2000 Vol. 24, No. 3
A convenient generator, based on the existing framework of BES simulation, applicable generally to both ψ′ and J/ψ decays of VP and PP modes, is established. The corresponding angular distribution is taken into account. A similar generator is also established for the successive J/ψ decay in the process of ψ′→X+ J/ψ. In the measurement of branching ratios for ψ'→γη, γη′, ωπo, π+π－, K+K－, this generator is used to determine the selection efficiency and estimate the background.
The data of radiative decays involving η, η′ and their two-photon decay process and some electromagnetic processes of the J/ψ-P+V (Pseudoscalar and Vector mesons) have been used to study the admixture of pseudoscalar mesons η,η′ and non-qq isoscalar flavor singlet (such as ι/η (1440)). The "mixing parameters of two schemes are fitted by using the method of least Squares. If we only consider the mixing of η and η′ the fitting result is not good. If the admixture of η, η′ and the non-qq mesons (represented by ι later on) has been considered the result is better. The conclusion is that the η′ may contain a few non-qq component and ι has some qq component.
The neutrino and antineutrino deep inelastic scattering of unpolarized and polarized A and A productions can provide a clean separation of unpolarized and polarized fragmentation functions of a quark into a A, for both light-flavor quarks and antiquarks and also for strange quarks. One can systematically measure or check the various flavor and spin dependent fragmentation functions by combining with A and A productions in polarized electron deep inelastic scattering. Such measurements can provide crucial tests of different predictions concerning the spin structure of hadrons and the quark-antiquark asymmetry of the nucleon sea.
By using the coordinate Bethe ansatz method, we obtain the exact solution of generalized t-J model. It is shown that the scattering matrix for two-body scattering is trigonometric non-symmetry 6-vertex R-matrix.
A simple and effective scheme for improving the lattice Hamiltonian in 1+1 dimensional QCD is given. The large Nc behavior of the vector meson mass in the chiral limit is studied by using this improved scheme. This numerical result is consistent with the analytical strong coupling result.
High spin states in 87Zr was studied through the fusion evaporation reaction 59Co(32S, 3pn)87Zr at a beam energy of 118 MeV using in-beam r-my spectroscopic method.r-r coincidence measurement was performed by using an array consisting of seven antiCompton spectrometers, and DCO ratios of some r rays were determined. The level scheme of 87Zr wasestablished up to spin (37/2+) and (43/2－). Many previously unknown states have been observed. Comparison with neighboring isotones indicates that effect of neutron on nuclear structure property is predominant compared to proton, and there is a tendency of reduction in band crossing frequency with increasing proton number.
A hadron and string cascade model, JPCIAE, which is based on LUND string model, PYTHIA event generator especially, is used to study the photon production of 200 A GeV S + An central collisions. The model takes into account photon produced from the partonic QCD scattering processe, the final-state hadronic interaction, and hadronic decay and deals with them consistently. The results of JPCIAE model reproduce successfully the WA93 data of low PT enhancement. We have compared the contributions from different decay channels and discussed the role played by rescattering.
Baed on the BUU Model, the equilibrium process has been discussed in intermediate energy heavy ion collision, and some related physical quantities, collective flow, temperature and chemical potential have been discussed. Through our studies, we have found that the local equilibrium reaches at a certain time step. The local equilibrium begins from the central region. And for the peripheral collision, the local equilibrium has also been obtained. The temperature and chemical potential for the equilibrium is 5一7MeV and 30MeV, respectively.
The recently proposed FST model with chiral symmetry is used to study the incompressibility of nuclear matter at both zero and finite temperature. The results are compared with those from other models and experiments.
Within the framework of an IQMD model, multifragmentation in reactions of 112Sn+112Sn and 124Sn+124Sn at 40MeV/u is investigated. The calculated results are in qualitative agreement with the experimental data. Sighficantly different scalings of the mean IMF multiplicties with neutron, charged-particle, light charged-particle multiplicities, and Zbound are observed for the two reactions. In addition, Comparing with the results of expanding evaporating source model and an isospin-dependent percolation model, it is found that the isospin dependence of multifragmentation mainly results from the isospin dependent reaction dynamics.
The influence of isospin effects on the multifragmentation in the head-on collisions of the system 40Ca+40Ca and 40Ar+40Ar for different incident energies is discussed by using isospin dependent quantum molecular dynamics model (IQMD). It is found that the intermediate mass fragment (IMF) has obvious difference at high incident energy, because the nucleon-nucleon cross section effects is major in the process of heavy ion collision. Thus, we have some opportunities to extract the information of nucleon-nucleon cross section. At low energy various isospin effects affect each other, resulting in no obvious difference in the IMF between two systems.
The Lattice Gas Model is essentially intrduced to describe the features of isospin effect on the yield of ho particles,their ratios and double isotopic ratios. Calculations show that the multiplicity of light particles is consistent consistent the systematics of isospin. Moreover,the isotopic yield ratios are in accordance with N/Z of the system. With the increasing of (N-Z)/A, the isotopic ratios decrease,but double isotopic ratios display their insensitivity to isospin.
The systematics of the isovector Giant Dipole Resonance is studied via the microscopic semi-classical Vlasov method. The Woods-Saxon potential is used in the calculation with the different parameters for neutron and proton, respectively. It is found that the peak energies of the GDR strength distribution follow the empirical formula and agree with the experimental data. The GDR widths agree with the experimental data in the error bar. On the basis of these studies, we have investigated the GDR properties of Ca isotopes and three isomers with mass number A=40, 100 and 208. The studies show that the effects of isospin on the peak energies of the GDR strength distribution are small, Which rise slowly with the increase of (N-Z)/A. The isospin effects on the GDR width are not observed.
With the recent research progress of RFQ, the upper limit of RFQ's working frequency is expected to be put upward in proton accelerator for medical application. The main parameters of a 714-0. 8MeV RFQ are discussed and then checked with PARMTEQ. The multiparticle simula- tion results indicate that RFQ will work properly in such relatively higher frequency.
The E2 transition r-ray energies and the dynamical moment of media of the six superdeformed (SD) bands in 148Gd have been investigated by use of the rigid-rotor with the q-deformed moment of media. The calculated results coincide with experimental data. It indicates that the approach of rigid-rotor with the q-deformed moment of inertia may be powerful in description for hath the yrast SD band and the excited bands simultandously.
The negative correlation in W+W－ hadronic decay, which has recently been proposed as a possible signal for the colour reconnection in these proceses, is studied in some detail by using the random cascadingα-model. The effect of colour reconnection is modeled by the particle exchange between two final state systems forming from two W's. The negative correlation given by Pythia event generator is recovered in this way, providing a physical picture for this effect.
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