π－π－ Bose-Einstein Correlation at AGS Energies

The study of Bose-Einstein correlations between two identical particles offers a powerful probe to the space-time evolution of ultrarelativistic nucleus collisions.We calculate the correlation function of π^－π^－ due to the four space-time and four-momentum distributions of π-at freeze-out in hadronic cascade simulation of ²⁸Si(14.6 A GeV/c)+Au reactions.The correlation function calculated by Fourier transformation method,the correlation function resulted from fullcalculation and the corresponding experimental correlation function agree each other very well.The above freeze-out configuration of π^－ is also used to calculate the root mean square length of π^－ source.These lengths are compared with the conventional fitted radius parameters of source.     

Study of J/ψ、γπ0π0 at BES

The decay J/ψ→γπ⁰π⁰ is studied with 7.0×10⁶ produced J/ψ events collected by the Bening Spectrometer(BES) with the tugger mode senseuve to both chmped and neutral final state at the Bening Electron-Positron Collider(BEPC), The evidences for the existence of f_J(1710) and E(2230) in this channel are presented, and the corresponding masses as wen asthe product branching ratios are obtained.     

Branching Ratios of J/ψ→π03(π+π－)

The decay mode of J/ψ→π⁰3(π⁺π^－) was studied very little before. There are no informations except branching ratios for this channel in PDG book which based on less than 0.2×10⁶J/ψ events of MARKⅠ. Now, BESⅠ has a data sample of 7.8×10⁶J/ψ events, we can make more accurate results than MARKⅠ. Total of 3290±43 J/ψ→π⁰3(π⁺π^－) events including 1275±86 J/ψ→ω²(π⁺π^－) events are selected. J/ψ→π⁰3(π⁺π^－) and J/ψ→ω²(π⁺π^－) events have been generated with MC simulition for calculating events selection efficiency. BESⅠ result is: Br(J/ψ→π⁰3(π⁺π^－))=(2.52±0.06±0.43)% and Br(J/ψ→π⁰3(π⁺π^－))=(1.31±0.09±0.21)%. Meanwhile, we studied the invariant mass of 4π and ωππ to find interesting signals. It seems that there is a peak at about 1.74GeV in the invarianat mass spectrum of 4π, and a enhancement was also found at about 1.9GeV in the invariant mass spectrum of ωππ. It is not clear whether they are from resonances or background. Therefore, more work in detail is still going on.     

Measurement of the τ Polarization Asymmetry in τ→a1 v→π±π0π0v Decay at Z0 Peak

The τ polarization asymmetry in τ→a₁v→π^±π⁰ π⁰v decay at Z⁰ peak is measured using data collected by L3 detector at LEP in 1992 and 1993, A_pol=－0.239±0.126±0.100, where the first error is statistical and the second systematic. And the effective electroweak mixing angle sin²θ_w=0.2197±0.0219 is derived.     

Decay of the J/ψ to Σ0Σ0 Final State

With 7.8 million produced J/ψ events collected by the BES detector at the BEPC, the decay J/ψ→Σ⁰Σ⁰ is analysed. The branching ratio is measured to be BR(J/ψ→Σ⁰Σ⁰)=(0.97±0.04±0.24)×10^－3. The angular distribution is of the form dN dcosθ=N₀(1+α cos²θ) with α value of －0.21±0.27±0.13.     

Glueball Masses of the 0++ and 0－－ in 3+1-D SU(3) LGT

We improve the coupled cluster method in lattice gauge theory based on the application of the random phase approximation. Using this method, we study the vacuum wavefunction and glueball mass of the 0^－－ and 0⁺⁺ in 3+1 D SU (3) lattice gauge theory by finding the solution of the Hamiltonian eigenvalue equation. The calculated results are satisfacting γ=m (0－－)/m(0++)=1.8578±0.0506.     

A Study of the Processes of e+e－→e+e－,μ+μ－ at Large Angle and Measured Luminosities

Using the BES data collected at √S=4.03GeV.the QED processes of e⁺e^－→e⁺e^－,μ⁺μ^－ have been studied. Our measurements agree with the QED prediction,and luminosities obtained from these two final states are compatible at a level of 4%.The total integrated luminosity of 23.1pb^－1 was given for all data collected at this energy region from the calculation.     

π－核双电荷交换反应核谱因子和26Mg(π+, π－)26Si反应

π^－核双电荷交换反应的强度与反应过程的两核子转移的核谱振幅直接联系着. 本文讨论了这类反应与它们的核谱因子的关系. 并以²⁶Mg(π⁺, π^－)²⁶Si为例, 用两种核结构讨论了它的激发函数和微分截面. 我们所用的理论方法能够解释实验数据.     

从KL0产生（π±μ干）原子

本文求解了自旋是0-1/2的不等质量的库伦原子的Bethe-Salpeter方程。应用所求得的近似的B-S波函数以及近年来发展的复合粒子量子场论微扰展开理论计算了由K_L⁰产生（π^士μ^干）原子的几率。     

Radial Equation of Bound State and Binding Energies of Ξ－ Hypernuclei

The radial equation in its standard form, which can be solved by using the threepoint central difference method from central two points towards outside point by point, is reduced from Schrodinger equation or from the low energy approximation of Dirac equation. In this paper, a method for solving the radial equation of the bound state to get the binding energy and the radial wave function is given, and the binding energies of the ground state (GS) of several Ξ^－ hypernuclei are calculated.     

μ－ CAPTURE IN NUCLEI

Using the many-body field theory the problems of μ^－ captures in nuclei are systematically studied.Without ajustable parameter,calculations are performed for the total nuclear capture rates of muon for nuclei ranging from light to heavy ones.It shows that the renormalization due to the spin-isospin-dependent strong interaction and the muon binding in the μ^－ atom are essential for a thorough understanding of this type of weak interaction processes.     

Search for the Decays D+→φe+ν,D+→φK－π+e+ν,D0→φK－e+νand D0→φK－μ+ν

We report the results of a search for the semileptonic decays D⁺→e⁺ν,D⁺→K^－π⁺e⁺ν,D⁰→K^－e⁺ν and D⁰→K^－μ⁺ν using the BES detector at the BEPC e⁺e^－ Collider. Using a data sample of 22.3pb^－1 collected at the center of mass energy s=4.03GeV, we select 2472±87D 0 tag DX and 7628±149D 0 tag DX singly tagged D events, where the X could be γ, π 0 and/or π^±. Based on the method of "combined D⁺and D⁰ single and double tags", we determine that 2471±218 D⁺X and 7629±251 D⁰ X are contained in the recoil side of the singly tagged neutral and charged D mesons, respectively. No events for the 4 semileptonic decay modes are observed in the recoil side of the tagged D mesons. The 90% confidence level upper limits of B(D⁺→e⁺ν)<1.38%,B(D⁺→K^－π⁺e⁺ν)<2.01%,B(D⁰→K^－e⁺ν)<0.53% and B(D⁰→K^－μ⁺ν)<0.53% are determined from the search for the semileptonic decays of D⁺ and D⁰.     

Study of D0→π－l+νl Decay

In this paper, the D⁰→π^－l⁺ν_l decay process is studied by applying light-cone QCD sum rules. The form factor of D→π transition is calculated by choosing a correlation function with a chiral current to eliminate the effect caused by the uncertainty of the twist-3 function of the pion. Therefore the calculated result of the form factor is improved, and the branching ratio of the D⁰→π^－l⁺ν_l decay process is consistent with the new experimental data.     

Study on Stiffness of the Symmetry Energy at High Densities by π－/π+ Ratio

using the isospin–and momentum–dependent transport model, for three different symmetry energies, we have calculated the π^–/π⁺ ratio as a function of time and tranverse–momentum in central 132sn+124 sn collision at e_beam/A=400mev. the results show that the π^–/π⁺ ratios is very sensitive to the stiffness of the symmetry energy. thus we can probe the stiffness of the symmetry energy at high densities by using the π–/π+ ratio at different time or transverse momentum more accurately than before. comparing experimental data with the calculations will reveal crucial information about the stiffness of the symmetry energy more accurately.hadronic transport model, symmetry energy, π–/π+ ratio     

Analytic Approximation for Process e++e－→τ++τ－ Cross Section Near Threshold

In the structure function approach,we calculate the threshold behaviours for e⁺+e^－→τ⁺+τ^－,which including QED radiative corrections from initial correction,vacuum polarization effect,Coulomb effect and final state correction.This theoretical prediction for threshold behaviours of τ-pair production is useful for BES new measurement of lepton τ mass.     

Three Body Amplitude Analysis of the Process a2(1320)→π+π+π－

We analyze the decay amplitudes of the process a₂(1320)→π⁺π⁺π^－ using the tensor analysis method and show how to obtain three body amplitudes.     

D0-MESON DECAYS Γ（D0→K+K-）/Γ（D0→π+π-）

In this paper the nonleptonic D⁰-decays are discussed. Using Gilman and Wise's methods, we derived the effective Hamiltonian for Cabibbo-suppressed nonleptonic D^0*-decays. The rate F(D⁰→K⁺K^-)/Γ(D⁰→π⁺π^-)～1.26 is obtained. Some problems in this method of the calculations are discussed roughly.     

Searching for new physics in D0→μ+μ-, e+e-,μ±e干 at BES and/or the super charm-tau factory

In contrast with B⁰-B⁰, B_s-B_s mixing where the standard model (SM) contributions overwhelm that of the new physics beyond standard model (BSM), a measured relatively large D⁰-D⁰ mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D⁰→μ⁺μ^- could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D⁰. Concretely we discuss the contributions of unparticle or an extra gauge boson Z' while imposing the constraints set by fitting the D⁰- D⁰ mixing data. We find that the long-distance SM effects for D⁰→l1 still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D⁰→μ^±e⁺, the new physics contribution would be significant.     

Multi-channel Coupling in the Hadronic Decay Process J/ψ→ωπ+π－

The coupling problem of the three different intermediate processes J/ψ→ωf₂(1270),f₂→π⁺π^－ and J/ψ→b₁^±(1235)π⁺,b₁^±→ωπ^± included in the hadronic decay process J/ψ→ωπ⁺π^－ is discussed.The consideration of the coupling effect is very important for measuring the parameters of the resonances f₂ and b₁^± and the helicity amplitude ratios of these reactions precisely.     

D介子衰变Γ（D0→K+K-）/Γ（D0→π+π-）

考虑强作用修正对D⁰介子衰变的影响,用Gilman和Wise^[1]的方法,导出ΔC=1的等效哈密顿量,算得Γ（D⁰→K⁺K^-）/Γ（D⁰→π⁺π^-）～1.26,简单讨论了这种计算方法中的一些问题。