from the data and the histogram is from the Monte Carlo events of D +→6Please give a shorter version with:\authorrunning and \titlerunning prior to \maketitleby analyzing the Monte Carlo sample which is about 14times larger than the data.The Monte Carlo events aregenerated as e +e −→D ¯D,where the D and ¯D mesons are set to decay into all possible ﬁnal stateswith the branch-ing fractions quoted from PDG [11]excluding the decay modes under study.The particle trajectories are simulated with the GEANT3based Monte Carlo simulation package for the BES-II detector [12].The number of the events sat-isfying the selection criteria is then normalized to the data.Monte Carlo study shows that the dominant backgroundfor D +→K −π+(K ∗0µ+νµ,and the background for D 0→K 0π−e +νe ,D +→K 0π−e +νe ,D +→K 0π−e +νe ,D +→K 0π−e +νe=(4.30±0.05)%,ǫD +→K 0π−e +νe ,N ¯D tag ×ǫD →j,(1)where N D →j is the number of the signal events for the j thmode;N ¯D tag is the total number of the singly tagged D −or ¯D0mesons;ǫD →j is the detection eﬃciency for the j th mode.Inserting these numbers in Eq.(1),we obtain the branching fractions for the semileptonic decays to beBF (D +→K −π+e +νe )=(3.50±0.75±0.27)%,BF (D 0→K ∗0e +νe )=(5.06±1.21±0.40)%andBF (D 0→K ∗−e +νe )=(2.87±1.48±0.39)%,where the ﬁrst error is statistical and the second sys-tematic.The systematic error arises mainly from the un-certainties in tracking eﬃciency (∼2.0%per track),in particle identiﬁcation (∼0.5%per track for charged pion or kaon,∼1.0%per track for electron),in photon selec-tion (∼2.0%),in K 0Sselection (∼1.1%),in U miss selec-tion (∼0.6%),in background subtraction [∼(2.5%∼9.3%)],in Monte Carlo statistics [∼(0.8%∼1.4%)],in the num-ber of the singly tagged ¯Dmesons (∼3.0%for D −and ∼4.5%for ¯D0)and in the ﬁt to the mass spectrum of K −π+orK ∗0e +νe and ∼2.5%for D 0→K ∗−e +νe ).These uncertainties are added in quadrature to obtain the total systematic er-ror,yielding ∼7.6%,∼10.8%,∼8.0%and ∼13.7%for the semileptonic decays D +→K −π+e +νe ,D 0→K ∗0e +νe and D 0→K ∗−e +νe ,respectively.4.3The ratio ofΓ(D +→Γ(D +→K ∗0e +νe and the previously measured branching fraction BF (D +→K ∗0e +νe )K 0e +νe )=0.57±0.17±0.02,where the ﬁrst error is statistical and the second system-atic which arises mainly from the uncanceled systematicuncertainties including K 0S selection (∼1.1%),background subtraction (∼3.5%),Monte Carlo statistics (∼1.1%)and the ﬁt to the mass spectrum of K −π+combinations (∼1.7%).5SummaryUsing the data of about 33pb −1collected around 3.773GeV with the BES-II detector at the BEPC collider,the absolute branching fractions for the decays D +→K −π+e +νe ,D 0→K ∗0e +νe and D 0→K ∗−e +νe are measured to be BF (D +→K −π+e +νe )=(3.50±0.75±0.27)%,BF (D 0→K ∗0e +νe )=(5.06±1.21±0.40)%and BF (D 0→K ∗−e +νe )=(2.87±1.48±0.39)%.With the measured branching fraction for D +→K 0e +νe ,the ratio of the vector to pseudoscalar D meson semileptonic decay rates Γ(D +→K 0e +νe )is determined to be 0.57±0.17±0.02,which is in good agreement with theoretical predictions and other measurements [6][7]within error.Please give a shorter version with:\authorrunning and\titlerunning prior to\maketitle7 6AcknowledgmentThe BES collaboration thanks the staﬀof BEPC andcomputing center for their hard eﬀorts.This work is sup-ported in part by the National Natural Science Founda-tion of China under contracts Nos.10491300,10225524,10225525,10425523,the Chinese Academy of Sciences un-der contract No.KJ95T-03,the100Talents Programof CAS under Contract Nos.U-11,U-24,U-25,and theKnowledge Innovation Project of CAS under ContractNos.U-602,U-34(IHEP),the National Natural ScienceFoundation of China under Contract No.10225522(Ts-inghua University).References1.M.Wirbel,B.Stech and M.Baucer,Z.Phys.C29(1985)637.2.V.Lubicz et.al,Phys.Lett.B274(1992)415.3.J.D.Richman and P.R.Burchat,Rev.Mod.Phys.67(1995)893.4.The Tagged Photon Spectrometer Collaboration,J.C.Anjoset al.,Phys.Rev.Lett.62(1989)722.5.Mark III Collaboration,Z.Bai et al.,Phys.Rev.Lett.66(1991)1011.6.FOCUS Collaboration,J.M.Link et al.,Phys.Lett.B598(2004)33.7.CLEO Collaboration,G.S.Huang et al.,Phys.Rev.Lett.95(2005)181801.8.BES Collaboration,M.Ablikim,et al.,Phys.Lett.B608(2005)24.9.BES Collaboration,M.Ablikim,et al.,Phys.Lett.B597(2004)39.10.BES Collaboration,J.Z.Bai et al.,Nucl.Instrum.MethodsA458(2001)627.11.S.Eidelman et al.(Particle Data Group),Phys.Lett.B592(2004)1.12.BES Collaboration,M.Ablikim,et al.,Nucl.Instrum.Methods A552(2005)344.。