中能区反质子与核的非弹性散射

运用多次散射理论的光学势获得反质子的扭曲波.在扭曲波冲量近似下,讨论了中能区反质子与原子核的非弹性散射.考虑了反质子能量从180MeV到1800MeV这一能区¹²C,的2+,3-态微分截面.在这一能区的低能端,(E=180MeV)DWIA能够很好的符合实验,同时,预示了更高能量可能出现的微分截面的理论结果.     

中能区反质子与核非弹性散射的自旋效应

运用多次散射理论获得中能区的反质子光学势.这一光学势扩大到包含自旋轨道耦合项,并用它求得反质子的扭曲波.在扭曲波冲量近似下,讨论中能区反质子与原子核非弹性散射的微分截面和极化度.计算反质子能量从180-508MeV间12C12C的2+,3-态的和Pf(θ).在低能端理论结果 能够很好的符合 实验.同时预言了更高能量下可能出现的 和Pf(θ)的理论结果.     

Antiproton-Nucleus Interaction and Coulomb Effect at High Energies

The Coulomb effect in high energy antiproton-nucleus elastic and inelastic scattering from ¹²C and ¹⁶O is studied in the framework of Glauber multiple scattering theory for five kinetic energies ranged from 0.23 to 1.83 GeV. A microscopic shell-model nuclear wave functions, Woods-Saxon single-particle wave functions, and experimental pN amplitudes are used in the calculations. The results show that the Coulomb effect is of paramount importance for filling up the dips of differential cross sections. We claim that the present result for inelastic scattering of antiproton-¹²C is sufficiently reliable to be a guide for measurements in the very near future. We also believe that antiproton nucleus elastic and inelastic scattering may produce new information on both the nuclear structure and the antinucleon-nucleon interaction, in particular the p-neutron interaction.     

Coulomb Effect on Inelastic Scattering of Proton on Deformed Nuclei at High Energies

In this paper, by using the collective coordinate of A. Bohr and phenomenological deformed optical potential and Coulomb interaction, the scattering amplitude of two composite particle systems can be obtained. The differential cross sections for the 0⁺, 2⁺, 4⁺ and 6⁺, p(0.8 GeV)+¹⁵⁴Sm and p (0.8 Gev)+¹⁷⁶Yb are calculated. The results show that the Coulomb effect is quite important.     

Positron-Lithium Atom and Electron-Lithium Atom Scattering Systems at Intermediate and High Energies

The coupled-channel optical method is used to study positron scattering by atomic lithium at energies ranging from the ionization threshold to 60eV, The present method simultaneously treats the target channels and the positronium （Ps） channels in the coupled-channel method together with the continuum effects via an ab-initio optical potential. Ionization, elastic and inelastic cross sections in target channels, and the total cross section are also reported and compared with other theoretical and experimental data. A comparative study with the corresponding electron-lithium data is also reported.     

The Spin Effect of Antiproton-Nucleus Inelastic Collison

If the antiproton optical potential is inclusive of the spin orbit interaction term,the A(p,p)A* inelastic scattering not only can excited the normal parity states,but also can excited the abnormal parity states.There are also induced the polarization P_f(θ) at the inelastic scattering.In the framework of DWIA,we derived the inelastic scattering cross section (dσ/dΩ)_f,i,and polarization P_f(θ),and calculated the (dσ/dΩ)_f,i, and P_f(θ) for ¹²C(p,p)¹²C* with 2⁺,3^－ and 1⁺ states at antiproton energies of 46.8 and 179.7MeV.They fited experiment data quite well.Due to the abnormal partity states in the inelastic process have been measured,the spin orbit term can not be neglect.     

Pion-Nucleon Scattering Experiments at Low Energies

Pion-nucleon scattering and charge-exchange experiments aim at a determination of the pion-nucleon coupling constant, the sigma term of chiral symmetry breaking in non-perturbative QCD and the possible isospin breaking of strong interactions. A review of the present situation shows that the accuracy of the results is still limited by the existing data base despite 20 years of experimental efforts at meson factories. The present new generation of experiments at PSI and TRIUMF, using novel instrumentation, promises considerable progress.     

低能反质子的核散射与Glauber理论

运用Glauber多次散射理论,分析低能量反质子与⁴He核的弹性散射微分截面的实验结果.看到反质子能量低到19.6MeV时,多次碰撞的特征仍然是主要的.用光学模型的计算和比较,也得到相同的结论.     

Antiproton-Nucleus Scattering in a Hybrid Quark-Hadron Model

A hybrid quark-hadron model is used to describe high energy antiproton-nucleus scattering. The parameters for the quark regime are determined by fitting antiproton-proton elastic scattering data.     

Complete Set of Deuteron Analyzing Powers for dp Elastic Scattering at Intermediate Energies and Three Nucleon Forces

With the aim of clarifying roles of the 3NFs in nuclei experimental programs with the polarized deuteron beam at intermediate energies are in progress at RIKEN RI Beam Factory. As the first step, we have measured a complete set of deuteron analyzing powers in deuteron–proton elastic scattering at 250 and 294 MeV/nucleon. The obtained data are compared with the Faddeev calculations based on the modern nucleon–nucleon forces together with the Tucson–Melbourne’99, and UrbanaIX three nucleon forces.     

Dielectron Production in Pion-Nucleon Reactions at Intermediate Energies

Dielectron production in the πN interaction at not large energies is studied assuming that the electron- positron pair is produced from splitting of the virtual time-like photon. It allows us to get the interesting information on a nucleon form factor in the time-like region of four momentum transfer squared. The dominant contribution of the Δ-isobar creation in the intermediate state at incident pion momenta of about 0.3–0.4 GeV/c is shown. The experimental distributions over the angle and effective mass \({M_{{e^ + }{e^ - }}}\) of the e⁺e^? pair are described satisfactorily. This stimulated us to present theoretical predictions for the \({M_{{e^ + }{e^ - }}}\) distribution in the process π^?p → ne⁺e^? at different incident momenta, which could be verified, for example, by the HADES experiments.     

Experimental Studies of Few-nucleon Systems at Intermediate Energies

Systems composed of 3 nucleons are a subject of precise experimental studies for many years. At the first stage the investigations were mainly focused on elastic nucleon-deuteron scattering, slowly extending to systematic measurements of the deuteron breakup reaction. Intermediate energies, below the threshold for pion production, deserve special attention: it is the region where comparison with exact theoretical calculations is possible, while the sensitivity to various aspects of interaction, like subtle effects of the dynamics beyond the pairwise nucleon-nucleon force, is significant. Moreover, the Coulomb interaction and relativistic effects show their influence in the observables of the breakup reaction. All these effects vary with energy and appear with different strength in certain observables and phase space regions, what calls for systematic investigations of a possibly rich set of observables determined in a wide range of energies. The next step in complication of the system are studies of reactions involving 4 nucleons—more sensitive, as expected, to subtle dynamics beyond the pairwise interaction. A brief survey of recent and planned experiments in the 3- and 4-nucleon systems is given.     

中能重离子碰撞中K介子产生动力学研究(英文)

基于兰州量子分子动力学(LQMD)模型研究了阈能附近K介子(K0和K+)产生动力学机制。LQMD模型能够较好地描述中能重离子碰撞中K介子产额分布。通过拟合K介子动能谱分布,计算中采用了排斥的K-核子相互作用势。该光学势增强了高动量K介子产生,而降低了K介子总产额。结合实验数据比较,在高密区域给出了较软的对称核物质状态方程。对称能的软硬对K0/K+比值起着重要作用,特别是在阈下区域。而K介子光学势对K0/K+比值激发函数影响不明显。     

Study of Kaon-Proton Elastic Scattering at High Energies

It ia shown that the differential cross section for both K⁺p and K^-p elastic scattering including the most recent measurements for 20 < pL < 200 (GeV/c) and with -t extended upto 28 (GeV/c)² can be fitted by using the pomeron as dipole and p as a simple pole. The difference of the total cross section for K⁺p and K^-p scattering is also explained.     

Virtual Compton Scattering off Spin-Zero Particles at Low Energies

We discuss the low-energy behaviour of the virtual Compton scattering amplitude off a spin-zero target. We first compare various methods of obtaining a low-energy expression based either on the soft-photon approximation or the use of Ward-Takahashi identities. We point out that structure-dependent terms are defined with respect to a low-energy approximation of the pole terms, which commonly is separated from the full amplitude. We derive a general expression for the structure-dependent terms in an expansion in terms of the momenta and of the initial and final virtual photon, respectively, up to and including terms of order . At order two terms appear that are related to the usual electric and magnetic polarizabilities of real Compton scattering. At order we find nine new structures of which five can only be determined using virtual photons. Received October 23, 1997; accepted for publication December 29, 1997     

On Timelike Compton Scattering at Medium and High Energies

We emphasize the complementarity of timelike and spacelike studies of deep exclusive processes, taking as an example the case of timelike Compton scattering (TCS) i.e. the exclusive photoproduction of a lepton pair with large invariant mass, versus deeply virtual Compton scattering i.e. the exclusive leptoproduction of a real photon. Both amplitudes factorize with the same generalized parton distributions (GPDs) as their soft parts and coefficient functions which differ significantly at next to leading order in α _s . We also stress that data on TCS at very high energy should be available soon thanks to the study of ultraperipheral collisions at the LHC, opening a window on quark and gluon GPDs at very small skewness.