Overview of Physics at a Muon Collider

合集下载

Quantum Mechanics

Quantum MechanicsQuantum mechanics is a branch of physics that deals with the behavior of matter and energy at a microscopic level. It is a fundamental theory that explains how the universe works at its most basic level. Quantum mechanics is a complex and fascinating field that has revolutionized our understanding of the universe. In this essay, I will explore the basics of quantum mechanics, its implications, and the challenges it presents.At the heart of quantum mechanics is the concept of the wave-particle duality. This means that particles, such as electrons and photons, can behave as both waves and particles. This is a fundamental departure from classical physics, which assumes that particles are always particles and waves are always waves. The wave-particle duality is a key aspect of quantum mechanics and is essential to understanding its many applications.One of the most famous applications of quantum mechanics is in the field of quantum computing. Quantum computers use the properties of quantum mechanics to perform calculations that are impossible for classical computers. This is because quantum computers can perform multiple calculations simultaneously, whereas classical computers can only perform one calculation at a time. Quantum computers have the potential to revolutionize fields such as cryptography, drug discovery, and artificial intelligence.Another important aspect of quantum mechanics is quantum entanglement. This is a phenomenon where two particles become entangled and share a quantum state. When this happens, any change to one particle will instantly affect the other particle, no matter how far apart they are. This has important implications for the field of quantum communication, where information can be transmitted using entangled particles. Quantum entanglement also has implications for the nature of reality, as it challenges our classical understanding of causality and locality.Despite its many applications, quantum mechanics presents many challenges. One of the biggest challenges is the measurement problem. In quantum mechanics, particles exist in a state of superposition, where they can exist in multiple states simultaneously. However, when a measurement is taken, the particle collapses into a single state. This presents a paradox, as it is unclear whatcauses the collapse of the wave function. This has led to many interpretations of quantum mechanics, such as the Copenhagen interpretation, the many-worlds interpretation, and the pilot wave theory.Another challenge presented by quantum mechanics is the problem of decoherence. Decoherence is the process by which a quantum system interacts with its environment, causing it to lose its quantum properties. This makes it difficult to maintain a quantum state for any length of time, which is a major obstacle for the development of practical quantum technologies.In conclusion, quantum mechanics is a fascinating and complex field that has revolutionized our understanding of the universe. It is a fundamental theory that has many applications, from quantum computing to quantum communication. However,it also presents many challenges, such as the measurement problem and the problem of decoherence. Despite these challenges, quantum mechanics is a field that is constantly evolving, and it will continue to shape our understanding of the universe for many years to come.。

海底两万里中物理学的句子

海底两万里中物理学的句子英文回答：Physics plays a significant role in Jules Verne's novel "Twenty Thousand Leagues Under the Sea." As the story follows the adventures of Professor Aronnax, Ned Land, and Conseil aboard the Nautilus, many instances highlight the application of physics principles.One example is the concept of buoyancy. The Nautilus, being a submarine, must maintain neutral buoyancy to navigate underwater. This is achieved by adjusting the amount of water in the ballast tanks. By controlling the density of the Nautilus, Captain Nemo ensures that the upward force exerted by the water equals the downward force of the submarine, allowing it to float at a desired depth. This demonstrates Archimedes' principle, which states that an object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces.Another physics concept explored in the novel is pressure. As the Nautilus dives deeper into the ocean, the pressure increases significantly. The characters experience this firsthand when they descend to great depths and feel the pressure on their bodies. This aligns with Pascal's principle, which states that pressure is transmitted uniformly in all directions in a fluid. The immense pressure at great depths is a result of the weight of the water above pressing down on the submarine.Furthermore, the novel touches upon the principles of electricity and magnetism. The Nautilus is powered by electricity, and Verne describes the use of electric motors to propel the submarine through the water. The concept of electromagnetism is also evident in the use of magnetic fields to navigate and detect underwater objects. These applications of physics showcase the integration of scientific knowledge into the fictional world of the Nautilus.中文回答：物理学在朱尔·凡尔纳的小说《海底两万里》中起着重要的作用。

20世纪物理学英文版

20世纪物理学英文版The 20th century witnessed significant advancements in the field of physics. Many groundbreaking discoveries and theories emerged during this time, shaping our understanding of the fundamental laws that govern the universe. In this response, I will provide a comprehensive overview of the major developments in physics during the20th century, focusing on key theories, experiments, and notable physicists.One of the most revolutionary theories in physics during the 20th century is Albert Einstein's theory of relativity. Einstein's special theory of relativity, published in 1905, introduced the concept that the laws of physics are the same for all observers moving at a constant speed relative to each other. It also proposed that the speed of light is constant and that time, space, and mass are relative to the observer's frame of reference. Later, in 1915, Einstein developed the general theory of relativity, which provided a new understanding of gravityby describing it as the curvature of spacetime caused by massive objects.Quantum mechanics, another groundbreaking theory, emerged in the early 20th century. It revolutionized our understanding of the behavior of particles at the atomic and subatomic levels. Max Planck's work on black-body radiation in 1900 laid the foundation for quantum theory. Later, in 1925, Werner Heisenberg formulated the uncertainty principle, which states that the position and momentum of a particle cannot be simultaneously measured with arbitrary precision. Erwin Schrödinger and Paul Dirac contributed to the development of wave mechanics and quantum electrodynamics, respectively.The discovery of the electron by J.J. Thomson in 1897 paved the way for further exploration of atomic structure. Ernest Rutherford's gold foil experiment in 1911 demonstrated that atoms have a small, dense nucleus attheir center. Niels Bohr proposed the Bohr model of the atom in 1913, which described electrons orbiting the nucleus in discrete energy levels. This model was laterrefined with the development of quantum mechanics.In the field of particle physics, the 20th century witnessed the discovery of several subatomic particles. The electron, proton, and neutron were identified early on, but further research revealed a plethora of other particles. The development of particle accelerators, such as the cyclotron and later the Large Hadron Collider (LHC), allowed scientists to study these particles in greater detail. The discovery of the positron by Carl Anderson in 1932 and the subsequent development of antimatter theory by Paul Dirac were significant milestones in particle physics.The 20th century also saw the birth of nuclear physics. In 1919, Ernest Rutherford successfully transmuted one element into another, demonstrating the first artificial nuclear reaction. This led to the discovery of isotopes and the understanding of nuclear decay. In the 1930s, the concept of nuclear fission was proposed, and its practical application as a source of energy was realized with the development of the atomic bomb during World War II. Later, the peaceful use of nuclear energy for electricitygeneration was explored, leading to the construction of nuclear power plants.Notable physicists who made significant contributions during the 20th century include Albert Einstein, Niels Bohr, Werner Heisenberg, Erwin Schrödinger, Max Planck, Marie Curie, Richard Feynman, and many others. Their research and theories have had a profound impact on various scientific disciplines and technological advancements.In conclusion, the 20th century was a remarkable erafor physics, witnessing the emergence of theories such as relativity and quantum mechanics, the exploration of atomic and subatomic particles, and the development of nuclear physics. The contributions of numerous physicists duringthis time have shaped our understanding of the universe and paved the way for further scientific advancements.。

气科院大气物理面试英语专业词汇[1]

大气科学系微机应用基础Primer of microcomputer applicationFORTRAN77程序设计FORTRAN77 Program Design大气科学概论An Introduction to Atmospheric Science大气探测学基础Atmospheric Sounding流体力学Fluid Dynamics天气学Synoptic Meteorology天气分析预报实验Forecast and Synoptic analysis生产实习Daily weather forecasting现代气候学基础An introduction to modern climatology卫星气象学Satellite meteorologyC语言程序设计 C Programming大气探测实验Experiment on Atmospheric Detective Technique云雾物理学Physics of Clouds and fogs动力气象学Dynamic Meteorology计算方法Calculation Method诊断分析Diagnostic Analysis中尺度气象学Meso-Microscale Synoptic Meteorology边界层气象学Boundary Layer Meteorology雷达气象学Radar Meteorology数值天气预报Numerical Weather Prediction气象统计预报Meteorological Statical Prediction大气科学中的数学方法Mathematical Methods in Atmospheric Sciences专题讲座Seminar专业英语English for Meteorological Field of Study计算机图形基础Basic of computer graphics气象业务自动化Automatic Weather Service空气污染预测与防治Prediction and Control for Air Pollution现代大气探测Advanced Atmospheric Sounding数字电子技术基础Basic of Digital Electronic Techniqul大气遥感Remote Sensing of Atmosphere模拟电子技术基础Analog Electron Technical Base大气化学Atmospheric Chemistry航空气象学Areameteorology计算机程序设计Computer Program Design数值预报模式与数值模拟Numerical Model and Numerical Simulation接口技术在大气科学中的应用Technology of Interface in Atmosphere Sciences Application海洋气象学Oceanic Meteorology现代实时天气预报技术（MICAPS系统）Advanced Short-range Weather Forecasting Technique(MICAPS system)1) atmospheric precipitation大气降水2) atmosphere science大气科学3) atmosphere大气1.The monitoring and study of atmosphere characteristics in near space as an environment forspace weapon equipments and system have been regarded more important for battle support.随着临近空间飞行器的不断发展和运用,作为武器装备和系统环境的临近空间大气特性成为作战保障的重要条件。

著名数学家弗里曼 - 物理实验

著名数学家弗里曼·戴森的演讲译文：鸟和青蛙作者：弗里曼·戴森翻译：王丹红编辑按：弗里曼?戴森（Freeman Dyson）1923年12月15日出生，美籍英裔数学物理学家，普林斯顿高等研究院自然科学学院荣誉退休教授。

戴森早年在剑桥大学追随著名的数学家G.H.哈代研究数学，二战结束后来到美国康奈尔大学，跟随汉斯?贝特教授。

他证明了施温格和朝永振一郎发展的变分法方法和费曼的路径积分法的等价性，为量子电动力学的建立做出了决定性的贡献。

1951年他任康奈尔大学教授，1953年后一直任普林斯顿高等研究院教授。

《鸟和青蛙》(Birds and Frogs)是戴森应邀为美国数学会爱因斯坦讲座所起草的一篇演讲稿，该演讲计划于2008年10月举行，但因故被取消。

这篇文章全文发表于2009年2月出版的《美国数学会志》（NOTICES OF THE AMS, VOLUME56, Number 2）。

经美国数学会和戴森授权，科学时报记者王丹红全文翻译并在科学网上发布这篇文章。

有些数学家是鸟，其他的则是青蛙。

鸟翱翔在高高的天空，俯瞰延伸至遥远地平线的广袤的数学远景。

他们喜欢那些统一我们思想、并将不同领域的诸多问题整合起来的概念。

青蛙生活在天空下的泥地里，只看到周围生长的花儿。

他们乐于探索特定问题的细节，一次只解决一个问题。

我碰巧是一只青蛙，但我的许多最好朋友都是鸟。

这就是我今晚演讲的主题。

数学既需要鸟也需要青蛙。

数学丰富又美丽，因为鸟赋予它辽阔壮观的远景，青蛙则澄清了它错综复杂的细节。

数学既是伟大的艺术，也是重要的科学，因为它将普遍的概念与深邃的结构融合在一起。

如果声称鸟比青蛙更好，因为它们看得更遥远，或者青蛙比鸟更好，因为它们更加深刻，那么这些都是愚蠢的见解。

数学的世界既辽阔又深刻，我们需要鸟们和青蛙们协同努力来探索。

这个演讲被称为爱因斯坦讲座，应美国数学会之邀来这里演讲以纪念阿尔伯特?爱因斯坦，我深感荣幸。

天体物理学家英文

天体物理学家英文Astronomers are the intrepid explorers of the cosmos, delving into the mysteries of the universe with unwavering curiosity and scientific rigor. These dedicated individuals, known as astrophysicists, have dedicated their lives to unraveling the secrets of the celestial bodies that populate the vast expanse of the heavens.At the heart of an astrophysicist's work lies a deep fascination with the fundamental laws that govern the behavior of stars, galaxies, and the entire cosmic landscape. From the birth and evolution of stars to the nature of black holes and the origins of the universe itself, these scientists seek to uncover the underlying principles that shape the grand cosmic tapestry.One of the primary focuses of astrophysicists is the study of the formation and evolution of stars. By analyzing the spectral signatures and luminosities of these celestial beacons, they can piece together the intricate processes that govern a star's life cycle, from its fiery birth in clouds of gas and dust to its eventual demise, whether in a supernova explosion or a gradual fading into a dense remnant like a white dwarf or neutron star.This knowledge not only satisfies our innate curiosity about the cosmos but also has profound implications for our understanding of the universe and our place within it. The elements that make up our own planet and the very molecules that form the building blocks of life were forged in the nuclear furnaces of stars, and astrophysicists play a crucial role in tracing the origins of these essential materials.Beyond the study of individual stars, astrophysicists also delve into the complex dynamics of galaxies, both near and far. By observing the intricate patterns of motion and the distribution of matter within these vast stellar systems, they can uncover the hidden forces that shape the cosmic landscape, from the gravitational pull of dark matter to the influence of supermassive black holes at the centers of many galaxies.One of the most exciting frontiers in astrophysics is the search for exoplanets – planets orbiting stars other than our own Sun. By employing sophisticated techniques like the transit method and direct imaging, astrophysicists have discovered thousands of these distant worlds, opening up new avenues for understanding the diversity of planetary systems and the potential for extraterrestrial life.The quest to unravel the mysteries of the universe is not without its challenges, however. Astrophysicists must grapple with the vastscales and extreme conditions that characterize the cosmos, often relying on cutting-edge technologies and complex mathematical models to make sense of the data they collect. From the construction of powerful telescopes and space-based observatories to the development of sophisticated computer simulations, these scientists are constantly pushing the boundaries of what is possible in the pursuit of scientific knowledge.Yet, despite the inherent difficulties of their work, astrophysicists remain driven by a profound sense of wonder and a deep commitment to expanding the frontiers of human understanding. They are the modern-day explorers, charting the uncharted realms of the universe and inspiring generations of young minds to follow in their footsteps.As we continue to delve deeper into the cosmos, the role of the astrophysicist becomes ever more crucial. These dedicated individuals not only contribute to our scientific understanding but also shape our very conception of our place in the grand scheme of the universe. Their work not only satisfies our innate curiosity but also has the potential to unlock the secrets of our origins and the future of our existence.In the end, the pursuit of astrophysics is a testament to the human spirit – a relentless drive to explore, to understand, and to push theboundaries of what is known. It is a journey of discovery that continues to captivate and inspire, and astrophysicists are the intrepid trailblazers leading the way.。

史上作者最多的论文

Physics Letters B 688(2010)21–42Contents lists available at ScienceDirectPhysics Letters B/locate/physletbCharged-particle multiplicities in pp interactions at √s =900GeV measuredwith the ATLAS detector at the LHC ✩,✩✩ATLAS Collaborationa r t i c l e i n f o ab s t r ac t Article history:Received 16March 2010Received in revised form 22March 2010Accepted 22March 2010Available online 28March 2010Editor:W.-D.SchlatterKeywords:Charged-particleMultiplicities900GeVATLASLHCMinimum bias The ﬁrst measurements from proton–proton collisions recorded with the ATLAS detector at the LHC are presented.Data were collected in December 2009using a minimum-bias trigger during collisions at a centre-of-mass energy of 900GeV.The charged-particle multiplicity,its dependence on transverse momentum and pseudorapidity,and the relationship between mean transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range |η|<2.5and p T >500MeV.The measurements are compared to Monte Carlo models of proton–proton collisions and to results from other experiments at the same centre-of-mass energy.The charged-particle multiplicity per event and unit of pseudorapidity at η=0is measured to be 1.333±0.003(stat.)±0.040(syst.),which is 5–15%higher than the Monte Carlo models predict.2010Published by Elsevier B.V.1.IntroductionInclusive charged-particle distributions have been measured in pp and p ¯pcollisions at a range of different centre-of-mass energies [1–13].Many of these measurements have been used to constrain phenomenological models of soft-hadronic interactions and to predict properties at higher centre-of-mass energies.Most of the previous charged-particle multiplicity measurements were obtained by selecting data with a double-arm coincidence trigger,thus removing large fractions of diffractive events.The data were then further corrected to remove the remaining single-diffractive component.This selection is referred to as non-single-diffractive (NSD).In some cases,designated as inelastic non-diffractive,the residual double-diffractive component was also subtracted.The selection of NSD or inelastic non-diffractive charged-particle spectra involves model-dependent corrections for the diffractive components and for effects of the trigger selection on events with no charged particles within the acceptance of the detector.The measurement presented in this Letter implements a different strategy,which uses a single-arm trigger overlapping with the acceptance of the tracking volume.Results are presented as inclusive-inelastic distributions,with minimal model-dependence,by requiring one charged particle within the acceptance of the measurement.This Letter reports on a measurement of primary charged particles with a momentum component transverse to the beam direction 1p T >500MeV and in the pseudorapidity range |η|<2.5.Primary charged particles are deﬁned as charged particles with a mean lifetime τ>0.3×10−10s directly produced in pp interactions or from subsequent decays of particles with a shorter lifetime.The distributions of tracks reconstructed in the ATLAS inner detector were corrected to obtain the particle-level distributions:1N ev ·d N ch d η,1N ev ·12πp T ·d 2N ch d ηd p T ,1N ev ·d N ev d n ch and p T vs.n ch ,where N ev is the number of events with at least one charged particle inside the selected kinematic range,N ch is the total number of charged particles,n ch is the number of charged particles in an event and p T is the average p T for a given number of charged particles.✩©CERN,for the beneﬁt of the ATLAS Collaboration.✩✩Date submitted:2010-03-16T16:00:52Z.E-mail address:atlas.secretariat@cern.ch.1The ATLAS reference system is a Cartesian right-handed co-ordinate system,with the nominal collision point at the origin.The anti-clockwise beam direction deﬁnes the positive z -axis,while the positive x -axis is deﬁned as pointing from the collision point to the centre of the LHC ring and the positive y -axis points upwards.The azimuthal angle φis measured around the beam axis,and the polar angle θis measured with respect to the z -axis.The pseudorapidity is deﬁned as η=−ln tan (θ/2).0370-2693/$–see front matter 2010Published by Elsevier B.V.doi:10.1016/j.physletb.2010.03.06422ATLAS Collaboration/Physics Letters B688(2010)21–42Comparisons are made to previous measurements of charged-particle multiplicities in pp and p¯p collisions at √s=900GeV centre-of-mass energies[1,5]and to Monte Carlo(MC)models.2.The ATLAS detectorThe ATLAS detector[14]at the Large Hadron Collider(LHC)[15]covers almost the whole solid angle around the collision point with layers of tracking detectors,calorimeters and muon chambers.It has been designed to study a wide range of physics topics at LHC energies. For the measurements presented in this Letter,the tracking devices and the trigger system were of particular importance.The ATLAS inner detector has full coverage inφand covers the pseudorapidity range|η|<2.5.It consists of a silicon pixel detector (Pixel),a silicon microstrip detector(SCT)and a transition radiation tracker(TRT).These detectors cover a sensitive radial distance from the interaction point of50.5–150mm,299–560mm and563–1066mm,respectively,and are immersed in a2T axial magneticﬁeld. The inner-detector barrel(end-cap)parts consist of3(2×3)Pixel layers,4(2×9)double-layers of single-sided silicon microstrips with a40mrad stereo angle,and73(2×160)layers of TRT straws.These detectors have position resolutions of typically10,17and130μm for the R–φco-ordinate and,in case of the Pixel and SCT,115and580μm for the second measured co-ordinate.A track from a particle traversing the barrel detector would typically have11silicon hits(3pixel clusters and8strip clusters),and more than30straw hits.The ATLAS detector has a three-level trigger system:Level1(L1),Level2(L2)and Event Filter(EF).For this measurement,the trigger relies on the L1signals from the Beam Pickup Timing devices(BPTX)and the Minimum Bias Trigger Scintillators(MBTS).The BPTX are composed of beam pick-ups attached to the beam pipe±175m from the centre of the ATLAS detector.The MBTS are mounted at each end of the detector in front of the liquid-argon end-cap calorimeter cryostats at z=±3.56m and are segmented into eight sectors in azimuth and two rings in pseudorapidity(2.09<|η|<2.82and2.82<|η|<3.84).Data were collected for this analysis using the MBTS trigger,formed from BPTX and MBTS trigger signals.The MBTS trigger was conﬁgured to require one hit above threshold from either side of the detector.The eﬃciency of this trigger was studied with a separate prescaled L1BPTX trigger,ﬁltered to obtain inelastic interactions by inner detector requirements at L2and EF.3.Monte Carlo simulationLow-p T scattering processes may be described by lowest-order perturbative Quantum Chromodynamics(QCD)two-to-two parton scat-ters,where the divergence of the cross section at p T=0is regulated by phenomenological models.These models include multiple-parton scattering,partonic-matter distributions,scattering between the unresolved protons and colour reconnection[16].The PYTHIA[17]MC event generator implements several of these models.The parameters of these models have been tuned to describe charged-hadron pro-duction and the underlying event in pp and p¯p data at centre-of-mass energies between200GeV and1.96TeV.Samples of ten million MC events were produced for single-diffractive,double-diffractive and non-diffractive processes using the PYTHIA6.4.21generator.A speciﬁc set of optimised parameters,the ATLAS MC09PYTHIA tune[18],which employs the MRST LO*parton density functions[19]and the p T-ordered parton shower,is the reference tune throughout this Letter.These parameters were derived by tuning to underlying event and minimum-bias data from Tevatron at630GeV and1.8TeV.The MC samples generated with this tune were used to determine detector acceptances and eﬃciencies and to correct the data.For the purpose of comparing the present measurement to different phenomenological models describing minimum-bias events,the following additional MC samples were generated:the ATLAS MC09c[18]PYTHIA tune,which is an extension of the ATLAS MC09tune optimising the strength of the colour reconnection to describe the p T distributions as a function of n ch,as measured by CDF in p¯p collisions[3];the Perugia0[20]PYTHIA tune,in which the soft-QCD part is tuned using only minimum-bias data from the Tevatron and CERN p¯p colliders;the DW[21]PYTHIA tune,which uses the virtuality-ordered showers and was derived to describe the CDF Run II underlying event and Drell–Yan data.Finally,the PHOJET generator[22]was used as an alternative model.It describes low-p T physics using the two-component Dual Parton Model[23,24],which includes soft hadronic processes described by Pomeron exchange and semi-hard processes described by perturbative parton scattering.PHOJET relies on PYTHIA for the fragmentation of partons.The versions2used for this study were shown to agree with previous measurements[3,5,6,9].The non-diffractive,single-diffractive and double-diffractive contributions in the generated samples were mixed according to the gen-erator cross sections to fully describe the inelastic scattering.All the events were processed through the ATLAS detector simulation program[25],which is based on Geant4[26].They were then reconstructed and analysed by the same program chain used for the data.Particular attention was devoted to the description in the simulation of the size and position of the collision beam spot and of the detailed detector conditions during data taking.4.Event selectionAll data recorded during the stable LHC running periods between December6and15,2009,in which the inner detector was fully operational and the solenoid magnet was on,were used for this analysis.During this period the beams were colliding head-on in ATLAS.A total of455,593events were collected from colliding proton bunches in which the MBTS trigger recorded one or more counters above threshold on either side.In order to perform an inclusive-inelastic measurement,no further requirements beyond the MBTS trigger and inner detector information were applied in this event selection.The integrated luminosity for theﬁnal event sample,which is given here for reference only,was estimated using a sample of events with energy deposits in both sides of the forward and end-cap calorimeters. The MC-based eﬃciency and the PYTHIA default cross section of52.5mb were then used to determine the luminosity of the data sample to be approximately9μb−1,while the maximum instantaneous luminosity was approximately5×1026cm−2s−1.The probability of additional interactions in the same bunch crossing was estimated to be less than0.1%.2PHOJET1.12with PYTHIA6.4.21.ATLAS Collaboration/Physics Letters B688(2010)21–4223parison between data(dots)and minimum-bias ATLAS MC09simulation(histograms)for the average number of Pixel hits(a)and SCT hits(b)per track as a function ofη,and the transverse(c)and longitudinal(d)impact parameter distributions of the reconstructed tracks.The MC distributions in(c)and(d)are normalised to the number of tracks in the data.The inserts in the lower panels show the distributions in logarithmic scale.During this data-taking period,more than96%of the Pixel detector,99%of the SCT and98%of the TRT were operational.Tracks were reconstructed oﬄine within the full acceptance range|η|<2.5of the inner detector[27,28].Track candidates were reconstructed by requiring seven or more silicon hits in total in the Pixel and SCT,and then extrapolated to include measurements in the TRT.Typically, 88%of tracks inside the TRT acceptance(|η|<2)include a TRT extension,which signiﬁcantly improves the momentum resolution.This Letter reports results for charged particles with p T>500MeV,which are less prone than lower-p T particles to large ineﬃciencies and their associated systematic uncertainties resulting from interactions with material inside the tracking volume.To reduce the contri-bution from background events and non-primary tracks,as well as to minimise the systematic uncertainties,the following criteria were required:•the presence of a primary vertex[29]reconstructed using at least three tracks,each with:—p T>150MeV,—a transverse distance of closest approach with respect to the beam-spot position|d BS0|<4mm;•at least one track with:—p T>500MeV,—a minimum of one Pixel and six SCT hits,—transverse and longitudinal impact parameters calculated with respect to the event primary vertex|d0|<1.5mm and|z0|·sinθ<1.5mm,respectively.These latter tracks were used to produce the corrected distributions and will be referred to as selected tracks.The multiplicity of selected tracks within an event is denoted by n Sel.In total326,201events were kept after this oﬄine selection,which contained1,863,622 selected tracks.The inner detector performance is illustrated in Fig.1using selected tracks and their MC simulation.The shapes from overlapping Pixel and SCT modules in the forward region and the ineﬃciency from a small number of disabled Pixel modules in the central region are well modelled by the simulation.The simulated impact-parameter distributions describe the data to better than10%, including their tails as shown in the inserts of Fig.1(c)and(d).The difference between data and MC observed in the central region of the d0distribution is due to small residual misalignments not simulated in the MC,which are found to be unimportant for this analysis.Trigger and vertex-reconstruction eﬃciencies were parameterized as a function of the number of tracks passing all of the track selection requirements except for the constraints with respect to the primary vertex.Instead,the transverse impact parameter with respect to the beam spot was required to be less than4mm,which is the same requirement as that used in the primary vertex reconstruction preselection.The multiplicity of these tracks in an event is denoted by n BS.Sel24ATLAS Collaboration /Physics Letters B 688(2010)21–425.Background contributionThere are two possible sources of background events that can contaminate the selected sample:cosmic rays and beam-induced back-ground.A limit on the fraction of cosmic-ray events recorded by the L1MBTS trigger during data taking was determined from cosmic-ray studies,the maximum number of proton bunches,and the central trigger processor clock width of 25ns,and was found to be smaller than 10−6.Beam-induced background events can be produced by proton collisions with upstream collimators or with residual particles inside the beam pipe.The L1MBTS trigger was used to select beam-induced background events from un-paired proton bunch-crossings.By ap-plying the analysis selection criteria to these events,an upper limit of 10−4was determined for the fraction of beam-induced background events within the selected sample.The requirement of a reconstructed primary vertex is particularly useful to suppress the beam-induced background.Primary charged-particle multiplicities are measured from selected-track distributions after correcting for the fraction of secondary particles in the sample.The potential background from fake tracks is found to be less than 0.1%from simulation studies.Non-primary tracks are mostly due to hadronic interactions,photon conversions and decays of long-lived particles.Their contribution was estimated using the MC prediction of the shape of the d 0distribution,after normalising to data for tracks within 2mm <|d 0|<10mm,i.e.outside the range used for selecting tracks.The simulation was found to reproduce the tails of the d 0distribution of the data,as shown in Fig.1(c),and the normalisation factor between data and MC was measured to be 1.00±0.02(stat.)±0.05(syst.).The MC was then used to estimate the fraction of secondaries in the selected-track sample to be (2.20±0.05(stat.)±0.11(syst.))%.This fraction is independent of n Sel ,but shows a dependence on p T and a small dependence on η.While the correction for secondaries was applied in bins of p T ,the dependence on ηwas incorporated into the systematic uncertainty.6.Selection eﬃciencyThe data were corrected to obtain inclusive spectra for charged primary particles satisfying the event-level requirement of at least one primary charged particle within p T >500MeV and |η|<2.5.These corrections include ineﬃciencies due to trigger selection,vertex and track reconstruction.They also account for effects due to the momentum scale and resolution,and for the residual background from secondary tracks.Trigger eﬃciency The trigger eﬃciency was measured from an independent data sample selected using the control trigger introduced in Section 2.This control trigger required more than 6Pixel clusters and 6SCT hits at L2,and one or more reconstructed tracks with p T >200MeV at the EF.The vertex requirement for selected tracks was removed for this study,to avoid correlations between the trigger and vertex-reconstruction eﬃciencies for L1MBTS triggered events.The trigger eﬃciency was determined by taking the ratio of events from the control trigger in which the L1MBTS also accepted the event,over the total number of events in the control sample.The result is shown in Fig.2(a)as a function of n BS Sel .The trigger eﬃciency is nearly 100%everywhere and the requirement of this trigger does not affect the p T and ηtrack distributions of the selected events.Vertex-reconstruction eﬃciency The vertex-reconstruction eﬃciency was determined from the data,by taking the ratio of triggered eventswith a reconstructed vertex to the total number of triggered events.It is shown in Fig.2(b)as a function of n BSSel .The eﬃciency amounts to approximately 67%for the lowest bin and rapidly rises to 100%with higher multiplicities.The dependence of the vertex-reconstructioneﬃciency on the ηand p T of the selected tracks was studied.The ηdependence was found to be approximately ﬂat for n BS Sel>1and to decrease at larger ηfor events with n BS Sel=1.This dependence was corrected for.No dependence on p T was observed.Track-reconstruction eﬃciency The track-reconstruction eﬃciency in each bin of the p T –ηacceptance was determined from MC.The com-parison of the MC and data distributions shown in Fig.1highlights their agreement.The track-reconstruction eﬃciency was deﬁned as:bin (p T ,η)=N matched rec (p T ,η)N gen (p T ,η),where p T and ηare generated quantities,and N matched rec (p T ,η)and N gen (p T ,η)are the number of reconstructed tracks in a given binmatched to a generated charged particle and the number of generated charged particles in that bin,respectively.The matching between a generated particle and a reconstructed track was done using a cone-matching algorithm in the η–φplane,associating the particle to the track with the smallest R = ( φ)2+( η)2within a cone of radius 0.05.The resulting reconstruction eﬃciency as a function of p T integrated over ηis shown in Fig.2(c).The drop to ≈70%for p T <600MeV is an artefact of the p T cut at the pattern-recognition level and is discussed in Section 8.The reduced track-reconstruction eﬃciency in the region |η|>1(Fig.2(d))is mainly due to the presence of more material in this region.These ineﬃciencies include a 5%loss due to the track selection used in this analysis,approximately half of which is due to the silicon-hit requirements and half to the impact-parameter requirements.7.Correction procedureThe effect of events lost due to the trigger and vertex requirements can be corrected for using an event-by-event weight:w ev n BSSel =1 trig (n BS Sel )·1 vtx (n BS Sel ),where trig (n BS Sel )and vtx (n BS Sel )are the trigger and vertex reconstruction eﬃciencies discussed in Section 6.The vertex-reconstruction eﬃciency for events with n BSSel=1includes an η-dependent correction which was derived from the data.ATLAS Collaboration/Physics Letters B688(2010)21–4225Fig.2.Trigger(a)and vertex-reconstruction(b)eﬃciencies as a function of the variable n BSSel deﬁned in Section4;track-reconstruction eﬃciency as a function of p T(c)andofη(d).The vertical bars represent the statistical uncertainty,while the shaded areas represent the statistical and systematic uncertainties added in quadrature.The two bottom panels were derived from the PYTHIA ATLAS MC09sample.The p T andηdistributions of selected tracks were corrected on a track-by-track basis using the weight:w trk(p T,η)=1bin(p T,η)·1−f sec(p T)·1−f okr(p T,η),where bin is the track-reconstruction eﬃciency described in Section6and f sec(p T)is the fraction of secondaries determined as described in Section5.The fraction of selected tracks for which the corresponding primary particles are outside the kinematic range,f okr(p T,η), originates from resolution effects and has been estimated from MC.Bin migrations were found to be due solely to reconstructed track momentum resolution and were corrected by using the resolution function taken from MC.In the case of the distributions versus n ch,a track-level correction was applied by using Bayesian unfolding[30]to correct back to the number of charged particles.A matrix M ch,Sel,which expresses the probability that a multiplicity of selected tracks n Sel is due to n ch particles,was populated using MC and applied to obtain the n ch distribution from the data.The resulting distribution was then used to re-populate the matrix and the correction was re-applied.This procedure was repeated without a regularisation term and converged after four iterations,when the change in the distribution between iterations was found to be less than1%.It should be noted that the matrix cannot correct for events which are lost due to track-reconstruction ineﬃciency.To correct for these missing events,a correction factor 1/(1−(1− (n ch))n ch)was applied,where (n ch)is the average track-reconstruction eﬃciency.In the case of the p T versus n ch distribution,each event was weighted by w ev(n BS Sel).For each n Sel a MC-based correction was applied to convert the reconstructed average p T to the average p T of primary charged particles.Then the matrix M ch,Sel was applied as described above.8.Systematic uncertaintiesNumerous detailed studies have been performed to understand possible sources of systematic uncertainties.The main contributions are discussed below.26ATLAS Collaboration/Physics Letters B688(2010)21–42Trigger The trigger selection dependence on the p T andηdistributions of reconstructed tracks was found to beﬂat within the statistical uncertainties of the data recorded with the control trigger.The statistical uncertainty on this result was taken as a systematic uncertainty of0.1%on the overall trigger eﬃciency.Since there is no vertex requirement in the data sample used to measure the trigger eﬃciency,it is not possible to make the same impact-parameter cuts as are made on theﬁnal selected tracks.Therefore the trigger eﬃciency was measured using impact-parameter constraints with respect to the primary vertex or the beam spot and compared to that obtained without such a requirement.The differencewas taken as a systematic uncertainty of0.1%for n BSSel 3.The correlation of the MBTS trigger with the control trigger used to select the data sample for the trigger-eﬃciency determination was studied using the simulation.The resulting systematic uncertainty was found to affect only the case n BSSel=1and amounts to0.2%.Vertex reconstruction The run-to-run variation of the vertex-reconstruction eﬃciency was found to be within the statistical uncertainty. The contribution of beam-related backgrounds to the sample selected without a vertex requirement was estimated by using non-collidingbunches.It was found to be0.3%for n BSSel =1and smaller than0.1%for higher multiplicities,and was assigned as a systematic uncertainty.This background contribution is larger than that given in Section5,since a reconstructed primary vertex was not required for these events.Track reconstruction and selection Since the track-reconstruction eﬃciency is determined from MC,the main systematic uncertainty results from the level of disagreement between data and MC.Three different techniques to associate generated particles to reconstructed tracks were studied:a cone-matching algorithm,an eval-uation of the fraction of simulated hits associated to a reconstructed track and an inclusive technique using a correction for secondary particles.A systematic uncertainty of0.5%was assigned from the difference between the cone-matching and the hit-association methods.A detailed comparison of track properties in data and simulation was performed by varying the track-selection criteria.The largest deviations between data and MC were observed by varying the z0·sinθselection requirement,and by varying the constraint on the number of SCT hits.These deviations are generally smaller than1%and rise to3%at the edges of theηrange.The systematic effects of misalignment were studied by smearing simulation samples by the expected residual misalignment and by comparing the performance of two alignment algorithms on tracks reconstructed from the data.Under these conditions the number of reconstructed tracks was measured and the systematic uncertainty on the track reconstruction eﬃciency due to the residual misalignment was estimated to be less than1%.To test the inﬂuence of an imperfect description of the detector material in the simulation,two additional MC samples with approx-imately10%and20%increase in radiation lengths of the material in the Pixel and SCT active volume were used.The impact of excess material in the tracking detectors was studied using the tails of the impact-parameter distribution,the length of tracks,and the change inthe reconstructed K0S mass as a function of the decay radius,the direction and the momentum of the K0S.The MC with nominal materialwas found to describe the data best.The data were found to be consistent with a10%material increase in some regions,whereas the 20%increase was excluded in all cases.The eﬃciency of matching full tracks to track segments reconstructed in the Pixel detector was also studied.The comparison between data and simulation was found to have good agreement across most of the kinematic range.Some discrepancies found for|η|>1.6were included in the systematic uncertainties.From all these studies a systematic uncertainty on the track reconstruction eﬃciency of3.7%,5.5%and8%was assigned to the pseudorapidity regions|η|<1.6,1.6<|η|<2.3and|η|>2.3, respectively.The track-reconstruction eﬃciency shown in Fig.2(c)rises sharply in the region500<p T<600MeV.The observed turn-on curve is produced by the initial pattern recognition step of track reconstruction and its associated p T resolution,which is considerably worse than theﬁnal p T resolution.The consequence is that some particles which are simulated with p T>500MeV are reconstructed with momenta below the selection requirement.This effect reduces the number of selected tracks.The shape of the threshold was studied in data and simulation and a systematic uncertainty of5%was assigned to theﬁrst p T bin.In conclusion,an overall relative systematic uncertainty of4.0%was assigned to the track reconstruction eﬃciency for most of the kinematic range of this measurement,while8.5%and6.9%were assigned to the highest|η|and to the lowest p T bins,respectively.Momentum scale and resolution To obtain corrected distributions of charged particles,the scale and resolution uncertainties in the recon-structed p T andηof the selected tracks have to be taken into account.Whereas the uncertainties for theηmeasurement were found to be negligible,those for the p T measurement are in general more important.The inner detector momentum resolution was taken from MC as a function of p T andη.It was found to vary between1.5%and5%in the range relevant to this analysis.The uncertainty was estimated by comparing with MC samples with a uniform scaling of10%additional material at low p T and with large misalignments at higher p T. Studies of the width of the mass peak for reconstructed K0Scandidates in the data show that these assumptions are conservative.Thereconstructed momentum scale was checked by comparing the measured value of the K0S mass to the MC.The systematic uncertaintiesfrom both the momentum resolution and scale were found to have no signiﬁcant effect on theﬁnal results.Fraction of secondaries The fraction of secondaries was determined as discussed in Section5.The associated systematic uncertainty was estimated by varying the range of the impact parameter distribution that was used to normalise the MC,and byﬁtting separate distribu-tions for weak decays and material interactions.The systematic uncertainty includes a small contribution due to theηdependence of this correction.The total uncertainty is0.1%.Correction procedure Several independent tests were made to assess the model dependence of the correction matrix M ch,Sel and the resulting systematic uncertainty.In order to determine the sensitivity to the p T andηdistributions,the matrix was re-populated using the other MC parameterizations described in Section3and by varying the track-reconstruction eﬃciency by±5%.The correction factor for events lost due to the track-reconstruction ineﬃciency was varied by the same amount and treated as fully correlated.For the overall normalisation,this leads to an uncertainty of0.4%due to the model dependence and of1.1%due to the track-reconstruction eﬃciency. The size of the systematic uncertainties on n ch increases with the multiplicity.。

托福阅读tpo70第一篇

物理科普小报的制作过程英文回答：The process of creating a physics popular science newsletter involves several steps. Firstly, I need to choose a topic that is interesting and relevant to the readers. This could be anything from explaining the concept of gravity to discussing the latest discoveries in quantum physics. Once I have decided on a topic, I conduct thorough research to gather accurate and up-to-date information.Next, I organize the information into a coherent structure. I start with an introduction that grabs the readers' attention and provides a brief overview of the topic. Then, I delve into the details, explaining the key concepts and theories in a clear and concise manner. I make sure to use simple language and avoid jargon, so that the content is accessible to a wide audience.To make the newsletter more engaging, I includeexamples and anecdotes that help illustrate the concepts. For instance, when explaining the theory of relativity, I might use the famous example of a spaceship traveling near the speed of light and how time dilation occurs. These examples not only make the content more relatable but also help the readers grasp complex ideas more easily.After writing the main content, I proofread and editthe newsletter to ensure it is free of errors and flows smoothly. I pay attention to the overall structure, grammar, and punctuation. Additionally, I make sure to include relevant visuals such as diagrams, graphs, or images to enhance the understanding of the concepts.Finally, I design the layout of the newsletter, taking into consideration the readability and aesthetics. I choose an appropriate font, font size, and color scheme that complement the content. I also make sure to include headings, subheadings, and bullet points to make the information more organized and visually appealing.中文回答：制作物理科普小报的过程包括几个步骤。

法布里珀罗基模共振英文

法布里珀罗基模共振英文The Fabryperot ResonanceOptics, the study of light and its properties, has been a subject of fascination for scientists and researchers for centuries. One of the fundamental phenomena in optics is the Fabry-Perot resonance, named after the French physicists Charles Fabry and Alfred Perot, who first described it in the late 19th century. This resonance effect has numerous applications in various fields, ranging from telecommunications to quantum physics, and its understanding is crucial in the development of advanced optical technologies.The Fabry-Perot resonance occurs when light is reflected multiple times between two parallel, partially reflective surfaces, known as mirrors. This creates a standing wave pattern within the cavity formed by the mirrors, where the light waves interfere constructively and destructively to produce a series of sharp peaks and valleys in the transmitted and reflected light intensity. The specific wavelengths at which the constructive interference occurs are known as the resonant wavelengths of the Fabry-Perot cavity.The resonant wavelengths of a Fabry-Perot cavity are determined bythe distance between the mirrors, the refractive index of the material within the cavity, and the wavelength of the incident light. When the optical path length, which is the product of the refractive index and the physical distance between the mirrors, is an integer multiple of the wavelength of the incident light, the light waves interfere constructively, resulting in a high-intensity transmission through the cavity. Conversely, when the optical path length is not an integer multiple of the wavelength, the light waves interfere destructively, leading to a low-intensity transmission.The sharpness of the resonant peaks in a Fabry-Perot cavity is determined by the reflectivity of the mirrors. Highly reflective mirrors result in a higher finesse, which is a measure of the ratio of the spacing between the resonant peaks to their width. This high finesse allows for the creation of narrow-linewidth, high-resolution optical filters and laser cavities, which are essential components in various optical systems.One of the key applications of the Fabry-Perot resonance is in the field of optical telecommunications. Fiber-optic communication systems often utilize Fabry-Perot filters to select specific wavelength channels for data transmission, enabling the efficient use of the available bandwidth in fiber-optic networks. These filters can be tuned by adjusting the mirror separation or the refractive index of the cavity, allowing for dynamic wavelength selection andreconfiguration of the communication system.Another important application of the Fabry-Perot resonance is in the field of laser technology. Fabry-Perot cavities are commonly used as the optical resonator in various types of lasers, providing the necessary feedback to sustain the lasing process. The high finesse of the Fabry-Perot cavity allows for the generation of highly monochromatic and coherent light, which is crucial for applications such as spectroscopy, interferometry, and precision metrology.In the realm of quantum physics, the Fabry-Perot resonance plays a crucial role in the study of cavity quantum electrodynamics (cQED). In cQED, atoms or other quantum systems are placed inside a Fabry-Perot cavity, where the strong interaction between the atoms and the confined electromagnetic field can lead to the observation of fascinating quantum phenomena, such as the Purcell effect, vacuum Rabi oscillations, and the generation of nonclassical states of light.Furthermore, the Fabry-Perot resonance has found applications in the field of optical sensing, where it is used to detect small changes in physical parameters, such as displacement, pressure, or temperature. The high sensitivity and stability of Fabry-Perot interferometers make them valuable tools in various sensing and measurement applications, ranging from seismic monitoring to the detection of gravitational waves.The Fabry-Perot resonance is a fundamental concept in optics that has enabled the development of numerous advanced optical technologies. Its versatility and importance in various fields of science and engineering have made it a subject of continuous research and innovation. As the field of optics continues to advance, the Fabry-Perot resonance will undoubtedly play an increasingly crucial role in shaping the future of optical systems and applications.。

哥白尼简介英文

哥白尼简介英文Copernicus: A Revolution in AstronomyNicolaus Copernicus, also known as Mikolaj Kopernik in Polish, was a renowned astronomer, mathematician, and cleric. Born on February 19, 1473 in Torun, Poland, Copernicus is widely regarded as the founder of modern astronomy. His groundbreaking work on heliocentrism challenged the prevailing geocentric model of the universe and revolutionized our understanding of the cosmos. This essay aims to provide a comprehensive overview of Copernicus's life, his achievements, and the impact of his work on the field of astronomy.Copernicus came from a noble family and received a solid education from an early age. He studied at the University of Krakow, where he exhibited exceptional talent in mathematics and astronomy. In 1491, he traveled to Italy to further his studies. He attended the University of Bologna, where he studied canon law and medicine, and later studied mathematics and astronomy at the University of Padua. During his time in Italy, Copernicus had the opportunity to engage with the leading intellectuals and scholars of the time, which greatly influenced his thinking.One of Copernicus's most significant contributions to the field of astronomy was his heliocentric model of the universe, which he first outlined in his seminal work, "De Revolutionibus Orbium Coelestium" (On the Revolutions of the Celestial Spheres). Published in 1543, this revolutionary book presented his radical theory that the Earth revolves around the Sun, challenging the prevailing geocentric belief that the Earth was the center of theuniverse.Copernicus's heliocentric model was not entirely original. Ancient Greek astronomers, such as Aristarchus of Samos, had proposed similar ideas centuries earlier. However, Copernicus's meticulous observations and calculations provided the scientific foundation for his theory. He argued that the Earth's rotation on its axis and its orbit around the Sun explained the apparent motion of the celestial bodies, such as the planets.Despite his groundbreaking work, Copernicus did not escape controversy and criticism. His heliocentric model directly contradicted the teachings of the Catholic Church, which supported the geocentric model based on religious and philosophical grounds. However, Copernicus managed to navigate this delicate situation by dedicating his book to Pope Paul III, who showed a degree of support for his work. Nevertheless, it was not until many years later, after Copernicus's death, that his ideas gained wider acceptance within the scientific community.The impact of Copernicus's heliocentric model cannot be overstated. His work laid the foundation for the scientific revolution that would follow in the centuries to come. The acceptance of heliocentrism led to a fundamental shift in our understanding of the universe and our place within it. Galileo Galilei, Johannes Kepler, and Isaac Newton built upon Copernicus's work, further refining our knowledge of celestial mechanics and orbital dynamics.Furthermore, Copernicus's heliocentric model had profoundimplications for the fields of mathematics and physics. It challenged traditional notions of motion and laid the groundwork for Newton's laws of motion and universal gravitation. The Copernican revolution marked a shift from an Earth-centered perspective to a more objective and scientific approach to understanding the natural world.It is worth noting that Copernicus's contributions extended beyond his work in astronomy. He was also a skilled mathematician, contributing to the fields of trigonometry and arithmetic. His expertise in economics and administration led him to serve as a financial advisor to the Polish royal family and as a diplomat. Copernicus's diverse interests and talents allowed him to make significant contributions in various domains throughout his life.In conclusion, Nicolaus Copernicus's life and work had a profound impact on the field of astronomy and beyond. His heliocentric model challenged long-held beliefs and laid the foundation for the scientific revolution. Copernicus's dedication to observation, meticulous calculations, and courage to challenge established dogma paved the way for future advancements in our understanding of the cosmos. His contributions continue to inspire generations of astronomers and scientists worldwide.Certainly! Here is the continuation of the essay:Another important aspect of Copernicus's work is his approach to observation and measurement. He was known for his meticulous and careful observations of the celestial bodies, which allowed him to gather accurate data for his calculations. Copernicus used various instruments, such as astrolabes and quadrants, to measurethe positions and movements of the planets and stars. His commitment to precise measurements laid the groundwork for the development of modern observational astronomy.Copernicus's work also had a significant impact on our understanding of the solar system. His heliocentric model provided a new perspective on the arrangement and motion of the planets. He argued that the planets, including Earth, revolve around the Sun in circular orbits. This explanation elegantly accounted for the observed phenomena, such as retrograde motion, more accurately than the complex epicycles of the geocentric model.Furthermore, Copernicus's theory allowed for a more coherent explanation of the sizes and distances of the planets. He calculated the relative distances of the planets from the Sun, known as their "astronomical units," and provided a rough estimate of their sizes. Although his measurements were not entirely accurate, they laid the foundation for subsequent astronomers to refine and improve upon his calculations.Copernicus's heliocentric model also challenged the traditional view of the celestial sphere. He proposed that the stars are immeasurably distant from the Earth and that they appear to move due to the Earth's rotation on its axis. This idea suggested an expanded understanding of the universe, with the Earth as just one celestial body among many. It broadened our perspective and challenged the notion that the Earth was the center of all creation. Although Copernicus's work was revolutionary, it took time for it to be widely accepted. The scientific community, as well as theCatholic Church, was initially skeptical of his ideas. Many astronomers and scholars adhered to the geocentric model, which had been the prevailing view for centuries. They also feared the social and theological implications of Copernicus's theory.However, with the passage of time and the accumulation of more observational evidence, Copernicus's heliocentric model gained acceptance. Astronomers such as Johannes Kepler and Galileo Galilei provided further evidence supporting the theory, through their own observations and calculations. Kepler's laws of planetary motion and Galileo's telescopic observations of the phases of Venus and the moons of Jupiter provided compelling evidence in favor of the heliocentric model.The Church's initial opposition to Copernicus's theory was primarily based on the biblical interpretation that the Earth was the fixed center of the universe. However, as more evidence supporting heliocentrism emerged, the Church gradually adjusted its stance. Eventually, in 1822, the Catholic Church removed Copernicus's book from its list of prohibited books, acknowledging his contributions to astronomy.Copernicus's impact on the field of astronomy extended well beyond his own time. His work laid the groundwork for the scientific advancements of the centuries that followed. The acceptance of heliocentrism opened the door for advancements in observational techniques, the development of new instruments, and the formulation of more accurate mathematical models for celestial motion.Copernicus's work also inspired further questions and investigations into the nature of the cosmos. His heliocentric model raised questions about the nature of gravity and the dynamics of the solar system. These questions led to the development of Newton's laws of motion and universal gravitation in the 17th century. Newton's work built upon Copernicus's foundation, providing a more comprehensive understanding of the forces governing the motion of celestial bodies.Copernicus's legacy continues to inspire astronomers and scientists today. His approach to observation, his commitment to empirical evidence, and his willingness to challenge established beliefs set an example for future generations of scientists. His work serves as a reminder of the importance of questioning and exploring the natural world, even if it means challenging prevailing views.In conclusion, Nicolaus Copernicus's contributions to astronomy and the scientific revolution cannot be overstated. His heliocentric model revolutionized our understanding of the universe and laid the foundation for future advancements in observational astronomy, celestial mechanics, and theories of gravity. Copernicus's dedication to observation, his meticulous calculations, and his courage to challenge established dogma continue to inspire scientists and shape our understanding of the cosmos to this day.。

介观物理的英文

介观物理的英文精选英文介观物理的英文：Introduction to PhysicsPhysics, a fundamental branch of natural science, explores the nature and properties of matter, energy, space, and time. It delves into the innermost workings of the universe, from the smallest particles that constitute matter to the largest structures in the cosmos. This discipline aims to understand the underlying principles governing the behavior of these entities and their interactions.The journey of physics begins with the study of classical mechanics, which describes the motion of objects and the forces that act upon them. Newton's laws of motion, for instance, provide a foundation for understanding how objects move and interact with each other. As we delve deeper, we encounter the laws of thermodynamics, which govern the transfer of heat and the behavior of systems in terms of energy.The realm of electromagnetism opens up a new dimension in physics. Maxwell's equations, which unify electricity and magnetism, form the backbone of modern electronics and telecommunications. These equations explain how electromagnetic waves propagate, including visible light, radio waves, and even the gamma rays emitted by stars.The advent of quantum mechanics revolutionized our understanding of the subatomic world. This theory, developed in the early 20th century, describes the behavior of particles and systems at the atomic and molecular level. It introduces concepts such as wave-particle duality and quantum entanglement, which challenge our traditional understanding of reality.Moreover, the field of relativity, pioneered by Einstein, revolutionized our comprehension of space and time. His special theory of relativity described how the perception of space and time changes with the speed of an observer, while his general theory of relativity explained gravity as a manifestation of the curvature of spacetime.Modern physics is a vast and ever-expanding field, with new discoveries and theories constantly shaping our understanding of the universe. It is not just a subject confined to textbooks and laboratories; it is a tool that has revolutionized technology, medicine, and even our daily lives. From the smartphones we carry to the satellites orbiting the Earth, the principles of physics are everywhere, shaping our world in immeasurable ways.In conclusion, physics is a discipline that strives to unravel the mysteries of the universe, from the microcosm to the macrocosm. It is an exciting journey that challenges our imagination and pushes the boundaries of human knowledge. Through the study of physics, we gain a deeper understanding of the world we live in and the infinite possibilities that lie ahead.中文对照翻译：物理学导论物理学是自然科学的一个基本分支，探索物质、能量、空间和时间的性质和性质。

用英语介绍物理学家爱因斯坦作文

用英语介绍物理学家爱因斯坦作文Albert Einstein was a towering figure in the world of physics, renowned for his groundbreaking theories that reshaped our understanding of the universe. His work on the theory of relativity, which includes the famous equationE=mc², revolutionized the field and earned him the Nobel Prize in Physics.Born in Ulm, Germany, in 1879, Einstein was a curious child with a passion for learning. He often found himself questioning the nature of things, a trait that would later lead him to challenge the established laws of physics. His early life was marked by a deep interest in mathematics and philosophy, which laid the foundation for his future scientific endeavors.Einstein's academic journey was not without its challenges. He faced difficulties in traditional education systems, which he found rigid and stifling. However, his persistence and independent thinking eventually led him to develop his own theories, which were initially met with skepticism but later gained widespread acceptance.His contributions to science extend beyond the realm of physics. Einstein was also a strong advocate for peace and humanitarian causes. He used his influence to speak out against war and promote international cooperation, demonstrating that his intellect was matched by acompassionate heart.Despite his fame, Einstein remained humble and focused on the pursuit of knowledge. He was known to say that he had no special talent but was merely passionately curious. This curiosity drove him to explore the mysteries of the cosmosand to challenge the limits of human understanding.Einstein's legacy continues to inspire scientists and thinkers alike. His life serves as a reminder that thepursuit of knowledge is a never-ending journey, and that even the most complex problems can be understood through curiosity, creativity, and perseverance.。

物理英语词汇树

物理英语词汇树The study of physics opens up a vast and intricate world of vocabulary, each term carefully crafted to precisely describe the myriad phenomena that govern our universe. This physical vocabulary tree is a testament to the intellectual rigor and depth of this field, branching out from fundamental concepts to the most specialized and technical terms.At the root of this tree lie the basic building blocks of our physical understanding - mass, energy, force, and time. These foundational ideas form the trunk from which the entire tree grows, providing the essential framework upon which more complex branches can develop. Mass, the fundamental measure of matter, is the essential quantity that defines the interaction of objects through the force of gravity. Energy, in its many forms, fuels the constant motion and change that characterizes the physical world. Force, the push or pull that can set objects in motion or maintain their state, is the engine that drives the mechanisms of the universe. And time, the inexorable march of moments that gives structure and order to all physical processes, is the dimension that binds everything together.Branching out from these core concepts, we find a rich diversity of vocabulary that describes the various states of matter - solid, liquid, and gas - and the properties that define them. Solids, with their rigid molecular structure and defined shape, contrast with the fluid nature of liquids and the expansive, formless quality of gases. Vocabulary such as density, viscosity, and compressibility precisely capture the unique characteristics of each state, allowing physicists to analyze and predict their behavior.As we move further up the tree, the branches grow more specialized, delving into the intricacies of motion and the forces that govern it. Velocity, acceleration, and momentum are the fundamental descriptors of movement, while concepts like inertia, friction, and torque explain the ways in which objects interact and respond to the world around them. The vocabulary of kinematics and dynamics provides the language to describe the complex dance of bodies in motion, from the most mundane objects to the celestial bodies that populate the cosmos.Extending from the motion-focused branches, we find a wealth of terminology related to energy and its many forms. Kinetic energy, potential energy, thermal energy, and electromagnetic energy are just a few of the ways in which this fundamental quantity can manifest. Vocabulary such as work, power, and efficiency allowphysicists to quantify and analyze the transformations of energy that drive so much of the physical universe.As we venture further into the specialized realms of physics, the vocabulary tree becomes increasingly intricate and technical. In the domain of waves and optics, terms like frequency, wavelength, and interference describe the undulating patterns of energy that permeate our world, from the visible spectrum of light to the invisible vibrations of sound. The language of electromagnetism, with its electric and magnetic fields, charges, and currents, provides the means to understand the fundamental forces that shape our technological landscape.Delving into the world of modern physics, the vocabulary tree becomes even more complex, branching out into the realms of quantum mechanics, relativity, and particle physics. Concepts like wave-particle duality, Heisenberg's uncertainty principle, and the curvature of spacetime introduce a whole new lexicon that captures the mind-bending nature of the very small and the very large. Particles such as electrons, protons, and neutrons, along with their more exotic subatomic counterparts, populate this intricate domain, each with their own unique properties and behaviors.Throughout this physical vocabulary tree, we find a remarkable synthesis of precision and poetry. Each term is carefully crafted toconvey a specific meaning, allowing physicists to communicate complex ideas with unparalleled clarity. Yet, within this technical language, there is a inherent beauty and elegance that reflects the underlying harmony of the physical world. From the elegance of Maxwell's equations to the sublime simplicity of E=mc^2, the vocabulary of physics is a testament to the human capacity for intellectual exploration and discovery.As we ascend this vocabulary tree, we gain a deeper appreciation for the richness and complexity of the physical sciences. Each branch, each leaf, represents a piece of the puzzle that helps us understand the fundamental nature of our universe. By mastering this specialized language, we unlock the door to a world of wonder and possibility, where the laws of nature can be understood, predicted, and ultimately harnessed to improve the human condition. The physical vocabulary tree is not merely a collection of terms, but a living, growing testament to our relentless pursuit of knowledge and our never-ending quest to unravel the mysteries of the cosmos.。

物理学家的生平英语作文

物理学家的生平英语作文English Answer:Isaac Newton was an English mathematician, physicist, astronomer, alchemist, theologian, and author who is widely recognized as one of the most influential scientists of all time and a key figure in the scientific revolution. He is best known for his discovery of the laws of motion and universal gravitation, but also made significant contributions to optics, mathematics, and natural philosophy.Newton was born in Woolsthorpe, Lincolnshire, England, on January 4, 1643 (Julian calendar; January 14, 1643 Gregorian calendar). His father, also named Isaac Newton, died three months before Newton was born. His mother, Hannah Ayscough, remarried when Newton was three, and he was raised by his maternal grandmother. Newton attended The King's School, Grantham, from 1655 to 1661, where he excelled in mathematics and natural philosophy.In 1661, Newton entered Trinity College, Cambridge, where he studied mathematics and physics. He graduated in 1665 with a Bachelor of Arts degree and was elected a Fellow of Trinity College in 1667. In 1669, he was appointed Lucasian Professor of Mathematics at Cambridge, a position he held until 1701.Newton's most important scientific work was done during the years 1665 to 1667, when he developed his laws of motion and universal gravitation. He also made significant contributions to optics, developing the reflecting telescope and studying the dispersion of light. In 1687, he published his Principia Mathematica, which is considered one of the most important scientific works ever written.In addition to his scientific work, Newton was also a devout Christian and a student of alchemy. He served as Warden of the Royal Mint from 1696 to 1727, and was President of the Royal Society from 1703 to 1727. He diedin London on March 20, 1727 (Julian calendar; March 31, 1727 Gregorian calendar) and was buried in WestminsterAbbey.中文回答：艾萨克·牛顿是一位英国数学家、物理学家、天文学家、炼金术士、神学家和作家，被广泛认为是所有时代最有影响力的科学家之一，也是科学革命的关键人物。

带电粒子和球体电场,英语口语作文

带电粒子和球体电场,英语口语作文Title: The Interplay of Charged Particles and Spherical Electric Fields.In the vast and intricate landscape of physics, the interaction between charged particles and electric fieldsis a fascinating and fundamental aspect. This intricate dance between positive and negative charges, and the resulting electric fields they generate, is crucial in understanding the behavior of matter and energy. Specifically, when we delve into the realm of spherical electric fields, the complexity and beauty of these interactions become even more apparent.Let us delve into the world of charged particles. These particles, whether electrons, protons, or ions, possess an electric charge that determines their interaction with other charged particles and electric fields. The charge can be positive or negative, and its magnitude is measured in Coulombs. Charged particles are constantly in motion,influenced by the electric forces acting upon them.A spherical electric field, on the other hand, is created when a charge is distributed uniformly over the surface of a sphere. This distribution generates anelectric field that radiates outward from the center of the sphere, resembling the spokes of a wheel. The strength of this field decreases as one moves away from the center, following an inverse square law.When charged particles encounter such a spherical electric field, their trajectory is altered. If theparticle is positively charged, it will be attracted towards the negative charge distribution on the sphere. Conversely, a negatively charged particle will be repelled by the negative charge on the sphere. The force acting on the particle is proportional to the charge on both the particle and the sphere, as well as the inverse square of the distance between them.This interaction becomes particularly interesting when considering the dynamics of charged particles within thefield. For instance, a positively charged particle approaching a negatively charged sphere will accelerate towards it, reaching a maximum speed as it nears the surface. However, as it passes the sphere, the force acting on it reverses direction, causing it to decelerate and then accelerate back towards the original direction. This oscillatory motion continues indefinitely, with theparticle oscillating back and forth between the sphere and infinity.On the other hand, a negatively charged particle approaching a negatively charged sphere will be repelled and move away from the sphere. Its speed will increase asit moves away, but eventually, the force acting on it will become too weak, and the particle will coast along a straight path.The implications of these interactions are profound. They play a crucial role in understanding the behavior of atoms, molecules, and even larger objects like planets and stars. For instance, the electrostatic forces between charged particles are responsible for the stability ofatomic structures and the bonds that hold molecules together. Similarly, the electric fields generated by charged bodies like planets and stars influence the motion of other objects in their vicinity.In conclusion, the interplay between charged particles and spherical electric fields is a fascinating and crucial aspect of physics. It underpins our understanding of the behavior of matter and energy at the fundamental level. As we continue to explore this intricate dance between charges and fields, we gain deeper insights into the secrets of the universe and the nature of reality itself.。

英文介绍物理学家的作文

英文介绍物理学家的作文Physics is a fascinating field that has been shaped by the minds of great scientists. One such luminary is Albert Einstein, known for his groundbreaking theory of relativity. His work revolutionized our understanding of space, time, and gravity.Einstein's famous equation, E=mc^2, succinctly captures the relationship between energy and mass, demonstrating that they are interchangeable. This principle has profound implications for our comprehension of the universe, from the smallest particles to the most distant stars.Another notable physicist is Isaac Newton, whose laws of motion laid the groundwork for classical mechanics. Hisapple-inspired insight about gravity has been a cornerstone of physics for centuries, explaining the motion of celestial bodies and everyday objects alike.The contributions of Marie Curie to the field of radioactivity cannot be understated. As a pioneering woman in science, she conducted groundbreaking research on radioactive elements, leading to the discovery of polonium and radium. Her work has had a lasting impact on both science and medicine.Stephen Hawking, with his work on black holes and the origins of the universe, brought cosmology into the publicconsciousness. His theories on the nature of space and time have expanded our knowledge of the cosmos and its beginning.These physicists, through their dedication and intellect, have not only advanced scientific knowledge but also inspired generations to question, explore, and marvel at the wonders of the physical world. Their legacies continue to inspire curiosity and innovation in the pursuit of understanding the universe.。

High Energy Colliders

a r X iv:physics /97216v2[physics.acc-p h]18Feb1997HIGH ENERGY COLLIDERS R.B.Palmer,J.C.Gallardo Center for Accelerator Physics Brookhaven National Laboratory Upton,NY 11973-5000,USA February 2,2008Abstract We consider the high energy physics advantages,disadvantages and luminosity requirements of hadron (pp ,p ¯p ),lepton (e +e −,µ+µ−)and photon-photon colliders.Technical problems in obtaining increased energy in each type of machine are presented.The machines relative size are also discussed.1Introduction Particle colliders are only the last evolution of a long history of devices used to study the violent collisions of particles on one another.Earlier versions used accelerated beams impinging on ﬁxed targets.Fig.1shows the equivalent beam energy of such machines,plotted versus the year of their introduction.The early data given was taken from the original plot by Livingston[1].For hadron,i.e.proton or proton-antiproton,machines (Fig.1a),it shows an increase from around 105eV with a rectiﬁer generator in 1930,to 1015eV at the Tevatron (atFermilab near Chicago)in 1988.This represents an increase of more than a factor of about 33per decade (the Livingston line,shown as the dash-line)over 6decades.By 2005we expect to have the Large Hadron Collider (at CERN,Switzerland)with an equivalent beam energy of 1017eV,which will almost exactly continue this trend.The1SSC,had we built it on schedule,would,by this extrapolation,havebeen a decade too early!The rise in energy of electron machines shown(Fig.1b)is slightly less dramatic;but,as we shall discuss below,the relative eﬀectivephysics energy of lepton machines is greater than for hadron machines,and thus the eﬀective energy gains for the two types of machine arecomparable.These astounding gains in energy(×1012)have been partly bought by greater expenditure:increasing from a few thousand dollars for therectiﬁer,to a few billion dollars for the LHC(×106).The other factor(×106)has come from new ideas.Linear e+e−,γ−γ,andµ+µ−colliders are new ideas that we hope will continue this trend,but itwill not be easy.Figure1:The Livingston Plots:Equivalent beam energy of colliders versus the year of their introduction;(a)for Hadron Machines and(b)for Lepton Machines.22Physics Considerations2.1General.Hadron-hadron colliders(pp or p¯p)generate interactions between the many constituents of the hadrons(gluons,quarks and antiquarks); the initial states are not deﬁned and most interactions occur at rela-tively low energy,generating a very large background of uninteresting events.The rate of the highest energy events is a little higher for antiproton-proton machines,because the antiproton contains valence antiquarks that can annihilate on the quarks in the proton.But this is a small eﬀect for colliders above a few TeV,when the interactions are dominated by interactions between quarks and antiquarks in their seas,and between the gluons.In either case the individual parton-parton interaction energies(the energies used for physics)are a rel-atively small fraction of the total center of mass energy.This is a disadvantage when compared with lepton machines.An advantage, however,is that allﬁnal states are accessible.In addition,as we saw in Figs.1,hadron machines have been available with higher energies than lepton devices,and,as a result,most initial discoveries in Ele-mentary Particle Physics have been made with hadron machines.In contrast,lepton-antilepton collider generate interactions be-tween the fundamental point-like constituents in their beams,the re-actions produced are relatively simple to understand,the full machine energies are available for physics and there is negligible background of low energy events.If the center of mass energy is set equal to the mass of a suitable state of interest,then there can be a large cross section in the s-channel,in which a single state is generated by the interac-tion.In this case,the mass and quantum numbers of the state are constrained by the initial beams.If the energy spread of the beams is suﬃciently narrow,then precision determination of masses and widths are possible.A gamma-gamma collider,like the lepton-antilepton machines, would have all the machine energy available for physics,and would have well deﬁned initial states,but these states would be diﬀerent from those with the lepton machines,and thus be complementary to them.For most purposes(technical considerations aside)e+e−andµ+µ−colliders would be equivalent.But in the particular case of s-channel Higgs boson production,the cross section,being proportional to the3mass squared,is more than40,000times greater for muons than elec-trons.When technical considerations are included,the situation is more complicated.Muon beams are harder to polarize and muon colliders will have much higher backgrounds from decay products of the muons.On the other hand muon collider interactions will require less radiative correction and will have less energy spread from beam-strahlung.Each type of collider has its own advantages and disadvantages for High Energy Physics:they would be complementary.2.2Required Luminosity for Lepton Collid-ers.In lepton machines the full center of mass of the leptons is available for theﬁnal state of interest and a“physics energy”E phy can be deﬁned that is equal to the total center of mass energy.E phy=E c of m(1)Since fundamental cross sections fall as the square of the center of mass energies involved,so,for a given rate of events,the luminosity of a collider must rise as the square of its energy.A reasonable target luminosity is one that would give10,000events per unit of R per year(the cross section for lepton pair production is one R,the total cross section is about20R,and somewhat energy dependent as new channels open up):L req.≈1034(cm−2s−1) E phy74The same studies have also concluded that a factor of 10in luminosityis worth about a factor of 2in eﬀective physics energy,this beingapproximately equivalent to:E phy (L )=E phy (L =L req .) L7(T eV ) 0.6 LMachine C of M EnergyLuminosity Physics Energy TeV cm −2s −1TeVIt must be emphasized that this eﬀective physics energy is not a welldeﬁned quantity.It should depend on the physics being studied.Theinitial discovery of a new quark,like the top,can be made with asigniﬁcantly lower “physics”energy than that given here.And thecapabilities of diﬀerent types of machines have intrinsic diﬀerences.The above analysis is useful only in making very broad comparisonsbetween machine types.3Hadron-Hadron Machines 3.1Luminosity.An antiproton-proton collider requires only one ring,compared withthe two needed for a proton-proton machine (the antiproton has theopposite charge to the proton and can thus rotate in the same magnetring in the opposite direction -protons going in opposite directionsrequire two rings with bending ﬁelds of the opposite sign),but the lu-minosity of an antiproton-proton collider is limited by the constraints5in antiproton production.A luminosity of at least1032cm−2s−1 is expected at the antiproton-proton Tevatron;and a luminosity of 1033cm−2s−1may be achievable,but the LHC,a proton-proton ma-chine,is planned to have a luminosity of1034cm−2s−1:an order of magnitude higher.Since the required luminosity rises with energy, proton-proton machines seem to be favored for future hadron collid-ers.The LHC and other future proton-proton machines might[2]be upgradable to1035cm−2s−1,but radiation damage to a detector would then be a severe problem.The60TeV Really Large Hadron Colliders (RLHC:high and lowﬁeld versions)discussed at Snowmass are being designed as proton-proton machines with luminosities of1034cm−2s−1 and it seems reasonable to assume that this is the highest practical value.3.2Size and Cost.The size of hadron-hadron machines is limited by theﬁeld of the mag-nets used in their arcs.A cost minimum is obtained when a balance is achieved between costs that are linear in length,and those that rise with magneticﬁeld.The optimumﬁeld will depend on the technolo-gies used both for the the linear components(tunnel,access,distri-bution,survey,position monitors,mountings,magnet ends,etc)and those of the magnets themselves,including the type of superconductor used.Theﬁrst hadron collider,the60GeV ISR at CERN,used conven-tional iron pole magnets at aﬁeld less than2T.The only current hadron collider,the2TeV Tevatron,at FNAL,uses NbTi supercon-ducting magnets at approximately4◦K giving a bendingﬁeld of about 4.5T.The14TeV Large Hadron Collider(LHC),under construction at CERN,plans to use the same material at1.8◦K yielding bending ﬁelds of about8.5T.Future colliders may use new materials allowing even higher mag-neticﬁelds.Model magnets have been made with Nb3Sn,and studies are underway on the use of high T c superconductor.Bi2Sr2Ca1Cu2O8 (BSCCO)material is currently available in useful lengths as powder-in-Ag tube processed tape.It has a higher critical temperature and ﬁeld than conventional superconductors,but,even at4◦K,its current density is less than Nb3Sn at allﬁelds below15T.It is thus unsuitable for most accelerator magnets.In contrast YBa2Cu3O7(YBCO)ma-6terial has a current density above that for Nb3Sn(4◦K),at allﬁeldsand temperatures below20◦K.But this material must be deposited onspecially treated metallic substrates and is not yet available in lengthsgreater than1m.It is reasonable to assume,however,that it will beavailable in useful lengths in the not too distant future.it mean forhadron colliders.Figure2:Relative costs of a collider as a function of its bending magnetic ﬁeld,for diﬀerent superconductors and operating temperatures.A parametric study was undertaken to learn what the use of suchmaterials might do for the cost of colliders.2-in-1cosine theta su-perconducting magnet cross sections(in which the two magnet coilsare circular in cross section,have a cosine theta current distributionsand are both enclosed in a single iron yoke)were calculated usingﬁxed criteria for margin,packing fraction,quench protection,sup-port andﬁeld return.Material costs were taken to be linear in theweights of superconductor,copper stabilizer,aluminum collars,iron7yoke and stainless steel support tube.The cryogenic costs were taken to be inversely proportional to the operating temperature,and linear in the outer surface area of the cold mass.Tunnel,access,vacuum, alignment,focusing,and diagnostic costs were taken to be linear with tunnel length.The relative values of the cost dependencies were scaled from LHC estimates.Results are shown in Fig.2.Costs were calculated assuming NbTi at(a)4◦K,and(b)1.8◦K,Nb3Sn at(c)4◦K and YBCO High T c at 20◦K(d)and(e).NbTi and Nb3Sn costs per unit weight were taken to be the same;YBCO was taken to be either equal to NbTi(in(d)), or4times NbTi(in(e)).It is seen that the optimumﬁeld moves from about6T for NbTi at4◦K to about12T for YBCO at20◦K;while the total cost falls by almost a factor of2.One may note that the optimized cost per unit length remains approximately constant.This might have been expected:at the cost minimum,the cost of linear andﬁeld dependent terms are matched, and the total remains about twice that of the linear terms.The above study assumes this particular type of magnet and may not be indicative of the optimization for radically diﬀerent designs.A group at FNAL[3]is considering an iron dominated,alternating gradient,continuous,single turn collider magnet design(Lowﬁeld RLHC).Itsﬁeld would be only2T and circumference very large(350 km for60TeV),but with its simplicity and with tunneling innovations, it is hoped to make its cost lower than the smaller highﬁeld designs. There are however greater problems in achieving high luminosity with such a machine than with the higherﬁeld designs.4Circular e+e−Machines4.1Luminosity.The luminosities of most circular electron-positron colliders have been between1031and1032cm−2s−1,CESR is fast approaching1033cm−2s−1 and machines are now being constructed with even higher values. Thus,at least in principle,luminosity does not seem to be a limi-tation(although it may be noted that the0.2TeV electron-positron collider LEP has a luminosity below the requirement of Eq.2).84.2Size and Cost.At energies below100MeV,using a reasonable bendingﬁeld,the size and cost of a circular electron machine is approximately proportional to its energy.But at higher energies,if the bendingﬁeld B is main-tained,the energy lost∆V turn to synchrotron radiation rises rapidly∆V turn∝E4m4(4)and soon becomes excessive(R is the radius of the ring).A cost minimum is then obtained when the cost of the ring is balanced by the cost of the rf needed to replace the synchrotron energy loss.If the ring cost is proportional to its circumference,and the rf is proportional to its voltage then the size and cost of an optimized machine rises as the square of its energy.The highest energy circular e+e−collider is the LEP at CERN which has a circumference of27km,and will achieve a maximum center of mass energy of ing the predicted scaling,a 0.5TeV circular collider would have to have a170km circumference, and would be very expensive.5e+e−Linear CollidersFor energies much above that of LEP(0.2TeV)it is probably imprac-tical to build a circular electron collider.The only possibility then is to build two electron linacs facing one another.Interactions occur at the center,and the electrons,after they have interacted,must be discarded.The size of such colliders is now dominated by the length of the two linacs and is inversely proportional to the average accel-erating gradient in those structures.In current proposals[4]using conventional rf,these lengths are far greater than the circumferences of hadron machines of the same beam energy,but as noted in section 2.3,the eﬀective physics energy of a lepton machine is higher than that of a hadron machine with the same beam energy,thus oﬀsetting some of this disadvantage.5.1Luminosity.The luminosity L of a linear collider can be written:L=1σxP beamwhereσx andσy are average beam spot sizes including any pinch eﬀects,and we takeσx to be much greater thanσy.E is the beam energy,P beam is the total beam power,and,in this case,n collisions=1. This can be expressed[8]as,L≈12r oαU(Υ)P beam1αNγEP beamσy U(Υ)∝E3.(9)It is this requirement that makes it hard to design very high energy linear colliders.High beam power demands high eﬃciencies and heavy wall power consumption.A smallσy requires tight tolerances,low beam emittances and strongﬁnal focus.And a small value of U(Υ)is hard to obtain because of its weak dependence onΥ(∝Υ−1/3).105.2Conventional RF.The gradients for structures have limits that are frequency dependent,but the real limit on accelerating gradients in these designs come froma trade oﬀbetween the cost of rf power against the cost of length.Theuse of high frequencies reduces the stored energy in the cavities,re-ducing the rf costs and allowing higher accelerating gradients:theoptimized gradients being roughly proportional to the frequency upto a limit of approximately250MeV/m at a frequency of the order of100GHz.One might thus conclude then that higher frequencies shouldalways be preferred.There are however counterbalancing considera-tions from the requirements of luminosity.Figure3:Dependence of some sensitive parameters of0.5TeV proposed linear colliders as a function of their rf frequencies.11Fig.3,using parameters from current0.5TeV linear collider pro-posals[4],plots some relevant parameters against the rf frequency. One sees that as the frequencies rise,•the required alignment tolerances get tighter;•the resolution of beam position monitors must also be better;and•despite these better alignments,the calculated emittance growth during acceleration is worse;and•the wall-power to beam-power eﬃciencies are also less.Thus while length and cost considerations may favor high frequencies, yet luminosity considerations would prefer lower frequencies.5.3Superconducting RF.If,however,the rf costs can be reduced,for instance when supercon-ducting cavities are used,then there will be no trade oﬀbetween rf power cost and length and higher gradients would lower the length and thus the cost.Unfortunately the gradients achievable in currently op-erating niobium superconducting cavities is lower than that planned in the higher frequency conventional rf colliders.Theoretically the limit is about40MV/m,but practically25MV/m is as high as seems pos-sible.Nb3Sn and high Tc materials may allow higherﬁeld gradients in the future.The removal of the requirements for very high peak rf power al-lows the choice of longer wavelengths(the TESLA collaboration is proposing23cm at1.3GHz)thus greatly relieving the emittance re-quirements and tolerances,for a given luminosity.At the current25MeV per meter gradients,the length and cost of a superconducting machine is probably higher than for the conven-tional rf designs.With greater luminosity more certain,its proponents can argue that it is worth the greater price.If,using new supercon-ductors,higher gradients become possible,thus reducing lengths and costs,then the advantages of a superconducting solution might be-come overwhelming.5.4At Higher Energies.At higher energies(as expected from Eq.9),obtaining the required luminosity gets harder.Fig.4shows the dependency of some example12machine parameters with energy.SLC is taken as the example at0.1 TeV,NLC parameters at0.5and1TeV,and5and10TeV examples are taken from a review paper by one of the authors[6].One sees that:•the assumed beam power rises approximately as E;•the vertical spot sizes fall approximately as E−2;•the vertical normalized emittances fall even faster:E−2.5;and •the momentum spread due to beamstrahlung has been allowed to rise.These trends are independent of the acceleration method,fre-quency,etc,and indicate that as the energy and required luminosity rise,so the required beam powers,eﬃciencies,emittances and toler-ances will all get harder to achieve.The use of higher frequencies or exotic technologies that would allow the gradient to rise,will,in general,make the achievement of the required luminosity even more diﬃcult.It may well prove impractical to construct linear electron-positron colliders,with adequate luminosity,at energies above a few TeV.6γ−γCollidersA gamma-gamma collider[9]would use opposing electron linacs,as in a linear electron collider,but just prior to the collision point,laser beams would be Compton backscattered oﬀthe electrons to generate photon beams that would collide at the IP instead of the electrons.If suitable geometries are used,the mean photon-photon energy could be 80%or more of that of the electrons,with a luminosity about1/10th.If the electron beams,after they have backscattered the photons, are deﬂected,then backgrounds from beamstrahlung can be elimi-nated.The constraint on N/σx in Eq.5is thus removed and one might hope that higher luminosities would now be possible by raising N and loweringσx.Unfortunately,to do this,one needs sources of bunches with larger numbers of electrons and smaller emittances,and one must ﬁnd ways to accelerate and focus such beams without excessive emit-tance growth.Conventional damping rings will have diﬃculty doing this[10].Exotic electron sources would be needed,and methods using lasers to generate[11]or cool[12]the electrons and positrons are under consideration.13Figure4:Dependence of some sensitive parameters on linear collider energy, with comparison of same parameters forµ+µ−colliders.Clearly,although gamma-gamma collisions can and should be made available at any future electron-positron linear collider,to add physicscapability,whether they can give higher luminosity for a given beampower is less clear.7µ+µ−Colliders7.1Advantages and DisadvantagesThe possibility of muon colliders was introduced by Skrinsky et al.[13]and Neuﬀer[14]and has been aggressively developed over the past two14years in a series of meetings and workshops[15,16,17,18,19].The main advantages of muons,as opposed to electrons,for a lepton collider are:•The synchrotron radiation,that forces high energy electron col-liders to be linear,is(see Eq.4)inversely proportional to the fourth power of mass:It is negligible in muon colliders.Thusa muon collider can be circular.In practice this means in canbe smaller.The linacs for the SLAC proposal for a0.5TeV Next Linear Collider would be20km long.The ring for a muon collider of the same energy would be only about1.3km circum-ference.•The luminosity of a muon collider is given by the same formula (Eq.5)as given above for an electron positron collider,but there are two signiﬁcant changes:1)The classical radius r o is now that for the muon and is200times smaller;and2)the number of collisions a bunch can make n collisions is no longer1,but is now limited only by the muon lifetime and becomes related to the average bendingﬁeld in the muon collider ring,withn collisions≈150B aveWith an averageﬁeld of6Tesla,n collisions≈900.These two eﬀects give muons an in principle luminosity advantage of more than105.As a result,for the same luminosity,the required beam power,spot sizes,emittances and energy spread are far less in µ+µ−colliders than in e+e−machines of the same energy.The comparison is made in Fig.4above.•The suppression of synchrotron radiation induced by the oppo-site bunch(beamstrahlung)allows the use of beams with lower momentum spread,and QED radiation is reduced.•s-channel Higgs production is enhanced by a factor of(mµ/m e)2≈40000.This combined with the lower momentum spreads would allow more precise determination of Higgs masses,widths and branching ratios.But there are problems with the use of muons:•Muons can be obtained from the decay of pions,made by higher energy protons impinging on a target.But in order to obtain enough muons,a high intensity proton source is required with very eﬃcient capture of the pions,and muons from their decay.15•The selection of fully polarized muons is inconsistent with the requirements for eﬃcient collection.Polarizations only up to 50%are practical,and some loss of luminosity is inevitable (e+e−machines can polarize the e−’s up to≈85%).•Because the muons are made with very large emittance,they must be cooled,and this must be done very rapidly because of their short lifetime.Conventional synchrotron,electron,or stochastic cooling is too slow.Ionization cooling[20]is the only clear possibility,but does not cool to very low emittances.•Because of their short lifetime,conventional synchrotron accel-eration would be too slow.Recirculating accelerators or pulsed synchrotrons must be used.•Because they decay while stored in the collider,muons radiate the ring and detector with decay electrons.Shielding is essential and backgrounds will be high.7.2Design StudiesA collaboration,lead by BNL,FNAL and LBNL,with contributions from18institutions has been studying a4TeV,high luminosity sce-nario and presented a Feasibility Study[19]to the1996Snowmass Workshop.The basic parameters of this machine are shown schemat-ically in Fig.5and given in Table 2.Fig.6shows a possible layout of such a machine.Table2also gives the parameters of a0.5TeV demonstration ma-chine based on the AGS as an injector.It is assumed that a demonstra-tion version based on upgrades of the FERMILAB,or CERN machines would also be possible.The main components of the4TeV collider would be:•A proton source with KAON[21]like parameters(30GeV,1014 protons per pulse,at15Hz).•A liquid metal target surrounded by a20T hybrid solenoid to make and capture pions.•A5T solenoidal channel to allow the pions to decay into muons, with rf cavities to,at the same time,decelerate the fast ones that comeﬁrst,while accelerating the slower ones that come later.Muons from pions in the100-500MeV range emerge in a 6m long bunch at150±30MeV.1617Figure6:Layout of the collider and accelerator rings.•A solenoidal snake and collimator to select the momentum,and thus the polarization,of the muons.•A sequence of20ionization cooling stages,each consisting of:a) energy loss material in a strong focusing environment for trans-verse cooling;b)linac reacceleration and c)lithium wedges in dispersive environments for cooling in momentum space.•A linac and/or recirculating linac pre-accelerator,followed by a sequence of pulsedﬁeld synchrotron accelerators using supercon-ducting linacs for rf.•An isochronous collider ring with locally corrected low beta(β=3 mm)insertion.7.3Status and Required R and DMuon Colliders are promising,but they are in a far less developed state than hadron or e+e−machines.No muon collider has ever been built.Much theoretical and experimental work will be needed be-18Table2:Parameters of Collider RingsBeam energy TeV2.25 Beamγ19,0002,400 Repetition rate Hz15 2.5 Proton driver energy GeV3024 Protons per pulse10141014 Muons per bunch2101241012 Bunches of each sign21 Beam power MW38.7 Norm.rms emit.ǫnπmm mrad5090 Bending Fields T99 Circumference Km8 1.3 Ave.Bending Fields T65 Eﬀective turns900800β∗at intersection mm38 rms bunch length mm38 rms I.P.beam sizeµm 2.817 Chromaticity2000-400040-80βmax km200-40010-20 Luminosity cm−2s−1103510338Comparison of MachinesIn Fig.7,the eﬀective physics energies(as deﬁned by Eq.3)of repre-sentative machines are plotted against their total tunnel lengths.Wenote:Figure7:Eﬀective physics energies of colliders as a function of their total length.•Hadrons Colliders:It is seen that the energies of machines risewith their size,and that this rise is faster than linear(E eﬀ∝L1.3).This extra rise is a reﬂection of the increases in bend-ing magneticﬁeld used,as new technologies and materials havebecome available.20•Circular Electron-Positron Colliders:The energies of these ma-chines rise approximately as the square root of their size,as ex-pected from the cost optimization discussed in section4above.•Linear Electron-Positron Colliders:The SLAC Linear Collider is the only existing machine of this type.One example of a proposed machine(the NLC)is plotted.The line drawn has the same slope as for the hadron machines and implies a similar rise in accelerating gradient,as technologies advance.•Muon-Muon Colliders:Only the4TeV collider,discussed above, and the0.5TeV demonstration machine have been plotted.The line drawn has the same slope as for the hadron machines.It is noted that the muon collider oﬀers the greatest energy per unit length.This is also apparent in Fig.8,in which the footprints of a number of proposed machines are given on the same scale.Figure8:Approximate sizes of some possible future colliders.219ConclusionsOur conclusions,with the caveat that they are indeed only our opin-ions,are:•The LHC is a well optimized and appropriate next step towards high eﬀective physics energy.•A Very Large Hadron Collider with energy greater than the SSC(e.g.60TeV c-of-m)and cost somewhat less than the SSC,maywell be possible with the use of high T c superconductors that may become available.•A“Next Linear Collider”is the only clean way to complement the LHC with a lepton machine,and the only way to do so soon.But it appears that even a0.5TeV collider may be more expensive than the LHC,has signiﬁcantly less eﬀective physics energy,and will be technically challenging.Obtaining the design luminosity may not be easy.•Extrapolating conventional rf e+e−linear colliders to energies above1or2TeV will be very diﬃcult.Raising the rf frequency can reduce length and probably cost for a given energy,but ob-taining luminosity increasing as the square of energy,as required, may not be feasible.•Laser driven accelerators are becoming more realistic and can be expected to have a signiﬁcantly lower cost per TeV.But the ratio of luminosity to wall power is likely to be signiﬁcantly worse than for conventional rf driven machines.Colliders using such tech-nologies are thus unlikely to achieve the very high luminosities needed for physics research at higher energies.•A higher gradient superconducting Linac collider using Nb3Sn or high T c materials,if it became technically possible,could be the most economical way to attain the required luminosities ina higher energy e+e−collider.•Gamma-gamma collisions can and should be obtained at any future electron-positron linear collider.They would add physics capability to such a machine,but,despite their freedom from the beamstrahlung constraint,may not achieve higher luminosity.•A Muon Collider,being circular,could be far smaller than a conventional rf e+e−linear collider of the same energy.Very pre-liminary estimates suggest that it would also be signiﬁcantly22。

北京中国人民大学附属中学高考英语二模试卷分类汇编阅读理解

北京中国人民大学附属中学高考英语二模试卷分类汇编阅读理解一、高中英语阅读理解1．（2019•北京）阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。

By the end of the century, if not sooner, the world's oceans will be bluer and greener thanks to a warming climate, according to a new study.At the heart of the phenomenon lie tiny marine microorganisms (海洋微生物) called phytoplankton. Because of the way light reflects off the organisms, these phytoplankton create colourful patterns at the ocean surface. Ocean colour varies from green to blue, depending on the type and concentration of phytoplankton. Climate change will fuel the growth of phytoplankton in some areas, while reducing it in other spots, leading to changes in the ocean's appearance.Phytoplankton live at the ocean surface, where they pull carbon dioxide (二氧化碳) into the ocean while giving off oxygen. When these organisms die, they bury carbon in the deep ocean, an important process that helps to regulate the global climate. But phytoplankton are vulnerable to the ocean's warming trend. Warming changes key characteristics of the ocean and can affect phytoplankton growth, since they need not only sunlight and carbon dioxide to grow, but also nutrients.Stephanie Dutkiewicz, a scientist in MIT's Center for Global Change Science, built a climate model that projects changes to the oceans throughout the century. In a world that warms up by 3℃, it found that multiple changes to the colour of the oceans would occur. The model projects that currently blue areas with little phytoplankton could become even bluer. But in some waters, such as those of the Arctic, a warming will make conditions riper for phytoplankton, and these areas will turn greener. "Not only are the quantities of phytoplankton in the ocean changing." she said, "but the type of phytoplankton is changing."（1）What are the first two paragraphs mainly about?A. The various patterns at the ocean surface.B. The cause of the changes in ocean colour.C. The way light reflects off marine organisms.D. The efforts to fuel the growth of phytoplankton.（2）What does the underlined word "vulnerable" in Paragraph 3 probably mean?A. SensitiveB. BeneficialC. SignificantD. Unnoticeable（3）What can we learn from the passage?A. Phytoplankton play a declining role in the marine ecosystem.B. Dutkiewicz's model aims to project phytoplankton changesC. Phytoplankton have been used to control global climateD. Oceans with more phytoplankton may appear greener.（4）What is the main purpose of the passage?A. To assess the consequences of ocean colour changesB. To analyse the composition of the ocean food chainC. To explain the effects of climate change on oceansD. To introduce a new method to study phytoplankton【答案】（1）B（2）A（3）D（4）C【解析】【分析】本文是一篇说明文，一项最新研究表明，由于气候变暖，世界海洋将会变得更蓝、更绿。

介绍一种科学现象的英语作文高中

介绍一种科学现象的英语作文高中全文共3篇示例，供读者参考篇1Title: Introduction to the Phenomenon of Quantum EntanglementIntroductionQuantum entanglement is a fascinating phenomenon in the field of quantum physics that has captivated the interest of scientists and researchers for decades. It is a concept that challenges our understanding of classical physics and has the potential to revolutionize the way we think about the nature of reality.Overview of Quantum EntanglementQuantum entanglement refers to a situation in which two or more particles become connected in such a way that the state of one particle influences the state of the other particle, regardless of their distance apart. This connection is not based on any direct interaction between the particles, but rather on a quantum property known as superposition. Superposition allows particlesto exist in multiple states simultaneously until they are measured, at which point they collapse into a single state.The phenomenon of quantum entanglement was first proposed by Albert Einstein, Podolsky, and Rosen (EPR) in 1935 as a means of highlighting what they perceived as a flaw in the theory of quantum mechanics. They argued that if quantum entanglement was real, it would imply the existence of non-local interactions that violated the principles of relativity. However, subsequent experiments conducted by John Bell in 1964 and others have since confirmed the reality of quantum entanglement, leading to its acceptance as a fundamental aspect of quantum mechanics.Applications of Quantum EntanglementQuantum entanglement has a wide range of potential applications in fields such as quantum computing, cryptography, and teleportation. In quantum computing, entangled particles can be used to perform calculations at speeds far beyond those achievable with classical computers. In quantum cryptography, entanglement can be used to create secure communication channels that are immune to eavesdropping. In quantum teleportation, entangled particles can be used to transfer thestate of one particle to another over long distances instantaneously.Challenges and LimitationsDespite its potential applications, quantum entanglement also poses several challenges and limitations. One of the main challenges is maintaining entanglement over long distances, as the fragile nature of entangled states makes them susceptible to decoherence and interference from external factors. Another challenge is the difficulty of creating and controlling entangled states with high precision, as this requires specialized equipment and expertise.Future PerspectivesLooking ahead, the study of quantum entanglement is likely to continue to advance our understanding of the fundamental nature of the universe. As researchers develop new techniques for creating and manipulating entangled states, we may see even more groundbreaking applications emerge in the fields of quantum technology and information science. Ultimately, the phenomenon of quantum entanglement holds the key to unlocking a new era of scientific discovery and technological innovation.ConclusionIn conclusion, quantum entanglement is a remarkable phenomenon that challenges our conventional understanding of the physical world. By exploring the intricate connections between entangled particles, scientists are uncovering new insights into the mysteries of quantum mechanics and paving the way for a future filled with endless possibilities. As we continue to unravel the secrets of quantum entanglement, we can look forward to a future driven by the power of quantum technology and the boundless potential it holds for shaping the world of tomorrow.篇2IntroductionScience is a fascinating field that helps us understand the world around us. One of the most interesting aspects of science is the study of various natural phenomena. These phenomena provide insights into how the world works and can help us make sense of the complex and intricate interactions that shape our environment. In this essay, we will explore the phenomenon of auroras, also known as the Northern and Southern Lights.Description of AurorasAuroras are stunning natural light displays that occur in the polar regions of the Earth. The phenomenon is caused by the interaction between the Earth's magnetic field and charged particles from the sun. These charged particles are released from the sun in the form of solar wind and are drawn towards the poles by the Earth's magnetic field.As the charged particles enter the Earth's atmosphere, they collide with gas molecules such as oxygen and nitrogen. These collisions produce bright, colorful lights that dance across the sky in patterns that vary in intensity and shape. The colors of the auroras depend on the type of gas molecules involved in the collisions. Oxygen molecules typically produce green and red auroras, while nitrogen molecules produce blue and purple hues.Auroras can be seen in both the Northern and Southern Hemispheres, with the Northern Lights (or Aurora Borealis) occurring near the North Pole and the Southern Lights (or Aurora Australis) occurring near the South Pole. The lights are most commonly observed during the winter months when the nights are long and dark.Scientific ExplanationThe phenomenon of auroras can be explained by the interactions between the Earth's magnetic field and the solarwind. The Earth's magnetic field acts as a protective shield, deflecting the charged particles from the sun away from the planet. However, the magnetic field is weaker at the poles, allowing some of the charged particles to enter the atmosphere.When the charged particles collide with gas molecules in the atmosphere, they transfer energy to the molecules, causing them to emit light. This process is similar to the way that fluorescent lights work, where electricity excites gas molecules to produce light. The different colors of the auroras are due to the specific wavelengths of light emitted by the excited gas molecules.The intensity of the auroras is also influenced by the strength of the solar wind and the Earth's magnetic field. During periods of high solar activity, such as solar storms or flares, the solar wind can be stronger, leading to more intense auroras. Likewise, disruptions in the Earth's magnetic field, such as geomagnetic storms, can also enhance the visibility of the lights.Impact of AurorasAuroras have fascinated people for centuries and have inspired myths, legends, and artwork. They are a reminder of the beauty and wonder of the natural world and serve as a reminder of the interconnectedness of the Earth and the sun. In addition totheir aesthetic appeal, auroras also play a role in scientific research.Scientists study auroras to better understand the dynamics of the Earth's atmosphere and the interactions between the Earth and the sun. By monitoring auroral activity, researchers can gain insights into solar activity, space weather, and the effects of magnetic storms on the Earth's environment. Auroras also serve as a visual reminder of the importance of safeguarding the Earth's magnetic field and protecting the planet from the harmful effects of solar radiation.ConclusionAuroras are a spectacular natural phenomenon that continues to captivate and intrigue scientists and laypeople alike. Their ethereal beauty and colorful displays offer a window into the complex interactions between the Earth and the sun, highlighting the interconnectedness of the natural world. By studying auroras, scientists can deepen our understanding of the Earth's atmosphere and the effects of solar activity on our planet. As we continue to explore and investigate the mysteries of the universe, auroras remain a shining example of the wonders of science and the natural world.篇3Title: Introduction to the Butterfly EffectIntroductionThe Butterfly Effect is a fascinating scientific phenomenon that demonstrates how small actions can have significant and far-reaching consequences. This principle, popularly known as the fluttering wings of a butterfly in Brazil setting off a tornado in Texas, is a key concept in chaos theory. In this essay, we will explore the origins of the Butterfly Effect, its implications in various fields of study, and how it affects our everyday lives.Origins of the Butterfly EffectThe concept of the Butterfly Effect was first introduced by Edward Lorenz, a mathematician and meteorologist, in the early 1960s. While running computer simulations to predict weather patterns, Lorenz discovered that even tiny variations in input values could lead to drastically different results. This realization led to the development of chaos theory, which focuses on the behavior of complex and dynamic systems.Implications in Various FieldsThe Butterfly Effect has profound implications in a wide range of fields, including meteorology, economics, psychology, and sociology. In meteorology, it highlights the inherent unpredictability of weather systems, as small changes in initial conditions can lead to drastically different outcomes. In economics, it has been used to explain market fluctuations and the ripple effects of economic decisions. In psychology and sociology, the Butterfly Effect underscores the interconnected nature of human behavior and how individual actions can have ripple effects on society as a whole.Everyday ApplicationAlthough the Butterfly Effect may seem like a highly abstract concept, it is actually quite relevant to our everyday lives. For example, a simple act of kindness towards a stranger can lead to a chain reaction of positivity, inspiring others to pay it forward. Similarly, a small mistake at work can snowball into a larger issue if left unaddressed. By being mindful of our actions and their potential consequences, we can harness the power of the Butterfly Effect to create positive change in our lives and the world around us.ConclusionIn conclusion, the Butterfly Effect is a thought-provoking concept that highlights the interconnectedness of the universe and the power of small actions. By understanding and embracing this principle, we can cultivate a greater sense of responsibility and mindfulness in our interactions with others and the world at large. As we navigate the complexities of modern life, let us remember the profound impact that even the smallest gesture can have, and strive to be the butterflies that set off positive and transformative change.。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

arXiv:hep-ph/9803480v1 27 Mar 1998
Abstract. Muon colliders oﬀer special opportunities to discover and study new physics. With the high intensity source of muons at the front end, orders of magnitude improvements would be realized in searches for rare muon processes, in deep inelastic muon and neutrino scattering experiments, and in long-baseline neutrino oscillation experiments. At a 100 to 500 GeV muon collider, neutral Higgs boson (or techni-particle) masses, widths and couplings could be precisely measured via s-channel production. ¯, Zh and supersymmetric particle Also, threshold cross-section studies of W + W − , tt pairs would precisely determine the corrresponding masses and test supersymmetric radiative corrections. At the high energy frontier a 3 to 4 TeV muon collider is ideally suited for the study of scalar supersymmetric particles and extra Z -bosons or strong W W scattering.
charm production (∼6% of the total cross section) and to measure sin2 θw (and infer the W -mass to an accuracy ∆MW ≃ 30–50 MeV in one year) [4].
∗
Invited talk presented at the 4th International Conference on the Physics Potential and Development of µ+ µ− Colliders, San Francisco, December 1997
The NMC will be particularly valuable for reconstructing supersymmetric particles of high mass from their complex cascade decay chains. Also, any Z ′ resonances within the kinematic reach of the machine would give enormous event rates. The eﬀects of virtual Z ′ states would be detectable to high mass. If no Higgs bosons exist below ∼1 TeV, then the NMC would be the ideal machine for the study of strong W W scattering at TeV energies. Plus, there are numerous other new physics possibilities for muon facilities that are beyond the scope of the present report [1]. In the following sections the physics opportunities above are discussed in greater detail. The work on physics at muon colliders reported in Sections III, VI and IX is largely based on collaborations with M.S. Berger, J.F. Gunion and T. Han.
II
FRONT END PHYSICS A Rare muon decays
The planned muon ﬂux ∼1014 muons/sec for a muon collider dramatically eclipses the ﬂux ∼108 muons/sec of present sources. With an intense source the rare muon processes µ → eγ (current branching fraction < 0.49×10−12 ), µN → eN conversion, and the muon electric dipole moment can be probed at very interesting levels. A generic prediction of supersymmetric grand uniﬁed theories is that these lepton ﬂavor violating or CP violating processes should occur via loops at signiﬁcant rates, e.g. BF(µ → eγ ) ∼ 10−13 [2]. Lepton ﬂavor violation can also occur via Z ′ bosons, lepton quarks, and heavy neutrinos [3].
University of Wisconsin - Madison
MADPH-98-1040 March 1998
Overview of Physics at ahysics Department, University of Wisconsin, Madison, WI 53706, USA
B
µp collider
The possibility of colliding 200 GeV muons with 1000 GeV protons at Fermilab is under study [4]. This collider would reach a maximum Q2 ∼ 8 × 104 GeV2 , which is ∼90 times the reach of the HERA ep collider, and deliver a luminosity ∼1033 cm−2 s−1 , which is ∼300 times the HERA luminosity. The µp collider would produce ∼106 neutral current deep inelastic scattering events per year at Q2 > 5000 GeV2 , which is over a factor 103 higher than at HERA. This µp collider would have a sensitivity to probe leptoquarks up to a mass MLQ ∼ 800 GeV and contact interactions to a scale Λ ∼ 6–9 TeV [5].
C
Neutrino ﬂux
Muon decays are the way to make neutrino beams of well deﬁned ﬂavors [4,6]. A muon collider would yield a neutrino ﬂux 1000 times that of the presently available neutrino ﬂux. Then ∼106 νN and ν ¯N events per year could be obtained to measure 2
I
INTRODUCTION
The agenda of physics at a muon collider falls into three categories: front end physics with a high-intensity muon source, First Muon Collider (FMC) physics at a machine with center-of-mass energies of 100 to 500 GeV, and Next Muon Collider (NMC) physics at 3–4 TeV center-of-mass energies. At the front end, a high-intensity muon source will permit searches for rare muon processes at branching sensitivities that are orders of magnitude below present upper limits. Also, a high-energy muon-proton collider can be constructed to probe high Q2 phenomena beyond the reach of the HERA ep collider. In addition, the decaying muons will provide high-intensity neutrino beams for precision neutrino cross-section measurements and for long-baseline experiments. The FMC will be a unique facility for neutral Higgs boson (or techni-resonance) studies through s-channel resonance production. Measurements can also be made − 0 0 ˜ +˜ − ¯, Zh, χ+ of the threshold cross sections for W + W − , tt ˜ν ˜ pro1 χ1 , χ2 χ1 , ℓ ℓ and ν duction that will determine the corresponding masses to high precision. Chargino, neutralino, slepton and sneutrino pair production cross section measurements would probe the loop corrections to gauge couplings in the supersymmetric sector. A µ+ µ− → Z 0 factory, utilizing the partial polarization of the muons, could allow signiﬁcant improvements in sin2 θw precision and in B -mixing and CP-violating studies.