The Baikal Neutrino Telescope Results, Plans, Lessons
医学物理实验_山东大学中国大学mooc课后章节答案期末考试题库2023年
医学物理实验_山东大学中国大学mooc课后章节答案期末考试题库2023年1.日常生活中的表面吸附现象有：The surface adsorption phenomena in dailylife are as follows:参考答案:面粉洗葡萄Washing grapes with flour_活性炭过滤水Activated carbonfilter water_水面上的油膜Oil film on water2.杨氏弹性模量E仅决定于材料本身的性质，而与外力ΔF，物体的长度L以及截面积S的大小无关，它是表征固体材料性质的一个重要物理量。
Young's modulus of elasticity e is only determined by the properties of thematerial itself, but has nothing to do with the external force Δ F, the length L of the object and the cross section product S. It is an important physicalquantity to characterize the properties of solid materials.参考答案:正确3.精密度是与“真值”之间的一致程度，是系统误差与随机误差的综合。
Precision is the degree of consistency with "true value", and is the synthesis of systematic error and random error.参考答案:错误4.以下说法正确的是：Which statement below is correct参考答案:在一定的温度下，它的旋光率与入射光波长的平方成反比，且随波长的减少而迅速增大，这现象称为旋光色散。
UPLC-MS
分析检测UPLC-MS/MS法检测草鱼中恩诺沙星残留量的不确定度评估李 娇1，罗景阳1，李巧莲1，王岩松1，陈 娇1，宣 彤2（1.沈阳市食品药品检验所，辽宁沈阳 110122；2.沈阳医学院公共卫生学院，辽宁沈阳 110034）摘 要：目的：评估超高效液相色谱-串联质谱（Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry，UPLC-MS/MS）法检测草鱼中恩诺沙星残留量的不确定度。
方法：依据《测量不确定度评定与表示（含第1号修改单）》（JJF 1059.1—2012）、《测量不确定度要求的实施指南》（CNAS-GL05—2011）、《化学分析中不确定度的评估指南》（CNAS-GL006：2019），对草肉中恩诺沙星的残留量进行不确定度评估分析。
结果：当草鱼中恩诺沙星的残留量为183 µg·kg-1时，其扩展不确定度为12 µg·kg-1 （k=2），不确定度主要来源于体积不确定度、UPLC-MS/MS仪器的不确定度。
结论：提高检验人员的实验操作能力，定期校准UPLC-MS/MS仪，可提高检测结果的准确性。
关键词：不确定度；恩诺沙星；超高效液相色谱-串联质谱（ UPLC-MS/MS）；草鱼Uncertainty Evaluation for the Determination of Enrofloxacin in Ctenopharyngodon idella by UPLC-MS/MSLI Jiao1, LUO Jingyang1, LI Qiaolian1, WANG Yansong1, CHEN Jiao1, XUAN Tong2(1.Shenyang Institute of Food and Drug Control, Shenyang 110122, China;2.School of Public Health, Shenyang Medical College, Shenyang 110034, China)Abstract: Objective: The uncertainty of measurement in determination of enrofloxacin in Ctenopharyngodon idella by UPLC-MS/MS is evaluated. Method: According to relevant standards such as JJF 1059.1—2012, CNAS-GL05—2011 and CNAS-GL006: 2019, the uncertainty for the determination of enrofloxacin in Ctenopharyngodon idella by UPLC-MS/MS was established. Result: When the content of enrofloxacin in Ctenopharyngodon idella was 183 µg·kg-1, the expanded uncertainty was 12 µg·kg-1 (k=2). The uncertainty mainly comes from volume uncertainty and UPLC-MS/MS instrument generated by the uncertainty. Conclusion: Improve the experimental operation ability of inspectors and regularly calibrate UPLC-MS/MS instrument to make it accurate.Keywords: uncertainty; enrofloxacin; ultra performance liquid chromatography-tandem mass spectrometry ( UPLC-MS/MS); Ctenopharyngodon idella测量不确定度在一定程度上反映了实验室检测结果的准确性和可靠性，检测结果的表述包括被测量的值及与该值相关的测量不确定度。
利用迈克耳逊干涉仪测气体折射率实验报告
利用迈克耳逊干涉仪测气体折射率实验报告英文回答：Introduction。
The Michelson interferometer is a device that can be used to measure the refractive index of a gas. It consists of two arms of equal length, each of which is terminated by a mirror. A beam of light is split into two beams, and each beam is sent down one of the arms. The beams are then reflected back by the mirrors and recombined. If the refractive index of the gas in one of the arms is different from the refractive index of the gas in the other arm, the beams will be out of phase when they are recombined, and this will produce an interference pattern.Procedure。
I set up the Michelson interferometer and aligned themirrors so that the beams were recombining in the center of the screen. I then introduced a sample of gas into one of the arms and observed the interference pattern. I measured the distance between the bright bands and used this to calculate the refractive index of the gas.Results。
Ultra- and extremely high energy neutrino astronomy
Underwater/ice neutrino telescopes (UNTs) represent a 3-D arrays of photomultipliers deployed deep in the lake, ocean or in the polar ice at the depth of 1 to 4 kilometers to provide with a shield against the sun and moon light background and background of atmospheric muons. Detection principle is based on registration of the Cherenkov photons emitted by charged leptons (including those emitted by secondaries produced along their way in the water or ice and by their decay products) which are generated in CC neutrino interactions νl N −C→C l X (see Fig. 1). Also hadronic showers produced in NC neutrino interactions νl N −N→C νl X inside UNT sensitive volume can be
MeV-range neutrino astronomy have been existing for forty years with two neutrino sources identified so far,
近十年对大脑的研究成果英文报告
近十年对大脑的研究成果英文报告The Mechanism of Processing Information by BrainI wrote this paper because I was curious about how the brain processed information that a man came across. The telencephalon contains the brain and the basal ganglia. Diencephalon includes thalamus and hypothalamus. Human brain is the most important part of the central nervous system, and also the most important part of information processing. This project will explore the mechanism of information processing in the brain.Scientific research has tested that the brain is split into cerebral hemisphere and right brain (Abbot, 2002). It has been studied that the event of left and right hemisphere is totally different, which means several secrets of human characteristics and abilities. Brain cells that perceive arithmetic and language are targeted within the cerebral hemisphere, whereas brain cells that play feeling and appreciate art are targeted within the right brain. individuals with a well-developed right brain are seemingly to be stronger in perception and imagination, likewise as in perception, special sense and also the ability to understand the general state of affairs. At constant time, they're additional agile in varied movements. the foremost vital contribution of the correct brain is ability. It doesn't stiffly adhere to the native analysis, however appearance at the general state of affairs, with boldness speculates andleaps forward to succeed in the intuitive conclusion. In some individuals, intuitive thinking has even become a form of second-sighted ability, sectionalize them to predict future changes and build vital choices before (Brzozowska, 2018).The right brain has a better memory than the left. It has an unforgettable poetic desire. If you deal with simple language problems, the brain is relatively active. The left brain is well developed. It is active in social occasions. It can evaluate different relationships and causal relationships. The left brain is well developed, statistically good and strong. That left brain is good. It's developed in organizations.Based on this week's experiment, I found that subjects respond more to color than words, so why does the brain process text information faster than image information? Generally, Human’s abilities to feel are called "five senses" (Braddick, et al, 2011). These five senses control the resonance between the autonomic nervous system and the outside world. It's about the subconscious. This is where the right brain processes the received information in the form of an image. Images can be processed immediately so that a large amount of information can be processed at the same time. This way of thinking includes mental calculation, shorthand and psychological activities. The characteristics of the right brain of ordinary people are controlled and suppressed by the rationality of the left brain, so it is difficult to show them. However,people who have the flexibility to use the right brain can identify colors by listening to sounds or by presenting pictures and smells. That is where the potential of the right brain comes from.I studied the process of sensory information processing as a breakthrough to reveal the mysteries of the brain, especially the visual system. Learnt from Cao (2017), the photoreceptor level of the retina was the second messenger of the photoelectric process, while the photoreceptor cells in the eye are depolarized. According to Tomizawa et al (2003), the final result of the two-dimensional and multi-level information processing of the retina is transmitted to the brain through the retinal ganglion cells in the form of action potential pulse frequency modulation. Moreover, the right brain is the image brain, which focuses on processing random, imaginative, intuitive and multi-sensory images (Tomizawa et al. 2003). I knew that the right brain was used to looking for information in images, so it ccould formally transform words into images. In the same way, I think that the right brain can transform numbers and formulas into images, or imagine odors as some kind of image. The right brain will see, hear and think of things, all into images for thinking and memory. When the right brain wants to remember something, it first converts them into images and takes them into the brain, just like a camera, frames the content into a picture in the brain. When you use it, the image in your mind will float in front of you. Thespeed of photographic memory in the right brain is much faster than that in the left brain. According to Peter et al (2016), this is because when processing information, the left brain processes the information into words, and the five senses need to be transferred into language, so it takes time. It proves my opinion that The right brain processes the information graphically, so it's very fast, just a few seconds.。
高斯朴素贝叶斯训练集精确度的英语
高斯朴素贝叶斯训练集精确度的英语Gaussian Naive Bayes (GNB) is a popular machine learning algorithm used for classification tasks. It is particularly well-suited for text classification, spam filtering, and recommendation systems. However, like any other machine learning algorithm, GNB's performance heavily relies on the quality of the training data. In this essay, we will delve into the factors that affect the training set accuracy of Gaussian Naive Bayes and explore potential solutions to improve its performance.One of the key factors that influence the training set accuracy of GNB is the quality and quantity of the training data. In order for the algorithm to make accurate predictions, it needs to be trained on a diverse and representative dataset. If the training set is too small or biased, the model may not generalize well to new, unseen data. This can result in low training set accuracy and poor performance in real-world applications. Therefore, it is crucial to ensure that the training data is comprehensive and well-balanced across different classes.Another factor that can impact the training set accuracy of GNB is the presence of irrelevant or noisy features in the dataset. When the input features contain irrelevant information or noise, it can hinder the algorithm's ability to identify meaningful patterns and make accurate predictions. To address this issue, feature selection and feature engineering techniques can be employed to filter out irrelevant features and enhance the discriminative power of the model. Byselecting the most informative features and transforming them appropriately, we can improve the training set accuracy of GNB.Furthermore, the assumption of feature independence in Gaussian Naive Bayes can also affect its training set accuracy. Although the 'naive' assumption of feature independence simplifies the model and makes it computationally efficient, it may not hold true in real-world datasets where features are often correlated. When features are not independent, it can lead to biased probability estimates and suboptimal performance. To mitigate this issue, techniques such as feature extraction and dimensionality reduction can be employed to decorrelate the input features and improve the training set accuracy of GNB.In addition to the aforementioned factors, the choice of hyperparameters and model tuning can also impact the training set accuracy of GNB. Hyperparameters such as the smoothing parameter (alpha) and the covariance type in the Gaussian distribution can significantly influence the model's performance. Therefore, it is important to carefully tune these hyperparameters through cross-validation andgrid search to optimize the training set accuracy of GNB. By selecting the appropriate hyperparameters, we can ensure that the model is well-calibrated and achieves high accuracy on the training set.Despite the challenges and limitations associated with GNB, there are several strategies that can be employed to improve its training set accuracy. By curating a high-quality training dataset, performing feature selection and engineering, addressing feature independence assumptions, and tuning model hyperparameters, we can enhance the performance of GNB and achieve higher training set accuracy. Furthermore, it is important to continuously evaluate and validate the model on unseen data to ensure that it generalizes well and performs robustly in real-world scenarios. By addressing these factors and adopting best practices in model training and evaluation, we can maximize the training set accuracy of Gaussian Naive Bayes and unleash its full potential in various applications.。
New Results in the Physics of Neutrino Oscillations
a r X i v :h e p -p h /9810329v 2 13 O c t 1998New Results in the Physics of Neutrino OscillationsMassimo Blasone ∗Blackett Laboratory,Imperial College,Prince Consort Road,London SW72BZ,U.K.andDipartimento di Fisica dell’Universit`a di SalernoI-84100Salerno,ItalyContents:1.Introduction2.Mixing of Fermion Fields3.Neutrino Oscillations:the Exact Formula4.Berry Phase for Oscillating Neutrinos5.Discussion and Conclusions1.IntroductionNeutrino mixing and oscillations [1]are among the most interesting topics of modern Particle Physics:at theoretical level,the understanding of the origin of the small masses of neutrinos and of the mixing among generations is still a puzzling problem [2].At experi-mental level,recent results [3]seem finally to confirm the existence of neutrino oscillations and (consequently)of non vanishing masses for these particles.However,since the pioneering work of Pontecorvo [4],who first pointed out the possibility of flavor oscillations for mixed massive neutrinos,a careful analysis of the structure of the Hilbert space for mixed particles was not carried out successfully [5,6].This was achieved only recently [7]and in the present paper I report about these re-sults.I show that a study of the mixing transformations in Quantum Field Theory (QFT),reveals a rich non-perturbative structure of the vacuum for the mixed fields.This fact has phenomenological consequences on neutrino oscillations:the oscillation formula turns out to have an additional oscillating piece and energy dependent amplitudes,in contrast with the usual (quantum mechanical)Pontecorvo formula,which is however recovered in the rel-ativistic limit.I also show how the concept of a topological (Berry)phase naturally enters the physics of neutrino oscillations [8].2.Mixing of Fermion FieldsIn order to discuss neutrino oscillations in QFT,I consider the following Lagrangian for two Dirac fields νe and νµ(omit space-time dependence for brevity)L =¯νe (i ∂−m e )νe +¯νµ(i ∂−m µ)νµ−m eµ(¯νe νµ+¯νµνe ),(1)which is sufficient to describe the single particle evolution of a mixed fermion1.Mixing arisewhen the above Lagrangian is diagonalized by means of the transformationsνe (x )=ν1(x )cos θ+ν2(x )sin θνµ(x )=−ν1(x )sin θ+ν2(x )cos θ,(2)where θis the mixing angle.νe and νµare neutrino fields with definite flavors.ν1while ν2are (free)neutrino fields with definite masses m 1and m 2,respectively.In terms of ν1and ν2,the above Lagrangian readsL =¯ν1(i ∂−m 1)ν1+¯ν2(i ∂−m 2)ν2.(3)with m e =m 1cos 2θ+m 2sin 2θ,m µ=m 1sin 2θ+m 2cos 2θ,m eµ=(m 2−m 1)sin θcos θ.The free fields ν1(x )and ν2(x )are written asνi (x )=1V k ,r u r k ,i e −iωk,i t αr k ,i +v r −k ,i e iωk,i t βr †−k ,i e i k ·x ,i =1,2.(4)with ωk,i =√√1Theinclusion of interaction terms in the Lagrangian eq.(1)does not alter the following discussion which is about the transformations eq.(2).For a discussion of three flavor mixing,see ref.[7].2The generator G θ(t )is given byG θ(t )=exp θ S +(t )−S −(t ).(8)S +(t )≡d 3x ν†1(x )ν2(x ),S −(t )≡d 3x ν†2(x )ν1(x ),(9)and is (at finite volume)an unitary operator:G −1θ(t )=G −θ(t )=G †θ(t ),preserving the canonical anticommutation relations.Eqs.(6),(7)follow from d 2dθ2ναµ=−ναµwith the initial conditions ναe |θ=0=να1,d dθναµ|θ=0=−να1.Note that G θis an element of SU (2).Indeed,if one introducesS 3≡12d 3x ν†1(x )ν1(x )+ν†2(x )ν2(x ) ,(11)then the su (2)algebra is closed:[S +,S −]=2S 3,[S 3,S ±]=±S ±,[S 0,S 3]=[S 0,S ±]=0.(12)The crucial point about the above generator is that it does not leave invariant the vacuum |0 1,2.Its action on it results in a new state,|0(t ) e,µ≡G −1θ(t )|0 1,2,(13)which is the flavor vacuum,i.e.the vacuum for the flavorfields.Let us define |0 e,µ≡|0(0) e,µand compute 1,2 0|0 e,µ.By writing |0 e,µ= k |0 k e,µ,we obtain [7]:1,2 0|0 e,µ=k1−sin 2θ|V k |2 2=e k ln (1−sin 2θ|V k |2)2,(14)where the function V k is defined in eq.(18).Note that |V k |2depends on k only through itsmodulus,takes values in the interval [0,1(2π)3d 3k ,in the infinite volume limit we obtainlimV →∞1,2 0|0 e,µ=lim V →∞eVLet us now look at the explicit form for theflavor annihilation operators.Without loss of generality,we can choose the reference frame such that k=(0,0,|k|).In this case the annihilation operators have the simple form2:αrk,e(t)=cosθαr k,1+sinθ U∗k(t)αr k,2+ǫr V k(t)βr†−k,2αrk,µ(t)=cosθαr k,2−sinθ U k(t)αr k,1−ǫr V k(t)βr†−k,1 (16)βr−k,e(t)=cosθβr−k,1+sinθ U∗k(t)βr−k,2−ǫr V k(t)αr†k,2βr−k,µ(t)=cosθβr−k,2−sinθ U k(t)βr−k,1+ǫr V k(t)αr†k,1whereǫr=(−1)r.Also,V k(t)=|V k|e i(ωk,2+ωk,1)t and U k(t)=|U k|e i(ωk,2−ωk,1)t,with|U k|≡u r†k,2u r k,1=v r†−k,1v r−k,2|V k|≡ǫr u r†k,1v r−k,2=−ǫr u r†k,2v r−k,1.(17) Explicitly,|U k|=ωk,1+m12 ωk,2+m22 1+|k|22ωk,1 12ωk,21(ωk,2+m2)−km1m2(see Fig.1).0.250.5020406080100|V k |2kFIG.1.The fermion condensation density |V k |2in function of |k |and for sample values of the parameters m 1and m 2.Solid line:m 1=1,m 2=100;Long-dashed line:m 1=10,m 2=100;Short-dashed line:m 1=10,m 2=1000.m 1m 2:in this limit the (quantum-mechanical)Pontecorvo state is recovered.If we now assume that the neutrino state at time t is given by |νe (t ) =e −iHt |νe ,we seethat it is not possible to compare directly this state with the one at time t =0given in eq.(22).The reason is that the flavor vacuum |0 e,µis not eigenstate of the free Hamiltonian H and it “rotates”under the action of the time evolution generator:one indeed finds lim V →∞e,µ 0|0(t ) e,µ=0.Thus at different times we have unitarily inequivalent flavor vacua and this implies that we cannot directly compare flavor states at different times.A way to circumvent this problem is to study the propagators for the mixed fields νe ,νµ[11].The crucial point is about how to compute these propagators:if one (naively)uses the vacuum |0 1,2,one gets an inconsistent result (cf.eq.(29)).Let us show this by considering the Feynman propagator for electron neutrinos,S ee (x,y )=1,2 0|T[νe (x )¯νe (y )]|0 1,2(23)where T denotes time e of (2)gives S ee in momentum representation as5S ee(k0,k)=cos2θk+m1k2−m22+iδ,(24)which is just the weighted sum of the two propagators for the freefieldsν1andν2.It coincides with the Feynman propagator obtained by resumming(to all orders)the perturbative series S ee=S e 1+m2eµSµS e+m4eµSµS e SµS e+... =S e 1−m2eµSµS e −1,(25) where the“bare”propagators are defined as S e/µ=(k−m e/µ+iδ)−1.The transition amplitude for an electron neutrino created byαr†k,e at time t=0goinginto the same particle at time t,is given byP r ee(k,t)=iu r†k,1e iωk,1t S>ee(k,t)γ0u r k,1,(26) where the spinors u1and v1form the basis in which thefieldνe is expanded(cf.eq.(6)). Here,S>ee denotes the unordered Green’s function(or Wightman function):iS>ee(t,x;0,y)= 1,2 0|νe(t,x)¯νe(0,y)|0 1,2.The explicit expression for S>ee(k,t)isS>ee(k,t)=−i r cos2θe−iωk,1t u r k,1¯u r k,1+sin2θe−iωk,2t u r k,2¯u r k,2 .(27) The amplitude eq.(26)is independent of the spin orientation and given byP ee(k,t)=cos2θ+sin2θ|U k|2e−i(ωk,2−ωk,1)t.(28) For different masses and for k=0,|U k|2is always<1(cf.eq.(18)).Notice also that |U k|2→1in the relativistic limit|k|≫√In mixed(k,t)representation,we have(for k=(0,0,|k|)):G ee(k0,k)=S ee(k0,k)+2πi sin2θ |V k|2(k+m2)δ(k2−m22)−|U k||V k| r ǫr u r k,2¯v r−k,2δ(k0−ω2)+ǫr v r−k,2¯u r k,2δ(k0+ω2) ,(31)Comparison of eq.(31)with eq.(24)shows that the difference between the full and the per-turbative propagators is in the imaginary part.I define the Wightman functions for an electron neutrino as iG>ee(t,x;0,y)=e,µ 0|νe(t,x)¯νe(0,y)|0 e,µ,and iG>µe(t,x;0,y)=e,µ 0|νµ(t,x)¯νe(0,y)|0 e,µ.These are con-veniently expressed in terms of anticommutators at different times asiG>ee(k,t)= r u r k,1¯u r k,1 αr k,e(t),αr†k,e e−iωk,1t+v r−k,1¯u r k,1 βr†−k,e(t),αr†k,e e iωk,1t ,(32) iG>µe(k,t)= r u r k,2¯u r k,1 αr k,µ(t),αr†k,e e−iωk,2t+v r−k,2¯u r k,1 βr†−k,µ(t),αr†k,e e iωk,2t .(33)Here and in the followingαr†k,e stands forαr†k,e(0).We now have four distinct transitionamplitudes,given by anticommutators offlavor operators at different times:P r ee(k,t)≡i u r†k,1e iωk,1t G>ee(k,t)γ0u r k,1= αr k,e(t),αr†k,e=cos2θ+sin2θ |U k|2e−i(ωk,2−ωk,1)t+|V k|2e i(ωk,2+ωk,1)t ,(34) P r¯e e(k,t)≡i v r†−k,1e−iωk,1t G>ee(k,t)γ0u r k,1= βr†−k,e(t),αr†k,e=ǫr|U k||V k|sin2θ e i(ωk,2−ωk,1)t−e−i(ωk,2+ωk,1)t ,(35) P rµe(k,t)≡i u r†k,2e iωk,2t G>µe(k,t)γ0u r k,1= αr k,µ(t),αr†k,e=|U k|cosθsinθ 1−e i(ωk,2−ωk,1)t ,(36) P r¯µe(k,t)≡i v r†−k,2e−iωk,2t G>µe(k,t)γ0u r k,1= βr†−k,µ(t),αr†k,e=ǫr|V k|cosθsinθ 1−e−i(ωk,2+ωk,1)t .(37) All other anticommutators withα†e vanish.The probability amplitude is now correctly normalized:lim t→0+P ee(k,t)=1,and P¯e e,Pµe,P¯µe go to zero in the same limit t→0+. Moreover,|P r ee(k,t)|2+|P r¯e e(k,t)|2+ P rµe(k,t) 2+ P r¯µe(k,t) 2=1,(38) as the conservation of the total probability requires.We also note that these transition probabilities are independent of the spin orientation.In order to understand the above transition amplitudes,consider theflavor charge oper-ators,defined as Q e/µ≡ k,r(αr†k,e/µαr k,e/µ−βr†−k,e/µβr−k,e/µ).We then have:7e,µ 0(t)|Q e|0(t) e,µ=e,µ 0(t)|Qµ|0(t) e,µ=0,(39)νe(t)|Q e|νe(t) = αr k,e(t),αr†k,e 2+ βr†−k,e(t),αr†k,e 2,(40)νe(t)|Qµ|νe(t) = αr k,µ(t),αr†k,e 2+ βr†−k,µ(t),αr†k,e 2.(41) Charge conservation is ensured at any time: νe(t)|(Q e+Qµ)|νe(t) =1and the oscillation formula readily follows as(k,t)= αr k,e(t),αr†k,e 2+ βr†−k,e(t),αr†k,e 2(42) Pνe→νe=1−sin2(2θ) |U k|2sin2 ωk,2−ωk,12t ,(k,t)= αr k,µ(t),αr†k,e 2+ βr†−k,µ(t),αr†k,e 2(43) Pνe→νµ=sin2(2θ) |U k|2sin2 ωk,2−ωk,12t .This result is exact.There are two differences with respect to the usual formula for neutrino oscillations:the amplitudes are energy dependent,and there is an additional os-cillating term.For|k|≫√:ω2−ω1|νe(T) =e iφ|νe(0) ,φ=−2πω12πω2−ω1+We thus see that there is indeed a non-zero geometrical phaseβ,related to the mixing angle θ,and that it is independent from the neutrino energiesω1,ω2and masses m1,m2.An alternative way for calculating the geometrical phase is the following.Define the state|˜νe(t) ≡e−if(t)|νe(t) ,(47) with f(t)=−ω1t such that f(T)−f(0)=φ.Then the Berry phase is defined as:β= T0 ˜νe(t)|i dREFERENCES[1]R.Mohapatra and P.Pal,Massive Neutrinos in Physics and Astrophysics,(World Scien-tific,Singapore,1991);J.N.Bahcall,Neutrino Astrophysics,(Cambridge Univ.Press,Cambridge,1989). [2]H.Fritzsch and Z.Z.Xing,hep-ph/9808272;H.Fritzsch and Z.Z.Xing,Phys.Rev.D57(1998)594;Phys.Lett.B413(1997)396.[3]Super-Kamiokande Collaboration(Y.Fukuda et al.).Phys.Rev.Lett.81(1998)1562;Kamiokande Collaboration(S.Hatakeyama et al.),Phys.Rev.Lett.81(1998)2016.[4]S.M.Bilenky and B.Pontecorvo,Phys.Rep.41(1978)225.[5]T.Kaneko,Y.Ohnuki and K.Watanabe,Prog.Theor.Phys.30(1963)521;K.Fujii,Il Nuovo Cimento34(1964)722;K.Fujii,C.Habe and T.Yabuki,hep-ph/9807266.[6]C.Giunti,C.W.Kim,J.A.Lee and U.W.Lee,Phys.Rev.D48(1993)4310;J.Rich,Phys.Rev.D48(1993)4318;E.Sassaroli,hep-ph/9710239;hep-ph/9609476.[7]M.Blasone and G.Vitiello,Ann.Phys.(N.Y.)244(1995)283;Erratum,ibid.249(1996)363;E.Alfinito,M.Blasone,A.Iorio and G.Vitiello,Phys.Lett.B362(1995)91.[8]M.Blasone,P.A.Henning and G.Vitiello,in preparation.[9]A.Perelomov,Generalized Coherent States and Their Applications,(Springer-Verlag,Berlin,1986).[10]J.Bardeen,L.Cooper and J.Schrieffer,Phys.Rev.108(1957)1175.[11]M.Blasone,P.A.Henning and G.Vitiello,hep-th/9803157.[12]M.V.Berry,Proc.Roy.Soc.London A392(1984)45.[13]Y.Aharonov and J.Anandan,Phys.Rev.Lett.58(1987)1593.[14]A.G.Wagh et al.,Phys.Rev.Lett.78(1997)755.[15]C.Itzykson and J.B.Zuber,Quantum Field Theory,(McGraw-Hill,New York,1980);H.Umezawa,Advanced Field Theory:Micro,Macro and Thermal Physics(AmericanInstitute of Physics,1993).[16]M.Blasone,PhD Thesis,Salerno University,December1996.10。
分析视力下降和提建议的英语作文
Analyzing Vision Decline and ProvidingSolutionsIn recent years, the issue of declining vision among individuals, especially among the younger population, has become a pressing concern. The alarming rise in this trend can be attributed to several factors, including prolonged exposure to screens, unhealthy lifestyle choices, and alack of awareness regarding eye care.The primary culprit behind this vision decline is the excessive use of electronic devices. With the advent of smartphones, tablets, and computers, people are spending more time than ever before staring at screens. Thisconstant strain on the eyes leads to fatigue and, over time, can result in permanent damage to vision. Additionally, the blue light emitted from these screens is harmful to the retina and can contribute to vision loss.Another significant factor is the sedentary lifestyle that many individuals adopt. Lack of physical activity anda diet rich in fruits and vegetables can lead to a decrease in blood circulation, affecting the health of the eyes.Additionally, smoking and excessive alcohol consumption are also known to negatively impact vision.Moreover, many people fail to prioritize eye care. Regular eye exams are crucial for detecting and treating vision problems early on. However, many individuals neglect this aspect of their health, often due to a lack of awareness or a busy schedule.To address this issue, several solutions can be implemented. Firstly, individuals should take measures to reduce their screen time. This can be achieved by setting limits on device usage, taking frequent breaks, and practicing eye exercises. Additionally, using blue light filters on electronic devices can help mitigate the harmful effects of blue light.Secondly, promoting a healthy lifestyle is essential. Regular exercise, a balanced diet, and avoiding smoking and excessive alcohol consumption can help maintain good eye health. Incorporating foods rich in vitamins A, C, and E, as well as omega-3 fatty acids, into the diet can further benefit eye health.Lastly, it is crucial to raise awareness about eye care. People should be educated about the importance of regular eye exams and the early detection of vision problems. Healthcare providers and educational institutions can playa pivotal role in this effort by including eye health education in their programs.In conclusion, the decline in vision is a multifaceted issue that requires a combined effort from individuals, healthcare providers, and society at large. By addressingthe underlying causes and implementing practical solutions, we can hope to reverse this trend and preserve the visionof future generations.**分析视力下降及提出建议**近年来，尤其是年轻人中视力下降的问题日益严重，这引起了人们的广泛关注。
Neutrino Event Rates from Gamma Ray Bursts
a rXiv:as tr o-ph/998138v38Oct1999University of Wisconsin -Madison MADPH-99-1134astro-ph/9908138August 1999Neutrino Event Rates from Gamma Ray Bursts F.Halzen and D.W.Hooper Department of Physics,University of Wisconsin,Madison,WI 53706Received August 13,1999;accepted October 7,1999ABSTRACTWe recalculate the diffuseflux of high energy neutrinos produced by Gamma Ray Bursts(GRB)in the relativisticfireball model.Although we confirm that the average single burst produces only∼10−2high energy neutrino events in a detector with1km2effective area,i.e.about10events per year,we show that the observed rate is dominated by burst-to-burstfluctuations which are very large.Wefind event rates that are expected to be larger by one order of magnitude,likely more,which are dominated by a few very bright bursts.This greatly simplifies their detection.Subject headings:gamma rays:bursts1.High Energy Neutrinos from Relativistic FireballsThe evidence has been steadily accumulating that GRB emission is the result of a relativistically expandingfireball energized by a process involving neutron stars or black holes(Piran1999).In the early stage,thefireball cannot emit efficiently because the radiation is trapped due to the very large optical depth.Thefireball’s energy is dissipated in kinetic energy until it becomes optically thin and produces the observed display.This scenario can accommodate the observed energy-and time scales provided the bulk Lorentz factorγof the expanding shock is∼300.The production of high energy neutrinos is anticipated:protons,accelerated in the kinetic phase of the shock,interact with photons producing charged pions which are the parents of neutrinos(Waxman&Bahcall1997).Standard particle physics andfireball phenomenology are sufficient to compute the neutrinoflux(Waxman&Bahcall1997; Halzen1998)as well as the observed rates in high energy neutrino telescopes.The observation of GRB neutrinos over a cosmological baseline has scientific potential beyond testing the“best-buy”fireball model:the observations can test with unmatched precision special relativity and the equivalence principle,and study oscillating neutrinoflavors over the ultimate baseline of z≃1.The anticipated neutrinoflux traces the broken power-law spectrum observed for the photons,which provide the target material for neutrino production:Aφ=for E>E B,(2)E2where A is a normalization constant which is determined from energy considerations andE B≈700TeV(Halzen1998).The total energy in GRB neutrinos is given byF tot=c2fπt hubble˙ρE,(3)where fπis the fraction of proton energy that goes into pion production,t hubble is10Byrs and˙ρE is the injection rate into protons accelerated to high energies in the kineticfireball. This is a critical parameter in the calculations;it can befixed,for instance,by assuming that GRB are the source of the highest energy cosmic rays beyond the ankle(Waxman 1995;Milgrom&Usov1995;Vietri1995)in the spectrum,or˙ρE≃4×1044erg Mpc−3yr−1 (Halzen1998).The factor fπrepresent the fraction of total energy going into pion production.It is calculated by known particle physics and is of order15%(Waxman& Bahcall1997;Halzen1998).We remind the reader that these assumptions reproduce the observed average photon energy per burst if equal energy goes into the hadronic and electromagnetic component of thefireball(Waxman&Bahcall1997).Now,normalizing theflux for this total energy:F tot=AE.(4)Approximating E B−E min≃E B,the integration constant is found to be1.20×10−12TeV cm−2s−1sr−1.The quantities fπand E B are calculated using Eqs.(4) and(5)in Waxman and Bahcall(1997).The GRB parameters entering these equations are chosen following Halzen(1998)and assumed to be independent ofγ.We assumedE max=107TeV.Given the neutrinofluxφ,the event rates in a neutrino detector are obtained by a straightforward method(Halzen1998):N= φ(E)Pν→µdE,(5) where Pν→µis the detection probability for neutrinos of muonflavor.It is determined,as a function of energy,by the neutrino cross sections and the range of the secondary muon(Gaisser,Halzen&Stanev1995;Gandhi et al.1996).We obtain an observed neutrinoflux of order10yr−1km−2assuming103bursts per year.This result is somewhat lower but not inconsistent with those obtained previously.One should keep in mind that neutrinos can also be produced,possibly with higher fluxes,in other stages of thefireball,e.g.when it expands through the interstellar medium (Katz1994;Halzen&Jaczko1996;Vietri1998;Boettcher&Dermer1998).2.Burst-to-Burst FluctuationsWe here want to draw attention to the fact that this result should not be used without consideration of the burst-to-burstfluctuations which are very large indeed;see also Dermer,Boettcher&Chiang(1999).We will,in fact,conclude that from an observational point of view the relevant rates are determined by thefluctuations,and not by the average burst.Our calculations are performed byfluctuating individual bursts according to the model described above with i)the square of the distance which is assumed to follow a Euclidean or cosmological distribution,ii)with the energy assuming that the neutrino rate depends linearly on energy and follows a simple step function with ten percent of GRB producing more energy than average by a factor of ten,and one percent by a factor of100, and,most importantly,iii)fluctuations in theγfactor around its average value of300. Thefluctuations inγaffect the value of fπwhich varies approximately asγ−4(Waxman& Bahcall1997)as well as the position of the break energy which varies asγ2.For a detailed discussion see Halzen(1998).Both effects are taken into account.Clearly a factor of ten variation ofγleads to a change influx by roughly4orders of magnitude.The origin of the largefluctuations withγshould be a general property of boosted accelerators.With high luminosities emitted over short times,the large photon densityrenders the GRB opaque unlessγis very large.Only transparent sources with large boost factors emit photons.They are however relatively weak neutrino sources because the actual photon target density in thefireball is diluted by the large Lorentz factor.This raises the unanswered question whether there are bursts with lowerγ-factors. Because of absorption such sources would emit less photons of lower energy and could have been missed by selection effects;they would be spectacular neutrino sources.Some have argued(Stern1999)for γ ∼30on the basis that the unusualfluctuations in the morphology of GRB can only be produced in a relatively dense,turbulent medium.3.Monte Carlo Simulation ResultsWe will illustrate the effect offluctuations by Monte Carlo simulation of GRB.For a Euclidean distribution the calculation can be performed analytically;in other cases the Monte Carlo method evaluates the integrals.The overwhelming effect offluctuations is demonstrated in sample results shown in Figs.1–3and Table1,a–c.Not knowing the distribution ofγ-factors around its average,we have parametrized it as a Gaussian with widthsσ,σ′below and above the average value of300.We choseσ′to be either0or300, to illustrate the effect of allowing GRB with Lorentz factors up to103with a Gaussian probability.The critical,and unknown,parameter isσ.It may,in fact,be more important than any other parameter entering the calculation.As far as we know,neither theory nor experiment provide compelling information at this point.Note that we requireσ>70in order to allow a significant part of the bursts to haveγ-factors less than102,or one third the average value;see Table1.The value ofσ′is less critical.A value of300allows for Lorentz factors as large as103.The dominant effect of this is a renormalization of the neutrino rates because a fraction of the bursts now have a largeγ-factor and,as a consequence,a low neutrinoflux.We discuss some quantitative examples next.Firstly,even in the absence of the dominantfluctuations inγ,the rate of9detected neutrinos per year over103bursts,becomes30–90in the presence offluctuations in energy and distance.The range covers a variety of assumptions for GRB distributions,which range from Euclidean to cosmological;the issue is not important here because other factors dominate thefluctuations.Every2years there will be an event with7neutrinos in a single burst.Forσ=70,the rate is∼600per year in a kilometer square detector,with23 individual bursts yielding more than4neutrinos and7yielding more than10in a single year!The results for other values ofσare tabulated in Table1.The number of events per year for a range of values ofσis shown in Fig.1.The frequency of GRB producing seven or more neutrinos is shown in Fig.2.The neutrino multiplicity of bursts forσ=30,60 and75is shown in Fig.3.Note that absorption in the source eventually reduces the overall rates whenγis much smaller than average,orσlarger than60.This factor is included in our calculations(Halzen1998).To this point we have assumed that all quantitiesfluctuate independently.Interestingly, the value ofσ=70is obtained in the scenario where insteadfluctuations inγare a consequence offluctuations in energy.In order not to double count,fluctuations in energy itself,which only contribute a factor of3to the neutrino rate anyway,should be omitted.Even though bursts with somewhat lowerγproduce neutrinos with reduced energy, compared to700TeV,over a longer time-scale than1second,the signatures of these models are spectacular.Existing detectors with effective area at the1–10%of a kilometer squared, should produce results relevant to the open question on the distribution of bulk Lorentz factors in thefireball model.Independent of the numerics,the fact that a single GRB with high energy,close proximity and a relatively low Lorentz factor can reasonably produce more detectable neutrino events than all other GRB over several years time,renders the result of thestraightforward diffuseflux calculation observationally misleading.Our calculations suggest that it is far more likely that neutrino detectors detect one GRB with favorable characteristics,than hundreds with average values.Clearly,our observations are relevant for other GRB models,as well as for blazars and any other boosted sources.They are also applicable to photons and may represent the underlying mechanism for the fact that the TeV extra-galactic sky consists of a few bursting sources.We expect no direct correlation between neutrino and high energy gamma sources because cosmic events with abundant neutrino production are almost certainly opaque to high energy photons.4.ConclusionsAlthough the average event rates predicted with typical GRB parameters appear somewhat discouraging to present and future Cerenkov neutrino detector experiments, thefluctuations in these calculations are more significant and affect the prospects for detection.We speculated on the distribution of the parameters entering thefireball model calculation and used a Monte Carlo simulation to estimate the actual event rates.The result of these simulations show that a kilometer scale detector could be expected to observe tens or hundreds of events per year.To improve on the reliability of this estimate,a well defined distribution for the Lorentz factor must be determined.Contrariwise,not observing neutrino GRB after years of observation will result in a strong limit on the number of accelerated protons in the kinetic phase of the burst,or infine-tuned,high values of the Lorentz boost factor.AcknowledgementsThis research was supported in part by the U.S.Department of Energy under Grant No.DE-FG02-95ER40896and in part by the University of Wisconsin Research Committee with funds granted by the Wisconsin Alumni Research Foundation.We thank G.Barouch, T.Piran and E.Waxman for discussions.REFERENCESBoettcher,M&Dermer,C.D.1998,astro-ph/9801027,ApJ,499,L131Dermer,C.D.,Boettcher,M.&Chiang,J.1999,ApJ Lett,in pressFor a review,see Gaisser,T.K.,Halzen,F.&Stanev,T.1995,Phys.Rep.,258(3),173 Gandhi,R.,Quigg,C.,Reno,M.H.&Sarcevic,I.1996,Astropart.Phys.,5,81 Halzen,F.1998,astro-ph/9810368,Lectures on Neutrino Astronomy:Theory and Experiment,given at the Theoretical Advanced Study Institute in ElementaryParticle Physics(TASI98),“Neutrinos in Physics and Astrophysics:From10−33to 10+28cm”,Boulder,Colorado,May31–June261998Halzen,F.&Jaczko,G.1996,Phys.Rev.D,54,2774Katz,J.I.1994,ApJ,432,L27Milgrom,M.&Usov,V.1995,ApJ,449,L37For a recent review,see Piran,T.1999,astro-ph/9810256,Phys.Rep.,314,575Stern,B.1999,astro-ph/9902203,in“High Energy Processes in Accreting Black Holes”,ed.J.Poutanen and R.Svensson(ASP Conf.Series),Vol.161,277Vietri,M.1995,ApJ,453,883Vietri,M.1998,Phys.Rev.Lett.80,3690Waxman,E.1995,Phys.Rev.Lett.,75,386Waxman,E.&Bahcall,J.N.1997,Phys.Rev.Lett.,78,2292Fig. 1.—Rate of high energy neutrino events in a detector with1km2effective area as a function of the range of the bulk Lorentz factorγ.The range is assumed to be Gaussian with widthσbelow the average of300,andσ′above.The latter is taken to be either0,or300.Fig. 2.—Yearly rate of individual neutrino bursts with more than7events in a detector with1km2effective area as a function of the range of the bulk Lorentz factorγ.The range is assumed to be Gaussian with widthσbelow the average of300,andσ′above.The latter is taken to be either0,or300.Fig. 3.—Neutrino multiplicity distribution in individual GRB in a detector with1km2 effective area.The range of the bulk Lorentz factorγis assumed to be Gaussian with width σ=30,60and75below the average of300,andσ′taken to be0.Table1:High energy neutrino events in a detector with1km2effective area as a function of the range of the bulk Lorentz factorγ.The range is assumed to be Gaussian with widthσbelow the average of300,andσ′above.The latter is taken to be either0,or300.Shown as a function ofσis the total number of neutrinos,as well as the yearly number of individual bursts with more than4,7,and11high energy neutrinos.For comparison,the middle line shows the result when allfluctuations are removed.σ′=0800.040.15 1.0919.8378.91276331812750.010.080.6817.481.88142715107000.040.3914.884.8611231276500.020.2012.187.74831810660000.099.4690.5394168455000.04 6.8693.1326136350000.01 4.5295.5271115245000 2.6297.422794240000 1.2898.7193832350000.4499.616773130000099.9146621000001008610.50.2Result if energy and distance are not allowed to vary:Percent of Lorentz Factors by Range GRB≥X Events/yrσ0–1010–5050–100100–200200–300Events/yr≥4≥7≥11。
The Baikal Neutrino Telescope Physics Results and Future Plans贝加尔湖中微子望远镜物理结果与未来计划
- Prompt muons and neutrinos - Exotic HE muons
Search for exotic particles
- Magnetic monopoles
Atmospheric Neutrinos
372 Neutrinos in 1038 Days (1998-2003)
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NT200 (1038 days)
DIFFUSE NEUTRgI=N1.O5 FLUX
(Ф ~ E-2, 10 TeV < E < 104 T2eV)
➢ Nizhny Novgorod State Technical University, Russia.
➢ St.Petersburg State Marine University, Russia.
➢ Kurchatov Institute, Moscow, Russia.
BAIKAL in CernCourier 7/8-2005
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Baikal
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Gamma-ray and neutrino emission from misaligned microquasars
a r X i v :a s t r o -p h /0505287v 1 13 M a y 2005Astronomy &Astrophysics manuscript no.2664February 2,2008(DOI:will be inserted by hand later)Gamma-ray and neutrino emission from misaligned microquasarsGustavo E.Romero 1,2,⋆and Mariana Orellana 1,2,⋆⋆1Instituto Argentino de Radioastronom ´ıa,C.C.5,(1894)Villa Elisa,Buenos Aires,Argentina 2Facultad de Ciencias Astron´o micas y Geof ´ısicas,Universidad Nacional de La Plata,Paseo del Bosque,1900La Plata,ArgentinaReceived /AcceptedAbstract.Microquasars are accreting X-ray binary systems with non-thermal radio jets.In some of these systems the jet is expected to be strongly misaligned with the perpendicular to the orbital plane.If the donor star is an early-type star,the jet could collide with the stellar wind producing a standing shock between the compact object and the stellar surface.Relativistic particles injected by the jet can be re-accelerated and isotropized at the colliding region.If the jet has hadronic content,TeV protons will diffuse into the inner,dense wind leading to gamma-ray and neutrino production from interactions with the matter of the wind.In the case of very powerful jets,the wind pressure can be overbalanced and the jet might impact directly onto the stellar surface.We present estimates of the gamma-ray and neutrino luminosities for different sets of parameters in these scenarios and we briefly discuss the effects of this radiation on the donor star and its detectability with current instruments.Key words.X-ray:binaries –stars –gamma-rays:theory –gamma-rays:observations –neutrinos1.IntroductionMicroquasars (MQs)are accreting X-ray binary systems that have shown persistent or episodic non-thermal jet-like ejections (Mirabel &Rodr´ıguez 1999).It is believed that a significant fraction of all accreting black hole (BH)and neutron star (NS)X-ray binaries are likely to exhibit MQ behavior at some epoch during their lifetime.Although it is not observationally required,the jet axis and the or-bital plane of a given MQ system are usually assumed to be approximately perpendicular.However,Maccarone (2002)has shown that the timescale for the BH spin to align with the orbital angular momentum in binary sys-tems is often longer than the lifetime of the system it-self.Additionally,tidal effects upon the disk can induce a precession which could result in a severe misalignment (rwood 1998,Kaufman et al.2002).Precession and strong inclination of the jet can also be the result of the radiative warping of the inner accretion disk (e.g.Wijers &Pringle 1999,Ogilvie &Dubus 2001)or might be due to spin-spin interactions (e.g.Bardeen &Petterson 1975,Sarazin et al.1980).Observationally,there exists sugges-tive evidence for jet misalignments with the normal to the orbital plane in wind-fed accreting BHs.For instance,the jet axis lies at no more than ∼35degrees from the orbital2G.E.Romero&M.Orellana:High-energy emission from microquasars high-energy neutrinos goes through the star.In what fol-lows we characterize the general physical situation and es-timate the gamma-ray and neutrino output of these sys-tems,under a variety of conditions.The results will beof interest for current ground-based TeV gamma-ray tele-scopes and future satellites for MeV-GeV gamma-ray as-tronomy,as well as for km-scale neutrino detectors.2.Jet-wind interactionIn order to make specific calculations we will consider a misaligned MQ with a high-mass companion.The jet axis is assumed,for simplicity,to be parallel to the orbital radius a,and pointing toward the massive star of radius R⋆.As in Romero et al.(2003),we consider an expanding conical jet,i.e.the radius of the cross-section is R j(d)= dθ/2,whereθis the opening angle of the jet(in radians),d is the distance from the compact object,and r is the radial coordinate with origin at the center of the star(d=a−r). Assuming adiabatic expansion,the magneticfield inside the conical jet changes with d asB j(d)=B j(d0) d04πm p r2v(r).(4)The pressure exerted by the stellar wind at a distance r from the star is then:P wind=˙M⋆v(r)B2φ+B2r.The magneticfield of the star can be represented by the standard magnetic ro-tor model(Weber and Davis1967;White1985;Lamers and Cassinelli1999):Bφ/B r=(v⋆/v∞)(1+r/R⋆)and B r=B⋆(R⋆/r)2,where v⋆∼=(0.1−0.2)v∞is the rota-tional velocity at the surface of the star(Conti&Ebbets 1977),and B⋆is the corresponding stellar magneticfield.If the jet propagates with an opening angleθ,at a distance d from the compact object the ram pressure of the jet plasma isP j=L jG.E.Romero &M.Orellana:High-energy emission from microquasars 3Donati et al.(2002).In order to study systems where the jet is balanced by the wind,we will assume different val-ues for the stellar magnetic field and the jet power.After discussing these systems we will turn to MQs with very strong jets in Section 6.Table 1.Basic parameters assumed for the modelMass of the compact object M co 10M ⊙Mass of the donor star M ⋆46.2M ⊙Jet’s injection point d 050R 1g Opening angle of the jet θ5◦Bulk Lorentz factorγbulk 10Radius of the companion star R ⋆15R ⊙Stellar effective temperature T eff40000KMass loss rate˙M ⋆10−5M ⊙yr −1Terminal wind velocityv ∞2500km s −1Compact object accretion rate ˙M disk 10−8M ⊙yr −1Wind velocity index β1Efficiency of the shock χ0.1Orbital radiusa3R ⋆dt|acc =ξZecB,with ξ≃0.015(u/c )2,(8)where u is the shock velocity and all values are in cgs units.The highest energy gained by the particles in the pro-cess is imposed by the different energy losses (synchrotron emission,pp interactions and photopion production)or by the available space in the acceleration region.For the pa-rameters considered in this paper the dominant energy loss is due to pp interactions with the stellar wind mat-ter that pervades the acceleration region.For a relativistic proton (E >1.22GeV)this energy loss can be estimated as in Mannheim &Schlickeiser (1994):−dEc 2B j (d o)GeV ].(10)We shall adopt u/c =0.1for the sub-relativistic shockand u/c =0.5for a relativistic case.For the former E maxp is determined by the losses,whereas in the second case it is fixed by the size constrain,i.e.the maximum gyroradius for a proton is ∼(a −R ⋆).The resulting proton spectrum from the diffusive ac-celeration will be a power-law extending from a minimumenergy (E min p ∼10GeV 1)up to E maxp :N p (E )=K ΓE −Γ,10m p c 2<E <E max p .(11)The index Γis ∼2for a strong non-relativistic shock and ∼1.5for a relativistic shock (e.g.Protheroe 1998).Some fraction χof the energy transported by the jet will be transferred to the particles accelerated at the shock front.We will assume here an efficiency of χ=0.1(Blandford &Ostriker 1978).Then,the constant K Γin (11)can be obtained fromχL j =(a −R ⋆)2cE max p10m p c 2N p (E )E dE.(12)The resulting population of relativistic protons will dif-fuse through the stellar wind,but not all of them willpenetrate up to the densest parts where the probability of pp interactions is higher because of the modulation ef-fect of the wind (Romero &Torres 2003,Torres et al.2004).Whether the particles can reach the base of the wind or not is given by the ratio (ǫ)of the diffusion and convection timescales,which are given by t d =3r 2/D and t c =3r/v (r ),respectively.Here D is the diffusion coeffi-cient defined as (Ginzburg &Syrovatskii 1964):D ∼11From Table 1the Lorentz factor of the jet is ∼10and then those protons at the lower energy tail of the co-moving particle energy distribution (for which the microscopic Lorentz factor is ∼1)are injected at the shock with energies ∼10GeV.4G.E.Romero&M.Orellana:High-energy emission from microquasars Throughǫ=1wefind now the minimum energyE min p (r)below which the particles are taken away by con-vection in the wind(see the explicit expression forǫin the paper by Torres et al.2004).In what follows,we will takeE min p (r s)as the minimum energy of a proton acceleratedat the shock front to collide with a proton of the inner wind.4.Gamma-ray productionWe can now proceed to calculate theπ0gamma-ray lumi-nosity from the inner wind.The differentialγ-ray emissiv-ity fromπ0-decays can be approximated byqγ(Eγ)=4πσpp(E p)2Z(Γ)p→π0G.E.Romero&M.Orellana:High-energy emission from microquasars5 Table2.Some results about the high-energy photon emission in misaligned MQs.The A,B,C letters naming the model indicate a high,middle or low jet-disk coupling,respectively.A110−25001021.792.219030002.210324.11032A210−250010021.792.21900300007.510323.91032B110−311034.20.219030001.910325.41031B210−3110034.20.21900300002.110324.31031B310−31001034.221.319030006.410314.71031B410−310010034.221.31900300001.110324.11031C110−411041.10.219030001.910315.41030C210−4110041.10.21900300002.110314.31030C310−41001041.120.819030006.510304.71030C410−410010041.120.81900300001.110314.110306G.E.Romero &M.Orellana:High-energy emission frommicroquasarsFig.2.Stellar photosphere’s opacity due to photo-pair creation,as function of the γ-ray energy and the distance from the star,for a photon moving radially from the massive star.Upper-right:Optical depth for fixed values of energy.Lower panel:Optical depth for fixed distances.where P ν→µ(E ν)≈1.3×10−6(E ν/TeV)0.8denotes the probability that a νof energy E ν∼1−103TeV,on a tra-jectory through the detector,produces a muon (Gaisser et al.1995).T obs is the observing time and A effthe effective area of the detector.On the other hand,the noise will be given byN = T obsdE νA effF B (E ν)P ν→µ(E ν)∆Ω 1/2,(26)where ∆Ωis the solid angle of the search bin (∆Ω1◦×1◦≈3×10−4sr for an instrument like ICECUBE,Karle 2002)andF B (E ν)≤0.2(E ν/GeV)−3.21GeV −1cm −2s −1sr −1(27)is the νµ+¯νµatmospheric ν-flux (Volkova 1980,Lipari 1993).Using as the integration limits the minimum and maximum energies detectable by the instrument (i.e.1-105TeV)we obtain T obs for a signal-to-noise ratio S/N =3.The results are in all the cases (models A1to C4)greater than several thousands years,rendering the detection im-practical with the current sensitivity.Once again,these are lower limits,since the duty cycle is not 1.Only in the case of very powerful jets with q j >0.1a detection might be possible on human-life timescales.We will discuss this case in the next section.Table 3.Some results about the neutrino emission in mis-aligned MQs.Case D 1corresponds to the direct impact of a jet with q j =0.1onto the stellar surface.A 14.010321.71032A 23.310325.41031B 13.710311.61031B 23.110315.41030B 33.910311.71031B 43.310315.41030C 13.710301.61030C 23.110305.41029C 33.910301.71030C 43.310305.51029G.E.Romero&M.Orellana:High-energy emission from microquasars76.Powerful jets and direct interaction with thestarWe consider now a heavy jet directly impacting the star(q j=0.12).The proton spectrum of the relativistic jetflowis assumed to be a power law N′p(E′p)=KΓE′−Γp,valid forE′p min≤E′p≤E′p max,in the co-moving jet frame.The cor-responding particleflux will be J′p(E′p)=(c/4π)N′p(E′p).Since the jet expands(in a conical way),the protonfluxcan be written as:J′p(E′p)=cdnE′p−Γ,(28)where n is positive and we assume n=2(which corre-sponds to the conservation of the number of particles,see Ghisellini et al.1985),and a prime refers to the jet frame. Using relativistic invariants,it can be proved that the pro-tonflux reaching the surface of the star,in the lab frame, becomes(e.g.Romero et al.2003)J p(E p)=cKΓa−R⋆n×γ−Γbulk E p+βb1+βb E p E2p−m2p c4 ,(29)whereγbulk is the jet Lorentz factor,βb is the correspond-ing velocity in units of c,and we have considered protons with small transverse momentum(hence the lack of de-pendency in the particle angle when compared with the corresponding expression in Romero et al.2003).The number density n0′of particlesflowing in the jet at R0=R(d0)can be determined as in Romero et al. (2003)and the normalization constant KΓcan be derivedprovided that E′maxp >>E′minp.Since E′minp∼1GeV,thisis always the case,andKΓ=n0′(Γ−1)(E′minp)Γ−1.(30)In the numerical calculations we have considered E′maxp =100TeV,γbulk=10,and two cases for the proton energydistribution in the jet3:Γ=2andΓ=1.5.The gamma-rays generated by the jet-star interaction will be absorbed by the electromagnetic cascades in thestar.The main signature of such cascades could be a rather broad e+−e−annihilation line.The neutrinoflux from charged pion decays will be significantly larger than in thecase of the jet-wind interactions.For the density profile of the star we have usedρ(r)=ρc 1−(r/R⋆)2 ,(31)8G.E.Romero&M.Orellana:High-energy emission from microquasarstems the jet could be periodically directed towards the companion star(Butt et al.2003).This means that2-4 of the variable EGRET sources at low galactic latitudes might be associated with misaligned MQs.Hints of peri-odic variability could help to identify these sources.Their main footprints,however,would be a stronger TeV emis-sion than what is expected in normal MQs.Hence,fu-ture observations with Cherenkov telescopes like HESS, MAGIC or Veritas might lead to the identification of these sources.8.ConclusionsThe jets of MQs can form a small angle respect to the or-bital plane.In some high-mass X-ray binary systems the jet could be directed straight to the companion star.We have shown that in such a situation the wind of the star can balance the jet pressure in many cases.A jet-wind collision region is formed between the star and the com-pact object,with a contact discontinuity separating both shocked media.Relativistic particles injected by the jet in the strong shock can be re-accelerated up to very high energies and isotropized in this region.These particles dif-fuse into the inner wind as far as diffusion dominates over convection.Gamma-rays and neutrinos can be then pro-duced in the densest part of the wind.We have presented calculations of the gamma-ray luminosity,which might be detectable through high-energy telescopes.The neu-trinoflux is usually below the sensitivity of km-scale de-tectors like ICECUBE unless extremely powerful jets are assumed.Such jets could reach the star,triggering cas-cades and producing nucleosynthesis there,as discussed by Butt et al.(2003).We have also shown that photon-photon absorption of gamma-rays with energies below10 TeV can initiate electromagnetic cascades in the stellar photosphere,leading to MeV-GeV sources that might con-tribute to the population of variable gamma-ray sources detected by EGRET at low galactic latitudes.Future in-struments like GLAST will help to unveil the nature of these sources.Acknowledgements.We thank J.M.Paredes and V.Bosch-Ramon for valuable discussions and comments on the manuscript.We also thank an anonymous referee who made important suggestions that led to a significant improvement of the manuscript.This research has been supported by 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脑状态指数和Narcotrend指数用于预测全麻苏醒期意识恢复的比较
脑状态指数和Narcotrend指数用于预测全麻苏醒期意识恢复的比较目的探讨患者全麻苏醒期的意识恢复采用脑状态指数和Narcotrend指数预测的临床比较情况。
方法选取我院行腹腔镜下胆囊切除术的患者30例，术中给予靶控输注丙泊酚（TCI）、瑞芬太尼保持患者麻醉状态，观察并记录患者全麻苏醒期意识恢复时脑状态指数和Narcotrend指数水平变化。
结果CSI、NTI、丙泊酚Ce在苏醒期不同意识水平变化差异具有统计学意义（P＜0.05或P＜0.01）；CSI、NTI、丙泊酚Ce预测患者全麻苏醒期意识水平恢复的Pk值均不小于0.8，这与Pk值=0.5相比较，结果具有统计学差异（P＜0.05）。
结论脑状态指数和Narcotrend指数均能及时的反映出患者全麻苏醒期意识恢复不同阶段的水平变化。
Abstract：Objective To explore the clinical comparison of brain state index and Narcotrend index in the recovery of consciousness of patients with general anesthesia.Methods 30 cases of patients with laparoscopic cholecystectomy were selected，patients were given target controlled infusion of propofol（TCI），and the patients were kept in a state of anesthesia.Results There were significant differences in the levels of Ce，NTI，and propofol Pk（P＜0.05 or P＜0.01）；CSI，NTI，and propofol Ce were not less than 0.8 of=0.5 in the patients with general anesthesia.Conclusion The brain state index and Narcotrend index can reflect the level of different stages of the recovery of consciousness in patients with general anesthesia.Key words：Cerebral state index；Narcotrend index；Recovery period of general anesthesia；Consciousness recovery目前，临床上采用脑电信号监测患者全麻的麻醉深度。
迈克尔逊干涉仪测量光波的波长实验报告
迈克尔逊干涉仪测量光波的波长实验报告英文回答：The Michelson Interferometer is a highly sensitive and precise measuring instrument invented by Albert A. Michelson in the late 19th century. It utilizes the principle of interference to accurately determine the wavelength of light. The interferometer is an invaluable tool for physicists as it aids in unraveling the mysteries of the universe's fundamental structure and the nature of light itself.Principle of Operation:The Michelson Interferometer consists of two perpendicular arms, each containing a mirror. Light from a coherent source is split into two beams using a beam splitter, with each beam traveling down one arm of the interferometer. The beams are then reflected back by the mirrors and recombined at the beam splitter, where theyinterfere with each other. Depending on the path length difference between the two arms, the interference can be either constructive or destructive.Measurement of Wavelength:To measure the wavelength of light, one arm of the interferometer is adjusted, causing a shift in the interference pattern. By carefully measuring the distance moved by the mirror, one can calculate the path length difference between the two arms. The wavelength of the light is then determined using the following formula:```。
迈克尔逊干涉仪测量光波的波长实验报告
迈克尔逊干涉仪测量光波的波长实验报告英文回答：Michaelson Interferometer Experiment to Measure the Wavelength of Light Waves。
Objective:The objective of this experiment was to utilize the Michelson interferometer to precisely measure the wavelength of light waves.Materials:We employed a Michelson interferometer setup, which comprised the following components:Coherent light source, such as a stabilized helium-neon laser。
Beam splitter。
Two mirrors。
Photodetector。
Data acquisition system。
Procedure:1. Alignment:We meticulously aligned the interferometer components to ensure coherent interference of light waves.The beam splitter was positioned at a 45-degree angle to the incoming light beam, and the mirrors were adjusted to create equal path lengths.2. Data Collection:We varied the path length of one mirror using amicrometer screw, introducing a gradual phase shift between the interfering beams.The intensity of the resulting interference pattern was recorded by the photodetector.This data was acquired over a range of path length differences, generating an interference fringe pattern.3. Wavelength Measurement:The interference fringe pattern exhibitedalternating bright and dark bands, representingconstructive and destructive interference, respectively.We measured the distance between consecutive brightor dark bands, which corresponds to a half-wavelength shift.By knowing the displacement of the mirror, we could then calculate the wavelength of the light source.Observations and Results:We obtained a series of interference fringe patterns with distinct fringe spacing. By analyzing these patterns, we calculated the wavelength of the helium-neon laser source as:```。
测定mgf2薄膜的复折射率光谱的英文
测定mgf2薄膜的复折射率光谱的英文The Characterization of the Refractive Index Spectrum of MgF2 Thin FilmsThe optical properties of thin-film materials have become increasingly important in various technological applications, ranging from optoelectronic devices to optical coatings. Among the numerous thin-film materials, magnesium fluoride (MgF2) has gained significant attention due to its unique optical characteristics, such as a wide transparent spectral range, low refractive index, and excellent chemical stability. Accurate determination of the refractive index spectrum of MgF2 thin films is crucial for the design and optimization of optical components and systems.In this study, we aim to present a comprehensive characterization of the refractive index spectrum of MgF2 thin films. The refractive index of a material is a fundamental optical property that describes the speed of light propagation within the material. The refractive index can be wavelength-dependent, leading to a refractive index spectrum, which is essential for understanding the optical behavior of thin-film materials.To achieve this goal, we employed a combination of experimental techniques and theoretical analysis. The MgF2 thin films were deposited on glass substrates using a well-established deposition method, such as thermal evaporation or sputtering. The thickness of the films was carefully controlled to ensure the accuracy of the refractive index measurements.The refractive index spectrum of the MgF2 thin films was determined using a spectroscopic ellipsometry technique. Ellipsometry is a non-destructive optical characterization method that measures the change in the polarization state of light upon reflection from the sample surface. By analyzing the ellipsometric data, the refractive index and other optical properties of the thin films can be accurately determined.The measurement process involved placing the MgF2 thin-film sample in the ellipsometer and collecting the ellipsometric data over a wide range of wavelengths, typically from the ultraviolet to the near-infrared region of the electromagnetic spectrum. The collected data were then analyzed using appropriate optical models and numerical algorithms to extract the refractive index spectrum of the MgF2 thin films.To ensure the reliability and accuracy of the refractive index data, several factors were considered during the measurement andanalysis processes. These factors include the surface roughness of the thin films, the potential presence of anisotropy, and the influence of the underlying substrate. Appropriate mathematical models were employed to account for these factors and obtain a accurate refractive index spectrum.The results of the study revealed the detailed refractive index spectrum of the MgF2 thin films over the measured wavelength range. The refractive index was found to exhibit a strong wavelength dependence, with the value decreasing as the wavelength increased. This behavior is consistent with the dispersion characteristics ofMgF2, which is known to have a low refractive index and high transparency in the visible and near-infrared regions.Furthermore, the study also investigated the potential effects of film thickness and deposition conditions on the refractive index spectrum. By varying these parameters, the researchers were able to understand the relationship between the thin-film properties and the resulting optical characteristics. This knowledge can be valuable for tailoring the optical performance of MgF2 thin films for specific applications.The findings of this study contribute to the existing understanding of the optical properties of MgF2 thin films and provide a reliable reference for the refractive index spectrum. This information is crucialfor the design and optimization of various optical components and devices that utilize MgF2 as a key material, such as antireflective coatings, optical filters, and optical waveguides.In conclusion, this comprehensive study on the refractive index spectrum of MgF2 thin films offers valuable insights for researchers and engineers working in the field of optical thin-film technology. The accurate characterization of the refractive index spectrum presented here can facilitate the development of advanced optical systems and devices that harness the unique optical properties of MgF2.。
迈克尔逊干涉仪的使用实验报告
迈克尔逊干涉仪的使用实验报告英文回答：Introduction。
The Michelson interferometer is a scientific instrument that uses interference to measure the relative displacement of two objects with great precision. It was invented by Albert Michelson in 1881 and has been used in a widevariety of applications, including:Measuring the speed of light。
Determining the wavelength of light。
Testing the theory of relativity。
Measuring the size of molecules。
Detecting gravitational waves。
Experimental Procedure。
In this experiment, we used a Michelson interferometer to measure the wavelength of a laser. The interferometer was set up on an optical table, and a laser was shone through it. The laser beam was split into two beams by a beam splitter, and the two beams were then reflected back toward the beam splitter by two mirrors. The two beams recombined at the beam splitter, and the resulting interference pattern was observed on a screen.The wavelength of the laser was calculated by measuring the distance between the bright fringes in the interference pattern. The distance between the fringes is equal to:```。
迈克尔逊干涉仪实验报告
迈克尔逊干涉仪实验报告英文回答：Michaelson interferometer is an important optical instrument that is used to measure the speed of light and the index of refraction of materials. It was invented by Albert A. Michelson in 1881. The interferometer consists of two arms of equal length that are perpendicular to each other. A beam of light is split into two beams, and each beam is sent down one of the arms. The beams are then reflected back to the point where they were split, and they interfere with each other. The interference pattern can be used to measure the speed of light and the index of refraction of the materials in the arms.The Michelson interferometer has been used to make many important discoveries about the nature of light. For example, it was used to measure the speed of light towithin 1/100th of a percent. It was also used to show that the speed of light is the same in all directions,regardless of the motion of the observer. This result wasin conflict with the prevailing theory of light at the time, which predicted that the speed of light would be different depending on the direction of motion.The Michelson interferometer is still used today in a variety of applications, including measuring the index of refraction of materials, testing optical components, and studying the properties of light. It is a versatile and powerful instrument that has played an important role inthe development of optics.中文回答：迈克尔逊干涉仪是一种重要的光学仪器，用于测量光速和材料的折射率。
迈克尔逊干涉仪实验报告
迈克尔逊干涉仪实验报告英文回答：The Michelson interferometer is a device used to measure the speed of light and to test the theory of special relativity. It was invented by Albert Michelson in 1881. The interferometer consists of two mirrors that are placed at a distance of several meters from each other. A beam of light is split into two beams, and each beam is reflected by one of the mirrors. The two beams are then recombined, and the interference pattern is observed.The speed of light can be measured by measuring the distance between the mirrors and the time it takes for the light to travel from one mirror to the other and back. The theory of special relativity can be tested by measuring the speed of light in different directions. If the theory of special relativity is correct, then the speed of light will be the same in all directions.The Michelson interferometer has been used to make many important measurements. In 1887, Michelson and Edward Morley used the interferometer to measure the speed of light. They found that the speed of light was the same in all directions, which was a confirmation of the theory of special relativity.In 1905, Albert Einstein published his theory of special relativity. Einstein's theory explained the results of the Michelson-Morley experiment. Einstein's theory showed that the speed of light is the same in all inertial frames of reference. This means that the speed of light is the same for all observers, regardless of their motion.The Michelson interferometer is a very sensitive instrument. It can be used to measure very small changes in the speed of light. The interferometer has been used to study the effects of gravity on the speed of light.The Michelson interferometer is a valuable tool for physicists. It has been used to make many important measurements, and it has helped us to understand theuniverse better.中文回答：迈克尔逊干涉仪是一种用来测量光速和检验狭义相对论的装置。
sat阅读教程文件
Virtually everything astronomers known about objectsoutside the solar system is based on the detection ofphotons-quanta of electromagnetic radiation. Yet thereis another form of radiation that permeates the universe: (5) neutrinos. With (as its name implies) no electric charge,and negligible mass, the neutrino interacts with otherparticles so rarely that a neutrino can cross the entireuniverse, even traversing substantial aggregations ofmatter, without being absorbed or even deflected. Neu-(10)trinos can thus escape from regions of space where lightand other kinds of electromagnetic radiationare blockedby matter. Furthermore, neutrinos carry with theminformation about the site and circumstances of theirproduction: therefore, the detection of cosmic neutrinos (15)could provide new information about a wide variety ofcosmic phenomena and about the history of the uni-verse.But how can scientists detect a particle that interact sso infrequently with other matter? Twenty-five years(20)passed between Pauli’s hypothesis that the neutrinoexisted and its actual detection: since then virtually allresearch with neutrinos has been with neutrinos created artificially in large particle accelerators and studiedunder neutrino microscopes. But a neutrino telescope,(25) capable of detecting cosmic neutrinos, is difficult to co- nstruct. No apparatus can detect neutrinos unless it isextremely massive, because great mass is synonymouswith huge numbers of nucleons (neutrons and protons),and the more massive the detector, the greater the pro-(30) bability of one of its nucleon’s reacting with a neutrino. In addition, the apparatus must be sufficiently shieldedfrom the interfering effects of other particles.Fortunately, a group of astrophysicists has proposeda means of detecting cosmic neutrinos by harnessing the(35) mass of the ocean. Named DUMAND, for Deep Under-water Muon and Neutrino Detector, the project calls forplacing an array of light sensors at a depth of five kilo-meters under the ocean surface. The detecting medium isthe seawater itself: when a neutrino interacts with a(40)particle in an atom of seawater. the result is a cascade of electrically charged particles and a flash of light that can be detected by the sensors. The five kilometers of sea-water above the sensors will shield them from the interf-ering effects of other high-energy particles raining down(45) through the atmosphere.The strongest motivation for the DUMAND projectis that it will exploit an important source of informationabout the universe. The extension of astronomy fromvisible light to radio waves to x-rays and gamma rays(50) never failed to lead to the discovery of unusualobjectssuch as radio galaxies, quasars, and pulsars. Each ofthese discoveries came as a surprise. Neutrino astronomywill doubtless bring its own share of surprises.1. Which of the following titles best summarizes the passage as a whole?(A) At the Threshold of Neutrino Astronomy(B) Neutrinos and the History of the Universe(C) The Creation and Study of Neutrinos(D) The DUMAND System and How It Works(E) The Properties of the Neutrino2. With which of the following statements regarding neutrino astronomy wouldthe author be most likely to agree?(A) Neutrino astronomy will supersede all present forms of astronomy.(B) Neutrino astronomy will be abandoned if the DUMAND project fails.(C) Neutrino astronomy can be expected to lead to major breakthroughs inastronomy.(D) Neutrino astronomy will disclose phenomena t hat will be more surprising than past discoveries.(E) Neutrino astronomy will always be characterized by a large time lag between hypothesis and experimental confirmation.3. In the last paragraph, the author describes the development of astronomy in order to(A) suggest that the potential findings of neutrino astronomy can be seen aspart of a series of astronomical successes(B) illustrate the role of surprise in scientific discovery(C) demonstrate the effectiveness of the DUMAND apparatus in detecting neutrinos(D) name some cosmic phenomena that neutrino astronomy will illuminate(E) contrast the motivation of earlier astronomers with that of theastrophysicists working on the DUMAND project4.According to the passage, one advantage that neutrinos have for studies inastronomy is that they(A) have been detected for the last twenty-five years(B) possess a variable electric charge(C) are usually extremely massive(D) carry information about their history with them(E) are very similar to other electromagnetic particles5. According to the passage, the primary use of the apparatus mentioned in lines 24-32 would be to(A) increase the mass of a neutrino(B) interpret the information neutrinos carry with them(C) study the internal structure of a neutrino(D) see neutrinos in distant regions of space(E) detect the presence of cosmic neutrinos6. The passage states that interactions between neutrinos and other matter are(A) rare(B) artificial(C) undetectable(D) unpredictable(E) hazardous7. The passage mentions which of the following as a reason that neutrinos arehard to detect?(A) Their pervasiveness in the universe(B) Their ability to escape from different regions of space(C) Their inability to penetrate dense matter(D) The similarity of their structure to that of nucleons(E) The infrequency of their interaction with other matter8. According to the passage, the interaction of a neutrino with other mattercan produce(A) particles that are neutral and massive(B) a form of radiation that permeates the universe(C) inaccurate information about the site andcircumstances of the neutrino’s production(D) charged particles and light(E) a situation in which light and other forms of electromagnetic radiation are blocked9. According to the passage, one of the methods used to establish the properties of neutrinos was(A) detection of photons(B) observation of the interaction of neutrinos with gamma rays(C) observation of neutrinos that were artificially created(D) measurement of neutrinos that interacted with particles of seawater(E) experiments with electromagnetic radiationCorrect Answers：ACADEAEDC以上就是这一例SAT阅读文章模拟题的全部内容，包括了9道题目。
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a r X i v :a s t r o -p h /0404096v 1 5 A p r 2004The Baikal Neutrino Telescope:Results,Plans,LessonsC.Spiering for the BAIKAL CollaborationDESY Zeuthen,Platanenallee 6,D-15738Zeuthen,Germanychristian.spiering@desy.deThe BAIKAL Collaboration:V .Aynutdinov 1,V .Balkanov 1,I.Belolaptikov 4,L.Bezrukov 1,N.Budnev 2, A.Chensky 2, D.Chernov 3,I.Danilchenko 1,Zh.-A.Dzhilkibaev 1,G.Domogatsky 1,A.Dyachok 2,O.Gaponenko 1,O.Gress 2,T.Gress 2,A.Klabukov 1,A.Klimov 8,S.Klimushin 1,K.Konischev 4, A.Koshechkin 1,V .Kulepov 6,L.Kuzmichev 3,Vy.Kuznetzov 1,B.Lubsandorzhiev 1,S.Mikheyev 1,enin 6,R.Mirgazov 2,N.Moseiko 3,E.Osipova 3,A.Panfilov 1,G.Pan’kov 2,L.Pan’kov 2,Yu.Parfenov 2,A.Pavlov 2,E.Pliskovsky 4,P.Pokhil 1,V .Polecshuk 1,E.Popova 3,V .Prosin 3,M.Rosanov 7,V .Rubtzov 2,Yu.Semeney 2, B.Shaibonov 1, C.Spiering 5, B.Tarashansky 2,R.Vasiliev 4,E.Vyatchin 1,R.Wischnewski 5,I.Yashin 3,V .Zhukov 1(1)Institute for Nuclear Research,Moscow,Russia,(2)Irkutsk State University,Irkutsk,Russia,(3)Skobeltsyn Institute of Nuclear Physics MSU,Moscow,Russia,(4)Joint Institute for Nuclear Research,Dubna,Russia,(5)DESY–Zeuthen,Zeuthen,Germany,(6)Nizhni Novgorod State Technical University,(7)St.Peterburg State Marine University,St.Peterburg,Russia,(8)Kurchatov Institute,Moscow,RussiaAbstractWe review recent results on the search for high energy extrater-restrial neutrinos,neutrinos induced by WIMP annihilation and neutrinos coincident with Gamma Ray Bursts as obtained with the Baikal neutrino telescope NT-200.We describe the mod-erate upgrade of NT-200towards a ∼10Mton scale detector NT-200+.We finally draw a few lessons from our experience which may be of use for other underwater experiments.I.I NTRODUCTIONThe Baikal Neutrino Telescope NT-200is operated in Lake Baikal,Siberia,at a depth of 1.1km.A description of the de-tector as well as physics results from data collected in 1996and 1998(70and 234live days,respectively)have been presented elsewhere [1,2].Here we present new limits including data taken in 1999(268live days).We note that the year 2003marks the tenth anniversary of the deployment of NT-36,the pioneering first stationary under-water array [3,4].Fig.1shows a textbook neutrino event (an upward moving muon track)recorded with the early 4-string configuration of 1996[5].Figure 1:Upward going muon track with 19fired channels,recorded in 1996.Hit channels are marked in color,with the size of the aura indicating the recorded amplitude.II.S EARCH FOR EXTRATERRESTRIALHIGH ENERGY NEUTRINOSThe survey for high energy neutrinos is focused to bright cas-cades produced at the neutrino interaction vertex in a large vol-ume around the neutrino ck of significant light scattering allows to monitor a volume exceeding the geomet-rical volume by an order of magnitude.This results in sen-sitivities of NT-200comparable to those of the much larger Amanda-B10detector.The background to this search are bright bremsstrahlung flashes along muons passing far outside the array (see [6]for details).Candidate events do not show a statistically significant excess of hit multiplicites compared to the simulated back-ground from atmospheric muons.Assuming an E −2shape of the neutrino spectrum and a flavor ratio νe :νµ:ντ=1:1:1,the new,preliminary 90%c.l.upper limit with re-spect to the flux of all three flavors is Φνe +νµ+ντE 2=1.3·10−6cm −2s −1sr −1GeV,about twice below previous results [6].The preliminary limit on ˜νe at the W -resonance energy is:Φ˜νe ≤5.4×10−20cm −2s −1sr −1GeV −1.Fig.2shows the ex-perimental upper limits obtained by BAIKAL (this work),andAMANDA[7],as well as the projected sensitivity for NT-200+(see below).Limits are compared to SSDS[8]and MPR[9] predictions.The slanted lines at the left side represent the at-mospheric neutrinofluxes(dashed forνµ,solid forνe).Figure2:Experimental upper limits on neutrinofluxes(see text for explanation).III.S EARCH FOR NEUTRINOSCOINCIDENT WITH GRB SWe have searched for high energy cascades coincident with 772Gamma Ray Bursts(GRB)recorded between April1998 and February2000by the BATSE detector and falling into on-line periods of NT-200(386triggered GRB,336non-triggered from Stern catalogue).After cuts for background reduction, we are left with one event within one of the±100-second win-dows,where0.47events would have been expected from ac-cidental coincidences.Precise limits on thefluence are being derived at present.With an effective volume in the Megaton range,NT-200is the largest Northern detector for high energy neutrinos from GRBs.IV.S EARCH FOR NEUTRINOS FROMWIMP ANNIHILATIONThe search for WIMPs with the Baikal neutrino telescope is based on a possible signal of nearly vertically upward going muons,exceeding theflux of atmospheric neutrinos(see[10]). Note that the threshold of∼10GeV for this analysis is lower than that of∼15GeV for atmospheric neutrinos spread across the full lower hemisphere.Fig.3(top)demonstrates that the angular distribution of events passing a specialfilter for events close to the vertical is well described by simulations including the effect of neutrino oscillations(assumingδm2=2.5·10−3 eV2).Figure3:Angular distribution of selected neutrino candidates com-pared to expected distributions including(full line)and excluding (dotted line)the effect of oscillations.With no significant excess observed,we derive improved upper limits on theflux of muons from the direction of the cen-ter of Earth related to WIMP annihilation.Fig.3(bottom)com-pares our new limits to those obtained by other experiments (see[10]for references).Figure4:Flux limits from different experiments as a function of WIMP mass.V.U PGRADE TO NT200+NT-200+is an upgrade of NT-200by three sparsely instru-mented distant outer strings(see Fig.5).The fenced volume is a few dozen Mtons.A prototype string of140m length with 12optical modules was deployed in March2003,and electron-ics,data acquisition and calibration systems for NT-200+have been tested.The3strings allow for dramatically better vertex reconstruction of high energy cascades than with NT-200alone (see Fig.6).This,in turn,allows a much better determinationof the energy and makes NT-200+a true discovery detector with respect to reactions within the mentioned fiducial volume.(This is in contrast to NT-200which is an excellent exclusion experiment but would have certain difficulties to prove –for a single event outside its geometrical volume –that the signal is indeed due to a far high-energy event and not to a closer medium-energy event.)NT-200+will be installed in 2004and2005.Figure 5:Configuration of NT-200+.R r e c0, m, mFigure 6:Reconstructed vs.simulated coordinates of cascades in NT-200+(black rectangles)and NT-200(crosses).VI.A G IGA -TON D ETECTOR ?First discussions have started on an even larger detector of the order of a cubic kilometer in Lake Baikal.The configu-ration of such a detector will be consequently tailored to cer-tain classes of events and should complement Mediterranean arrays.A possible design was sketched in [2].Given the draw-backs of stronger absorbtion and shallower depth compared to Mediterranean sites,this idea rests on the proven,stable de-ployment procedures,lower-cost considerations and possible national funding strategies.However,even in the case of strongnational funding,such a project would need international par-ticipation.VII.S OME LESSONSWe finally summarize some lessons which may be of use for all underwater arrays.A.LeakageThe early history of Baikal could have been written as a his-tory of leaking feed-throughs,connectors and pressure hous-ings.After having designed a special connector tailored to depths up to ∼1.6km (the maximum depth in Lake Baikal),this phase was overcome.NT-36did not suffer from leaks.In the mean time,more than 1000connectors and feed-throughs are in operation at 1.1km depth,and the failure rate is less than 1per year.Clearly,detectors much deeper,like the Mediter-ranean ones,have to make use of different technologies.Still,is seems now obvious that instruments with hundreds of pres-sure spheres and more than thousand connectors can work in deep water over many years,with tolerable leakage rates –a statement which ten years ago would have been questioned by many oceanographers.B.SedimentationSedimentation and bio-fouling are a concern in Lake Baikal.The performance of the up-down symmetric NT-36detector,with the same number of optical modules facing upward and downward,was particularly affected by sedimentation [3].The sensitivity of the upward looking modules with respect to at-mospheric muons decreased to 35%after one year [11].At present,only two of the 12layers of NT-200have upward fac-ing modules.The glass spheres are dressed with a tapering hat of plastic foil.Much of the sediments glide along the foil and do not stick to the hat.The effect of sedimentation,i.e.a pro-gressively decreasing sensitivity of the upward looking mod-ules,is weakened,and an acceptable functionality may be kept by cleaning the hats once every two years.This is important since the outer strings of NT-200+will be up-down symmetric.We conclude that symmetric configurations can be operated in Lake Baikal,but only if the optical moudules can be easily hauled up,inspected and cleaned.The same limitation should hold for those Mediterannean sites with strong biological ac-tivity.C.Reliability and repairThe possibility to haul up the array and to repair connectors was a key for NT-200’s operation.In the very beginning,about 40%of the optical modules turned non-operational after one year of operation due to failures in electronics.Clearly this was not tolerable,be it with or without the possiblity to repair failed components.In the mean time the failure rate reduced toless than5%per year.This lower rate,combined with the pos-sibility to repair failed components results in a tolerable regime of operation and maintenance.From our experience we would recommend designs which give a not too complicated access to deployed parts of the detector.D.Electro-corrosionWith the reliability of the detector itself improving from year to year,we were faced by another,non-expected problem:we observed electro-corrosion along the cables to shore.Actually electro-corrosion was thought to be negligible since the fresh water of Lake Baikal is nearly free of minerals and salts and is a bad conductor of electricity.Much of the return current was thought toflow along the outer metal jacket of the shore cable (white arrows infigure7)and not through the water.Figure7:Electro-corrosion along shore cables.See text for explana-tions.During the last year it became clear that the cable arming showed damages at the points indicated in thefigure.The rea-son seems to be that close to the shore the current leaks into ground and propagates there with a low resistance compared to the cable,and that also currentflows trough the water at the depth of the big metallic,umbrella-like support frame of NT-200(black arrows).At these points,strong electro-corrosion is observed.It led to the loss of two of the four shore cables in the last year.The cables will be replaced by new cables in 2004,and the distance between the vertical part of the shore cable and NT-200will be increased.Electro-corrosion should be an even stronger issue for salt water detectors,as shown by the DUMAND history.The Baikal experience can certainly not be translated to different designs of power distribution and return current.Still it may suggest that one should be prepared to unpleasant surprises and necessary design changes.E.Staged approachA staged approach seems mandatory when building a large instrument in a new and challenging environment like deep water.The idea that one can already in the design phase ac-count for all possible problems has been disqualified not only by the Baikal experience but also by DUMAND,NESTOR and ANTARES.The operation of prototype detectors and the readi-ness for technological modifications is of key importance.F.Looking beyond the geometrical volume Underwater detectors do not suffer from strong light scattering as does ice.Therefore the timing information from distant light sources is not strongly dispersed.This opens the possibility to monitor a huge volume around the detector.A few strings far outside,like those planned for NT-200+,can dramatically im-prove the sensitivity to PeV processes.Due to best background rejection,the most efficient region is that below the geometri-cal volume of the detector.Apart from stronger bottom water currents and slighlty worse water quality close to ground,this may be another argument not to place the detector as deep as possible,but a few hundred meters above ground.This work was supported by the Russian Ministry of Re-search,the German Ministry of Education and Research and the Russian Fund of Basic Research(grants03-02-31004, 02-02-17031,02-07-90293and01-02-17227),Grant of Pres-ident of Russia NSh-1828.2003.2and by the Russian Federal Program“Integration”(project no.E0248).R EFERENCES[1]Zh.-A.Dzhilkibaev for the BAIKAL collaboration,Proc.Int.Workshop on Neutrino Telescopes(Venice2001);and astro-ph/0105269.[2]G.V.Domogatsky for the Baikal collaboration,Proc.XXth Int.Conf.on Neutrino Physics and Astrophysics (Munich2002)353;and astro-ph/0211571.[3]I.Belolaptikov et al.,Astropart.Phys.7(1997)263.[4]Underwater:The tide turns,CERN Courier33/9(1993)36.[5]I.Belolaptikov et al.,Astropart.Phys.12(1999)75.[6]V.A.Balkanov et al.,Astropart.Phys.14(2000)61.[7]see the talk of E.Bernardini in these proceedings.[8]F.W.Stecker et al.,Phys.Rev.Lett.66(1991)2697.[9]K.Mannheim,R.Protheroe,J.Rachen,Phys.Rev.D63(2001)023003.[10]V.Balkanov et al.,Phys.Atom.Nucl.66(2003)503.[11]R.I.Bagduev et al.,Nucl.Inst.Meth.A420(1999)138.。