中高能核物理中的几个问题

简要介绍和评述了近几年来中高能核物理中一些受关注的问题,重点介绍了核子电磁形状因子和K^-介子与原子核相互作用势强度问题。 Several problems in intermediate and high energy nuclear physics have attracted considerable attention in these years: （1） Nucleon electromagnetic form factors. There is a systematic difference between the recently measured data from high energy polarized electron-nucleon scattering experiments and the previous Rosenbluth results. （2） The strength of K^- nucleus optical potentials. It varies qualitatively from different analyyses on K^- nucleus interactions. In this paper, the above problems are discussed and reviewed briefly.     

Tracking high energy heavy-ion interactions with nuclear emulsion

EMU01 experiments tracking high energy heavy-ion interactions with nuclear emulsion detectors are performed at the BNL AGS and the CERN SPS. Some unique measurements are presented. As an illustration impact parameter selections, projectile fragmentation and particle production are discussed. Recent results from gold nucleus reactions at 11 A GeV are given.     

Application of high power lasers to the creation of active plasmas

Theoretical aspects of producing laser plasmas are considered: the characteristics of the plasma, the transfer of laser energy to the material, and the different mechanisms of heating. The high power lasers required are described. Details are given of the arrangement used at Limeil in experiments to find evidence of nuclear fusion produced by a laser beam, and some results presented. Limiting factors in the experiments are discussed.     

The relevance of HED lasers to astrophysics

The role of high energy density (HED) lasers in astrophysics is reviewed, emphasizing connections with laser physics experiments and inertial confinement fusion (ICF). Careful validation of astrophysical methods, by laboratory experiment, by critical comparison of numerical and analytical methods, and by observation are necessary for the development of simulation methods with reliable predictive capability. Recent results from hydrodynamic simulations of stellar evolution, HED laser experiments, and computer simulations will be discussed, and related to stellar evolution and supernovae.     

Fundamental Limitations and Topological Considerations for Fast Discharge Homopolar Machines

Fusion research experiments require high energy short duration pulses. A homopolar machine, as an inertial energy storage system, offers an attractive source of energy meeting these requirements. The Energy Storage Group at The University of Texas at Austin has investigated the fundamental limitations to the discharge time of homopolar machines of various topological configurations. This paper presents a mathematical model for fast discharge homopolar machines. Based on this model, various machine configurations are analyzed. A new configuration - the spool type machine - is also discussed, criteria for the evaluation of different alternatives are presented, and it is concluded that highly efficient (? 95%), high energy (? gigajoules), fast-discharge (? 5 to 30 milliseconds) homopolar inertial energy storage systems are technically feasible. Brief reference is also made to some of the experimental results obtained from the existing laboratory models.     

Hadron multiplicities

We review results on hadron multiplicities in high-energy particle collisions. Both theory and experiment are discussed. The general procedures used to describe particle multiplicity in quantum chromodynamics (QCD) are summarized. The QCD equations for the generating functions of the multiplicity distributions are presented both for fixed and running coupling strengths. The mean multiplicities of gluon and quark jets, their ratio, higher moments, and the slopes of multiplicities as a function of energy scale, are among the main global features of multiplicity for which QCD results exist. Recent data from high energy e⁺e⁻ experiments, including results for separated quark and gluon jets, allow rather direct tests of these results. The theoretical predictions are generally quite successful when confronted with data. Jet and subjet multiplicities are described. Multiplicity in limited regions of phase space is discussed in the context of intermittency and fractality. The problem of singularities in the generating functions is formulated. Some special features of average multiplicities in heavy quark jets are described.     

Lattice relaxation of graphene under high magnetic field

We investigate the n = 0 Landau level (LL) in monolayer graphene with high magnetic field. We find that the energy gap is opened in the n = 0 LL by the magnetic-field-dependent lattice relaxation originating from the interactions between the electrons (holes) and longitudinal-deformation-acoustic phonon. Both the linear and square-foot dependence of the energy gap on the magnetic field are obtained depending on the choice of the Debye cut-off wave number for the acoustic phonon. The relations of the Huang-Rhys parameter (lattice relaxation strength) and the transition linewidths with the magnetic field are also discussed. Our results agree with the current experiments on graphene in high magnetic field, and provide an alternative explanation for the experimental measurements.     

等离子体云团宽带电磁辐射源的实验研究

通过工质爆燃,产生了具有很宽频谱的电磁辐射。用4个宽带天线从不同方向对球形工质产生的电磁辐射进行了接收测量,并对信号作了频谱分析。实验结果表明:150 g工质爆炸产生的电磁脉冲持续时间为50 ns,上升沿很陡,频谱连续,频率范围为1~4 GHz,峰值频率为2 GHz,功率为2 W。对爆燃型工质产生电磁辐射的机理进行了初步理论探讨,认为等离子体辐射可能是产生电磁辐射的源。     

A search for laser heating of a sonoluminescing bubble

Thermodynamic arguments show that a sonoluminescing bubble that acts as a black body can absorb energy from a high power, pulsed laser beam. The mechanism for increasing the temperature of a sonoluminescing bubble is discussed and experiments with a frequency doubled, pulsed Nd:YAG laser are described. A bound for the amount of radiation absorbed is given as no evidence for heating was found at the low radiation intensity employed in the experiments.     

HIRFL能区与CSR能区高能γ实验

介绍了在兰州重离子加速器装置（HIRPL）上开展的原子核巨共振实验研究,并对以后在HIRFL与冷却储存环CSR上可以开展的一些高能γ实验,如双声子态实验、轫致辐射实验、集体运动消失与相变关系等作了一些讨论． The experiments on giant dipole resonance performed at HIRFL of the Institute of Modern Physics are reviewed. At HIRFL and CSR the prospective high energy gamma experiments on double phonon state, Bremstrahlung, the connection between disappearance of collective motion and phase transition, and so on, are also discussed.     

μSR and highT c superconductivity

Some implications of μSR experiments on high temperature superconductors are discussed. The possible relationship between the observation of spin freezing and the tendency of mobile holes to phase separate is considered. Measurements of the magnetic penetration depth as a function of doping are shown to imply that a non-retarded, or high energy scale pairing interaction is responsible for high temperature superconductivity. The depression of the transition temperature at high doping is associated with a crossover away from the regime in which a charge-transfer gap is relevant.     

PLASTIC SCINTILLATOR RESPONSE TO CHARGED PARTICLES

Plastic scintillators with many advantages are widely used in particle physics. Researches on plastic scintillator response at both high energy and high electric charge are significant to the experiments in high energy physics and cosmic ray physics. In addition to many important astrophysical results, the high energy cosmic rays experiments at the University of Chicago accumulate data for plastic scintillator response to relativistic particles of high electric charges. This paper introduces the cosmic ray experiments mentioned above, presents data analysis results and the discusses the nonlinear response of plastic scintillators.     

高能探测器的进展

本文综述了七十年代末以来高能探测器的进展,同时介绍了下一代高能实验给高能探测技术带来的新的挑战。     

Energy resolution of the CdTe‐XPAD detector: calibration and potential for Laue diffraction measurements on protein crystals

The XPAD3S‐CdTe, a CdTe photon‐counting pixel array detector, has been used to measure the energy and the intensity of the white‐beam diffraction from a lysozyme crystal. A method was developed to calibrate the detector in terms of energy, allowing incident photon energy measurement to high resolution (approximately 140 eV), opening up new possibilities in energy‐resolved X‐ray diffraction. In order to demonstrate this, Laue diffraction experiments were performed on the bending‐magnet beamline METROLOGIE at Synchrotron SOLEIL. The X‐ray energy spectra of diffracted spots were deduced from the indexed Laue patterns collected with an imaging‐plate detector and then measured with both the XPAD3S‐CdTe and the XPAD3S‐Si, a silicon photon‐counting pixel array detector. The predicted and measured energy of selected diffraction spots are in good agreement, demonstrating the reliability of the calibration method. These results open up the way to direct unit‐cell parameter determination and the measurement of high‐quality Laue data even at low resolution. Based on the success of these measurements, potential applications in X‐ray diffraction opened up by this type of technology are discussed.     

基于数字平板探测器的高能X射线成像实验研究

为了将数字平板探测器应用到高能X射线成像无损检测,通过实验研究了平板探测器的噪声和动态范围。设计了基于平板探测器的高能X射线成像系统。通过实验研究了电子直线加速器对数字平板探测器图像采集的束流触发同步问题。     

High temperature thermal conductivity of two-leg spin-1/2 ladders

Based on numerical simulations, a study of the high temperature, finite frequency, thermal conductivity kappa(omega) of spin-1/2 ladders is presented. The exact diagonalization and a novel Lanczos technique are employed. The conductivity spectra, analyzed as a function of rung coupling, point to a nondiverging dc limit but to an unconventional low frequency behavior. The results are discussed in perspective with recent experiments indicating a significant magnetic contribution to the energy transport in quasi-one-dimensional compounds.     

Photofission with linearly polarized photons

The formalism for fragment angular distributions in photofission with unpolarized and linearly polarized photons is summarized. First experiments on²³²Th using linearly polarized bremsstrahlung are described. The results for the analyzing power show for the first time in a model independent way that the low energy photofission can be explained byelectric dipole excitation. The possibilities of this new method are discussed, in particular when using monoenergetic tagged photons, which are available soon at new high duty cycle electron accelerators.     

相对论粒子的散射与低速粒子的散射

研究了相对论粒子间散射的规律,推导了相对论粒子间散射的洛伦兹因子公式.结果发现:如果两个粒子的静止质量相同,则粒子在高速时的碰撞规律和低速时的碰撞规律相同,即两个正碰粒子互换速度;如果两个粒子的静止质量不同,则粒子在高速时的碰撞规律和低速时的碰撞规律不同,高速正碰时重粒子将损失大部分能量,轻粒子的速度将接近光速,而不等于重粒子速度的2倍.     

Working group report: Neutrino and astroparticle physics

This is the report of neutrino and astroparticle physics working group at WHEPP-7. Discussions and work on CP violation in long baseline neutrino experiments, ultra high energy neutrinos, supernova neutrinos and water Cerenkov detectors are discussed.