1993 Vol. 17, No. 2
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Based on the 2.5 million J/ψ's collected by the BES at BEPC,through the hadronic decay J/ψ→ωf2(1270),f2(1270)→π+π－,ω→π+π－π0,the properties of the resonance f2(1270) are studied:its mass,width,and branching ratio.the angular distribution is fitted with maximum likelihood methood,determining its.JPC=2++ and giving in the first time the helicity amplitude ratios of this process as:x=0.99±0.29; y=－0.24±0.17; z1=0.90±0.57;z2=0.56±0.22.
The spectra and decay times of a serious of Ce+3—doped BaF2 crystals have been determined.The results demonstrate that a BaF2 crystal with a proper amount of Ce+3 doped have some outstanding advantages:a near-blue fluorescence with quite fast decay time (80ns) replaces the slow component (600ns) and vary fast one (～0.8ns) of undoped BaF2.The intensity of the new component is comparable with the sum of the old ones.
We calculate the flavor-singlet axial-vector current in a quark model within pseudoscalar background-field through the Seeley-DeWitt coefficients.This current is responsible for the quark spin content of proton,and is of O(1) in the large-Ne expansion.
By considering the gab as an independent field,we have derived a covariant Polyakov string equation.The general eigenfunctions in the case of the free and fixed boundary conditions to this equation are obtained.By evaluating the trace of the fixed eigenfunctions and expanding to the leading order in 1/D expansion,we have obtained the heavy quark potential.The numerical results of ψ and γ families including energy levels,leptonic widths etc.,are in good agreement with experiment.Furthermore,we have calculated the energy levels and leptonic widths of (tt) in a wide range of t quark mass (50GeV～120GeV).
The phase structure of 3-dimensional SU(2) lattice gauge theory is studied using variational method with an independent plaquette trial action.The mean-plaquette internal energy EP～β curve is smooth,which shows only one confining phase,and is better than that given by independent link trial action.
The order parameter
The behavior of the chiral soliton model at high temperature is investigated.as well as the influence of thermal effects on the chiral soliton solutions and the fermion condensation is analysed.One possible physical mechanism is established,which is responsible for why there exists a difference between the critical temperature in deconfinement phase transition and that in chiral restoration phase transition.
Using the precise expression of electron,positron distribution function we obtained earlier,we derive the rigorous analytical expression of radiator in e+e－ collision process.This series expression converges rapidly to the precise result required.The comparison with existing approximate expression is also given.Our result benefits the precice calculation for the radiative corrections in e+e－ collision processess.
The K+N two-body potential is calculated in the framework of the constituent quark model.The derived potential includes the central and spin-orbit contributions with a simple analytic form.The K+N scattering phase shifts are calculated and compared with experimental data.The results show that the potential can provide reasonable good explanation for the K+N data,particularly for the large phase shift of P-wave I=0,J=1/2channel.
A molecular orbital theory is formulated based on α transfer for the interpretation of subbarrier fusion enhancement.The molecular potential induced by α transfer causes the enhancement of the fusion.The fusion cross section is calculated for the 24Mg+32S case.Good fits to experimental data can be reached naturally.
The projectile-like fragments emittd from 46.7MeV/u 12C induced reactions have been measured.The most probable energies of the PLFs due to the projectile fragmentation can be reproduced within the Abrasion picture.Their parallel momentum distribution widths are found to fulfill the Goldhaber relation and the extraced reduced parallel momentum distribution width σ0 is 80±10MeV/c,which is close to the value obtained in the relativistic energy region.Futhermore,the values of σ0 are the same for different reaction systems in our experiment.
Fission fragment angular distribution and angular correlation in the reaction induced by 84.0MeV 16O bombarded 238U have been measured by using two position-sensitive PPAC with large area.Transfer fission has been removed from total fission using fission fragment angular correlation technique.The contribution to the total fission cross section arising from transfer is about 10%.The anisotropy of fission fragment for transfer-fission is rather small,thus the removal of the transfer fission has little effect on the total fragment angular distribution.Indeed the anisotropy becomes larger by about 5% and anomalously anisotropies still persist.
All of the main non-perturbative results in the standard Green's function theory are obtained naturally and explicitly from the set of dynamic equations of the many-body correlation Green's functions by means of truncation up to lower correlations.The two-body correlation Green's function dynamics includes both ladder diagrams for short-range correlations and ring diagrams for long-range correlations in a unified way.
The dissipative energy,productions of subthreshold pion mesons and flowangle in intermediate-energy heavy system 86Kr+197Au reaction have been calculated by the extended BUU model,meanwhile,the relation of the energy dissipation to the charge number of PLF and the correlation of the charge number between the PLF and TLF have been reproduced.
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