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.     

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.     

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.     

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.     

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.     

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.     

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.     

Measurement of Structure Function of τ→π±2π0v

The structure function of τ→π^±2π⁰v is measured by model independent method. The result is compared with Kuhn-Santamaria model, Isgur-Morningstar-Reader model and Feindt model. Good consistency between data and the three models is shown within the experimental error range. The comparison with the structure function of τ→3π^±v measured by OPAL Collaboration also shows there is no obvious difference within 0.52.     

Partial wave analysis ofJ/ψ）→ppπ0 and measurement of J/ψ→ppη,ppη＇

Based on 58 million J/ψ data collected with the BESII detector at the BEPC, Partial Wave Analysis（PWA） is performed on J/ψ→ppπ0. The new excited baryon N（2065） is confirmed. Clear signals for other N＊ states are observed and the corresponding masses, widths and spin-parity are also measured. Processes such as J/ψ→ppη,ppη＇
are also studied and the branching ratios are measured.     

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.     

由ψ(2S)→π+π－J/ψ道测量J/ψ轻子道衰变分支比

利用北京谱仪(BES)上取得的ψ(2S)数据,对ψ(2S)→π⁺π^－J/ψ,J/ψ→1⁺1^－和J/ψ→任意末态两个过程进行了细致的研究,得到J/ψ的轻子道衰变分支比为B(J/ψ→e⁺e^－)=(5.90±0.07±0.16)%和B(J/ψ→μ⁺μ^－)=(5.96±0.08±0.16)%,由此给出Be/Bμ的值为0.990±0.018±0.024.假定Be=Bμ,J/ψ的轻子道衰变分支比为B(J/ψ→1⁺1^－)=(5.93±0.05±0.16)%.上述结果可用来估计强相互作用耦合常数αs和QCD减除参数∧.     

π+-16O弹性散射的微观计算

本文用π核散射的微观描述,计算了T_π^lab=240、343MeV时π⁺-¹⁶O弹性散射微分截面,定性地符合实验。     

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.     

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。     

J/ψ→π03(π+π－)分支比的测定

用BESⅠ的7.8×10⁶J/ψ数据更为精确地测定了J/ψ→π⁰3(π⁺π^－)和J/ψ→ω²(π⁺π^－)的分支比(Br(J/ψ→π⁰3(π⁺π^－))=(2.52±0.06±0.43)%,Br(J/ψ→π⁰3(π⁺π^－))=(1.31±0.09±0.21)%.同时对4π不变质量谱和ωππ不变质量谱进行研究分析,试图观察是否存在有兴趣的信号.     

在J/ψ衰变与ρ→π+π–π0衰变中的ρ–ω干涉

通过分析J/ψ→π⁺π^-π^{0π0来研究ρω干涉.利用描述J/ψ衰变的一般的唯象模型对PDG-2002关于J/ψ衰变到PP和PV的实验数据做了拟合(P表示赝标介子,V表示矢量介子) ,得到ρ0→π+π-π0反常大的分支比～10-3—10-2.理论的分析结果也与这一反常大的分支比相符合.同时,得到了合理的ηη′混合角和组分夸克质量比:θ=-19.68°±1.49°,m_u/m_s≈0.6 .}     

双例外原子（π土μ干）的四体衰变

本文利用复合粒子量子场论的微扰展开方法计算了双例外原子（π^&;#177;μ^?）的四体衰变的几率,并与自由μ衰变作了比较。     

π—18O非弹性散射的DWIA分析

我们在程函扭曲的DWIA框架下,用跃迁密度方法计算了180MeV和230MeV的π在¹⁸O上的非弹性散射到2⁺（1.98MeV）激发态的微分截面,分析了π^-对π⁺的截面比,研究了中子分布半径对微分截面的影响,我们的结果与实验定性符合。     

(π+,d)反应理论

本文在π介子的一核子吸收模型下,导出了（π⁺,d）反应的扭曲波玻恩近似的截面公式,在平面波近似下,对¹²C（π⁺,d）¹⁰C 反应作了估计.认为,这一类反应对于研究π吸收的过程和原子核的对结构都是值得重视的反应.     

16O+24Mg和20Ne+24Mg弹性散射的机制

本文考虑了两碰撞核间核子结团的转移机制, 解释了象¹⁶O+²⁴Mg和²⁰Ne+²⁴Mg这样一些4N核间的弹性散射微分截面后角振荡上升的反常现象. 在原子核分子轨道模型的理论框架下, 将交换势的强度作为唯一的可调参数, 数值计算较自然地拟合实验结果.