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.     

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.     

Observation of a pp mass threshold enhancement in ψ′→π+π－J/ψ(J/ψ→γpp) decay

The decay channel ψ′→π⁺π^－J/ψ(J/ψ→γpp) is studied using a sample of 1.06×10⁸ ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the pp invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M=1861⁺⁶_－13 (stat)⁺⁷_－26 (syst) MeV/c² and a narrow width that is Γ<38 MeV/c² at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons.

     

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.     

Helicity Formalism of the Angular Distributions for the Process e++e－→J/ψ→V+X,X→3P

The helicity formalism of the angular distributions for the process e⁺+e^－→J/ψ→V+X,X→P₁+P₂+P₃(V and stand for vr and psealar meson, respectvely) are given in this paper. It provides the theical formula for determining the spin and parity of the intermediate state X of the above process.     

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.     

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.     

First Evidence of ψ(3770) Hadronic Transition to J/ψπ+π—

Evidence of ψ(3770) decays to a non-DD final state is observed. A total of 6.8±3.0 ψ(3770)→J/ψ→π⁺π^— events are obtained from a data sample of 8.0±0.5 pb^-1 taken at center-of-mass energies around 3.773GeV using the BES-Ⅱ detector at the BEPC. The branching fraction is determined to be BF(ψ(3770)→J/ψ→π⁺π^—)=(0.59±0.26±0.16)%, corresponding to the partial width of Γ(ψ(3770)→J/ψπ⁺π^—)=(139±61±41)keV.     

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.     

Color Rearrangement in e+e－→W+W－→h's Process

The probability of Color Rearrangement at partonic level in e⁺e^－→W⁺W^－→h,s process is studied using the Color Effective Hamiltonian. The comparison between our results and those of Gutafson and Sjostrand et al. is also given. It is found that this probability cannot be neglected, and it is pointed out that to investigate the Color Rearrangements, the hadronization models should be developped and improved.     

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 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.     

Hadronic Transport Model Explanation of K+/π+ Ratio in Relativistic Nucleus-nucleus Collisions

We propose a simple hadronic transport model for investigating the K⁺/π⁺ ratio in relativistic nucleus-nucleus collisions and point out that the thermal motion of baryons and multiple rescattering effect play an important role in the enhancement of K⁺/π⁺ ratio.The experimental data of enhancement of K⁺/π⁺ ratio could be explained within a reasonable temperature parameter (～150MeV).     

强子衰变过程J/ψ→ωπ+π－中的多道耦合

讨论了强子衰变过程J/ψ→ωπ⁺π^－包含的三个不同中间过程J/ψ→ωf₂(1270),f₂→π⁺π^－和J/ψ→b₁^±(1235)π⁺,b₁^±→ωπ^±的耦合问题.这种耦合效应的考虑对于精确测定共振态f₂和b₁^±的参数以及这些反应道的螺旋度振幅比是十分重要的.     

Formalism of Helicity Coupling Amplitudes for J/ψ→π+π-π0

The formalisms of helicity coupling amplitudes for J/ψ→π^＋π^-π^0 are presented. A detailed discussion is also given on the barrier factor, Breit Wigner, and density matrix. A Monte Carlo simulation of J/ψ→ρ（770）π→π^＋π^-π^0 is carried out. The results show that the p（770） resonance is well reproduced compared with experimental data.     

Determination of J/ψ Leptonic Branching Fraction Via ψ(2S)→π+π－J/ψ

Two processes ψ(2S)→π⁺π^－J/ψ,J/ψ→1⁺1^－ and J/ψ→anything are carefully studied to get the J/ψ leptonic branching fractions with the ψ(2S)data at BES/BEPC.The results are B(J/ψ→e⁺e^－)=(5.90±0.07±0.16)% and B(J/ψ→μ⁺μ^－)=(5.96 ±0.08±0.16)%,and B_e/B_μ is estimated to be 0.990±0.018±0.024.Assuming B_e=B_μ,the leptonic branching fraction of the J/ψ is B(J/ψ→1⁺1^－)=(5.93±0.05 ± 0. 16 )%.This result is used to estimate the QCD scale factor ∧(nf/MS) and the strong coupling constant α_s.     

Probe the Strength of Annihilation In BS→π＋π－ Decays Within QCD Factorization

Using the method of QCD factorization, we calculate the branching ratio and the CP violation for pure annihilation decay B_S→π^＋π^－ in the Standard Model. Meanwhile, we employ an effective gluon mass resulted in the study of the infrared behaviour of gluon propagators to avoid the soft endpoint divergence. We find that the CP-averaged branching ratio is about 1.24×10^－7, and the penguin diagram contributions is dominant in this process. The direct CP violation parameter is about －0.05, while the mixing-induced CP asymmetry is a quite large number of 0.18. Once these quantities can be measured in the future LHC-b experiments, studying such a process will enrich our knowledge on the dynamics of the charmless hadronic decay of B-meson and the property of gluon.     

Study on the Baryon State X Produced in the Process J/ψ→p+X,X→Δ+π

The existence of the new class of hadronic states, glueball, hybrid mesons and hybrid baryons, is one of the important prediction of the QCD. It is an excited and attractive research preject to search for and identify these non-qq meson and non-qqq baryon states. The theoretical expectations on the mass spectrum of hybrid baryons have been carried out in the bag model, QCD sum rules and flux tube model. We might expect that J/ψ hadronic decay processes are the good place to study hybrid baryons. The J/ψ decay process J/ψ→p+X,X→Δ+π, where p and Δ are the antiproton and Δ baryon with spin parity (3/2)⁺, respectively, are studied in terms of the angular distribution and the generalized moment analysis methods. Precise angular distribution and moment representation of baryon resonance (including the hybrid baryon) X with spin parity (1/2)^±,(3/2)^±,and (5/2)^± are obtained. They can be used to identify the spin of the baryon resonance state X.     

J/ψ→ωπ+π-衰变道中σ粒子存在的证据

基于BESⅠ的7.8×106的J/ψ数据样本,研究了J/ψ→ωπ+π-衰变. 在反冲ω粒子的π+π-的不变质量谱中清楚地观察到了一个低质量端的突起,此突起既不来自相空间效应,又不来自本底. 根据分波分析,此低质量端的突起是一个0+ +的共振态,即σ粒子. 如果用常数宽度的Breit-Wigner函数来拟合σ粒子,其质量和宽度分别为384±66MeV和458±100MeV,与其对应的极点位置是(434±78)-i(202±43)MeV.     

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.