s=4.03GeV下τ±→π+π－π±υτ衰变的测量

利用北京谱仪(BES)在4.03GeV正负电子对撞能量下获取的数据,[研究了,τ+τ-产生过程.借助双标记方法分析了τ±→π+π-π±υτ衰变事例.测定分支比Br(τ±→a1±υτ→ρ0π±υτ,ρ0→π+π-=(7.3±0.5)%,Br(τ±→K*±υτ→Ks0π±υτ,Ks0→π+π-)=(0.6±1.5)×10-3.并由Daliz投影分布的分析,确认a1的主要衰变方式ρπ.同时,也观察到a1衰变中以S波贡献为主的现象.采用Kuhn模型拟合实验数据,得到:ma1=1.24±0.02GeV,Γa1T=0.57±0.07GeV.     

Multi-quasiparticle excitations in ~(145)Tb

Nuclei with N and Z near magic number can be well described by the nuclear shell model. The 145Tb nucleus has a valence proton and a pair of neutron holes with respect to the doubly closed 146Gd nucleus. Therefore, it is expected that the excitations in 145Tb be dominated by single-particle configurations. A detailed measurement of the excitation scheme in 145Tb would give us an opportunity to examine the behavior of multi-particle excitations involving high angular momentum orbits and provi…     

Neutral fermion excitations in the Moore-Read state at filling factor ν = 5/2

We present evidence supporting the weakly paired Moore-Read phase in the half-filled second Landau level, focusing on some of the qualitative features of its excitations. Based on numerical studies, we show that systems with odd particle number at the flux N(?)=2N-3 can be interpreted as a neutral fermion mode of one unpaired fermion, which is gapped. The mode is found to have two distinct minima, providing a signature that could be observed by photoluminescence. In the presence of two quasiparticles the same neutral fermion excitation is shown to be gapless, confirming expectations for non-abelian statistics of the Ising model with degenerate fusion channels 1 and ψ.     

i=0替代i≠0的误差分析

用透射光栅测定光波波长,一般在分光计上进行,常用的方法是使i=0,这时光栅方程 dsinθ=kλ k=±1,±2,… (1) 当入射光束与光栅面法线成i角时,根据相邻光束的光程差计算,光栅方程为 d(sini±sinθ)=kλ (2) k=±l,±2,…式中“+”号表示入射光束与衍射光束在法线的同侧,而“-”号表示入射光束和衍射光束在法线的异侧。通常实验是在调节好分光计后,把透射光栅置于平台上,使汞灯光源通过平行光管垂直照射到光栅上,转动望远镜到一侧衍射     

Study of D±s→μ±vμ at Belle

We present a preliminary measurement of the B(Ds→μvμ) with the Belle experiment at the KEKB collider. We select Ds→μvμ decays with a method that provides a high-purity of the selected sample and an absolute measurement of the branching fraction. The results are based on a data sample of 550 fb-1 and are compared to similar measurements by other experiments as well as to the predictions of LQCD. We conclude with short prospects for improvements in the accuracy of the measurement.     

T=±∞状态的特性

负绝对温度出现以来,有不少人对它进行了研究．例如,Ｒａｍｓｅｙ［１］最先对负温度１）情况下的热力学及统计物理学作了扼要的阐述,并指出负温度比正的更高．随后Ｈｅｃｈｔ［２］,Ｖｙｓｉｎ［３］及其他一些人［４］又对负温度下的平衡和稳定的条件以及有关的一些问题进行了研究．从这些研究的结果得出一个重要的结论：无论是Ｔ＞０,还是Ｔ＜０,都有Ｃｘ＞０,（１）这里Ｃｘ表示系统外参量Ｘ保持不变时的热容量．近?...     

Yrast excitations in A = 126–131 Te nuclei from deep inelastic 130Te+64Ni reactions

Thick target γγ coincidence measurements for the system ¹³⁰Te + 275 MeV ⁶⁴Ni have been performed using the GASP Ge detector array at Legnaro. For the isotopic assignments of previously unknown γ-ray cascades, prompt γγ coincidences observed between Te and Ni partner products were of vital importance. The results yield much new information about excited states of moderate spins in A = 126–131 tellurium nuclei, especially about yrast excitations of the little studied odd-A isotopes ¹²⁷Te, ¹²⁹Te, and ¹³¹Te. Level systematics of tellurium nuclei are presented, and both single-particle and collective aspects of the level spectra are discussed.     

Variation of Xe concentration in a high pressure Ar/Xe laser with coaxial e-beam pumping

A series of measurements on the high pressure (up to 18 bar) coaxial e-beam pumped Ar/Xe laser has been made at high power loading (up to 25 MW/cm~2) for various Xe mole fraction in Ar. We found that the optimum laser gas composition in our system was 0.4% Xe in Ar which was independent of the total gas pressure. At the optimum gas composition the output energy increased with increasing total gas pressure up to 16 bar, but the intrinsic efficiency reached a maximum at the total gas pressure of 8 bar. It was also found that at the optimum power deposition for both the 2.63μm and 2.65μm transitions the ratio of the integrated optical energy to that of the 1.73μm transition had a minimum in most cases at the optimum gas mixture for various gas pressures. This ratio increased with increasing gas pressure. The experimental results suggested that besides the 2-body Xe quenching at high Xe fraction and electron collision mixing at high power depositions the heavy particle quenching from Ar at high gas press     

Sheath formation study in Ne–Xe DBD discharge

The sheath is formed near the cathode immediately after applying the voltage across the electrodes. This formation is mainly due to the depopulation of this region by electrons. Using the one-dimensional model of the sheath region and the kinetic model coupled to the dielectric barrier discharge discharge electric circuit, we studied the formation of the cathode sheath and its evolution during the first pulse in Ne–Xe mixture for 10% and 20% of xenon at a total gas pressure of 400 Torr and for an applied voltage of 3 kV. The results illustrate the discharge behaviors as well as the evolution of the electric field and the charged particles in the cathode region. The effect of the xenon concentration is also studied and discussed.     

Low energy excitations in KMnO4 with 1 eV<=ΔE<=10 eV from electron-energy loss spectroscopy

Electron-energy loss spectra of potassium permanganate (KMnO₄) with primary electron energies 25 eV<=E₀<=500 eV show 7 peaks in the energy-loss range 1 eV<=ΔE<=10eV and are successfully analysed with a superposition of 7 independent Gaussians. The intensity of these lines follow roughly a power-law dependence on the primary energy I∝E ₀ ^-α . There are two groups of lines, the first with an exponent α≈0.5, while the lines in the second group decay much stronger with increasingE ₀ corresponding to a value 0.9<=α<=1.3. The 4 lines in the first group are identified as dipole allowed transitions by comparison to recent first principle molecular-orbital calculations for the (MnO₄) molecule by H. Nakai et al. The dipole-allowed excitation spectrum obtained from this analysis agrees very well with these first principle calculations.     

Wave classification and resonant excitations in lossy metal–dielectric multilayers

Loss-induced optical Bloch waves are investigated in a metal–dielectric semi-infinite multilayer placed over a substrate. In addition to the well-known classification of the electromagnetic waves into forward and backward waves, the electrostatics-based sub-classification elucidates one-level finer details of the wave nature. For this purpose, a hypothetical process is devised by continuously varying the signal velocity. As a result, a given electromagnetic wave turns out to be related to a certain electrostatic state. By this way, the metal's material loss is found to play an essential role in inducing depthwise energy flows, although it has the usual detrimental role in wave attenuation. Depending on the wave direction, normal and inverted reflection peaks on resonant excitations are illustrated.     

Geometric localization of the threshold in two-dimensional Ising ±J spin glasses forT=0

Following an approach of Toulouse, ground states in random 2D Ising ±J spin glasses (without external magnetic field), on square lattices, and with concentrations 0p0.5 of antiferromagnetic bonds are studied by means of minimal matchings of frustrated plaquettes. Lete(p) be the ground-state energy per spin in the thermodynamic limit. Then the well-known equatione(p)=–2+(p)f(p) holds, wheref(p) is the concentration of frustrated plaquettes and(p) is the average connection length between paired frustrated plaquettes in minimal matchings. Introducing (p) as the probability that a frustrated plaquette is matched to another frustrated plaquette by a connection of length (in a minimal matching), the average length(p) can be rewritten asgl(p)=(p). The study of(p) and its components (p) leads to an intervalp ^*pp ₂ (p ^*0.121±0.008,p ₂0.161±0.008) where the threshold between ferromagnet and paramagnet forT=0 lies. Analyzing a similar so-called adjoined average lengthl(p) admits further insight.     

从S(u)曲线探讨T=±OK,T=±∞K 状态的特性

本文从Ｓ（ｕ）曲线探讨Ｔ＝±ＯＫ，Ｔ＝±∞Ｋ四个极端状态的特性．文中讨论了在Ｔ＝±ＯＫ及Ｔ＝±∞Ｋ时ＧＸ＝０，因此这四个极端状态均不能作为“热库”，均无热功转换的特性，不存在包含任一状态的卡诺循环．但是却存在类似于能氏定理的ｌｉｍ（△ｓ）ｒ＝０及ｌｉｍ Ｔ＝－ＯＫ Ｔ＝＋∞Ｋ（△ｓ）Ｔ＝０的公式．本文还对研究这些极端状态的必要性与重要性进行了探讨．     

Mu l t i s i m在中学物理电学实验教学中的应用

随着计算机技术的飞速发展, 电路仿真软件已经发展为电路仿真技术的实验教学辅助手段, 运用仿真 软件辅助实验教学, 具有完整、 实用、 直观、 方便、 安全等优点, 本文通过实例展示了 Mu l t i s i m 仿真软件在中学物理 电学实验教学中的应用     

Measurement of the parity-violating longitudinal single-spin asymmetry for W± boson production in polarized proton-proton collisions at sqrt[s] = 500 GeV

We report the first measurement of the parity-violating single-spin asymmetries for midrapidity decay positrons and electrons from W+ and W- boson production in longitudinally polarized proton-proton collisions at sqrt[s] = 500 GeV by the STAR experiment at RHIC. The measured asymmetries, A(L)(W+) = -0.27 ± 0.10(stat.) ± 0.02(syst.) ± 0.03(norm.) and A(L)(W-) = 0.14 ± 0.19(stat.) ± 0.02(syst.) ± 0.01(norm.), are consistent with theory predictions, which are large and of opposite sign. These predictions are based on polarized quark and antiquark distribution functions constrained by polarized deep-inelastic scattering measurements.     

Robust estimation of excitations in mechanical systems using M-estimators—Experimental applications

This second part of the study presents some experimental applications to mechanical systems in which the results of excitation estimation, obtained using traditional least squares and M-estimate, are compared.The first case presented is a single input–multiple outputs system: a simple test-rig for the study of the vibrations of a two-degrees of freedom system is employed to identify the constraint displacement that causes the measured mass vibrations in presence of heavy noise.The second case is a multiple inputs–multiple outputs system: a rotor test-rig is used to identify the positions, the amplitudes and the phases of two unbalances using the vibrations measured in the bearings. In this case, also an additional theoretical part is introduced about the basics of model-based identification in the frequency domain applied to rotor dynamics.The last case is again a single input–multiple outputs system, but in an industrial application: experimental vibrations of a 320 MW steam turbo-generator are used to identify position and amount of a known balancing mass in an on-field real case.Moreover, whilst in the numerical examples presented in the first part the knowledge of the system was perfect, in these cases some uncertainties are present also in the system model.Finally, the paper introduces the use of the M-estimate technique to evaluate the adequacy the model of the system, by means of the analysis of the weights attributed to the measures as a function of the frequency of the excitation.     

Solitary excitations in the α-helix: Viscous and thermal effects

We report a molecular dynamics study of the propagation of a solitary excitation in a one-dimensional Lennard-Jones lattice when thermal and frictional effects are included. We give to the parameters that characterize the system the values of a typical chain of hydrogen-bonded peptide groups in the α-helix and observe that at temperatures and energies of biological interest and with water as a solvent, potential energies can be transported over long distances.