1995 Vol. 19, No. 8
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The cross sections of e+e－→hadrons,e+e－,μ+μ－have been measured in the vicinity of J/ψresonance at BES/BEPC.The fit of the observed cross sections gives the new results of J/ψ resonance parameters:the partial widths to hadrons,electrons and muous are Γh=74.1±8.1keV,Γe= 5.14±0.39keV and Γμ=5.13±0.52keV respectively;the total width Γ=84.4±8.9keV;the branching fractions Γh/Γ=(87.8±0.5)%,Γe/Γ=(6.09± 0.33)%,and Γμ/Γ=(6.08±0.33) %.
By using 28MeV/u 18O beam,an on-line melting lead target equipment and 4π-ΔEβ-γcoincident technique,the relative cross section ratios and absolute cross sections of neutron-rich nuclides 205—208Hg have been measured. The production cross section of 209Hg is extrapolated.The cross section of 207Hg produced by-2p +1n from target decreases suddenly,which may be explained by change of reaction Q value.
The identification of tau one prong hadronic decay using neural network is presented.Based on the identification,we measured the branching ratios: Br(π/Kv)=(12.18±0.26±0.42)%,Br(π/Kπ0v)=(25.20±0.35±0.50)%,Br(π/K2π0v)=(8.88±0.37±0.38)%,Br(π/K3π0v)=(1.70±0.24±0.39)%.
Nuclear interactions induced by 10.7A GeV 197Au-ions at BNL/AGS are studied and the recent results on projectile nuclear fragmentation and particle production from the EMU-01 experiment are presented.
The two-loop effective potential of the non-topological soliton bag model at finite temperature and finite density is calculated.The influence of thermal effects on the vacuum structure is investigated as well.
The fourth rank polarization tensor and the helicity amplitudes of γ-γ scattering via charged scalar meson loops in some non-standard models are calculated.They are expressed precisely and analytically in terms of three transcendental functions of B(u),T(u) and I(u,v).
The irreducible representations of Brauer algebras are constructed using an induced representation method.A dimension formula for calculating the irreducible representations of Brauer algebras is derived.
The correlation functions of relative angle distributions of mass-symmetric ternary fissions in the reactions Ar+Au、Bi、Tb at 25MeV/u are presented.The evolution of decay mode of hot nucleus is studied by comparing the present data with Ar+ An(60MeV/u)experimental results.It is shown that the time scale for fragment emission is reduced from the characteristic timeτ=1000fm/c at 25MeV/ufor standard sequential decay to prompt emission one at 60 MeV/u withτ=50 fm/c.
By employing the heavy quark effective theory,the spectra of heavy hadrons.such as heavy mesons (q),heavy baryons(QQq and Qqq)and heavy multiquark systems(qq)are studied systemically.The results are compared with the predictions for qq in potential model.
The probability distribution and the entropy of 208Pb nuclei under different excited energies are calculated.Comparison is made between the probability distributions and the entropies with time for different excited energies.The result shows that our previous calculation is reasonable.
The analytical calculation of the nuclear ground state deformation of the eveneven isotopes in the rare-earthregion is given by utilizing the intrinsic states of the sdg interacting boson model.It is compared systematically with the reported theoretical and experimental results.It is shown that the sdg interacting boson model is a reasonable scheme for the description of even-even nuclear deformation.
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