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。     

关于（e+e-）,（μ+μ-）原子在库仑场的裂解

本文应用了复合粒子场论的微扰展开理论和自旋为（1/2-1/2）的库仑相互作用原子的Bethe-Salpeter协变波函数的近似解,计算了（e⁺e^-）（μ⁺μ^-）原子的高速飞行下裂解截面及能谱。结果表明（e⁺e^-）原子的裂解截面比前人的计算约小20％。此外,计算还表明（e⁺e^-）及（μ⁺μ^-）原子的单态和三重态裂解截面对任意主量子数n,和极端相对论近似下将精确相等,而前人的计算中只是n=2时才有这一结果,而对n=1时,两者相差约有25％。看来很可能是计算中的错误所致。     

正负电子对撞中重轻子τ的弱电干涉产生和宇称破坏效应

我们建议测量过程 e⁺e^-→τ⁺τ^-→e⁺π^-（p^-,μ^-）+中微子中的级联π、ρ的能谱,以决定由于电磁和弱作用干涉引起的宇称破坏效应.在重窄共振处进行这种观察是特别合适的.从经验上我们猜测下一个这样的共振的质量大约是28—31 GeV/c².     

关于产生S态（π+π-）s 原子的直通图

本文求出了梯形近似下（π⁺π^-）_s 态原子的相对论协变的 B-S 波函数,并通过应用这一相对论协变的 B-S 波函数和假设复合场论微扰展开中的最低次项——“直通图”为主,计算了过程π⁺+n→p+（π⁺π^-）_s的截面,讨论了直通图的一些性质.此外,这一计算对如下更有兴趣的过程或许提供了粗略的估计:μ⁺+n→（μ⁺π^-）+p.     

Evidence for e+e-→γχc1,2 at center-of-mass energies from 4.009 to 4.360 GeV

Using data samples collected at center-of-mass energies of √s=4.009, 4.230, 4.260, and 4.360 GeV with the BES0 detector operating at the BEPC/ collider, we perform a search for the process e⁺e^-→γχ_c,j (J =0, 1, 2) and find evidence for e⁺e^-→γχ_c1 and e⁺e^-→γχ_c2 with statistical significances of 3.0σ and 3.4σ, respectively. The Born cross sections σ^B(e⁺e^-→γχ_c,j), as well as their upper limits at the 90% con dence level (C.L.) are determined at each center-of-mass energy.     

Event generators for η/η' rare decays into π+π-l+l- and e+e-μ+μ-

Study of the rare and forbidden decays of η/η' offers a sensitive probe to test fundamental symmetries of quantum chromodynamics and search for new physics beyond the Standard Model. To study the rare decays of η/η' to π⁺π^-e⁺e^-, π⁺π^-μ⁺μ^- and e⁺e^-μ⁺μ^- at the BESⅢ detector, we developed several event generators based on the vector meson dominant model with finite-width corrections and the pseudoscalar mesons mixing theory. The various distributions from event generators are in good agreement with the theoretical predictions, which indicates that the event generators work very well after implemention in the BESⅢ Monte Carlo simulation package. In the BESⅢ physics analysis, the performance of the event generators will be improved in accordance with the distributions of different variables of η/η' from data and the improvement on the theoretical calculations.     

光生相对论的（μ+μ-）,（e+e-）仲原子

本文应用复合场论微扰展开式和相对论的 B-S 近似波函数,计算了类似于 Primakoff 效应的光生相对论的（e⁺e^-）,（μ⁺μ^-）仲原子的过程.结果与通常点模型的计算结果不同,这里多得出了一个新的形状因子.这表明在通常的Primakoff 效应中也将存在类似的修正.     

自旋1/2的正反费米子电磁束缚态的近似的B-S波函数

本文在梯形近似下,求解了自旋1/2的正反费米子电磁束缚态的Bethe-Salpeter方程.除得到标准的满足 Balmer 系的本征值外,还得到了明显具有相对论协变性,具有正确解析性,满足谱条件的近似的 B-S 波函数.以η⁰→γ+（e⁺e^-）和η⁰→γ+（μ⁺μ^-）为例,表明上述所得到的近似波函数能方便地用来计算相对论电磁束缚态的产生、湮灭和跃迁等问题.     

在e+e-湮灭中轴子（Axion）的产生及其实验建议

我们计算了在e⁺e^-湮灭中轴子的产生截面,建议利用β⁺放射源在e⁺e^-湮灭实验中寻找轴子。我们还进一步讨论了在这种实验中所用探测器的性能要求。     

π+介子辐射衰变分枝比

本文应用标准微扰方法计算π介子衰变过程中π⁺→e⁺+v+r对π⁺→μ⁺+v的分枝比。文中应用了V-A型普适费米弱作用及沙拉姆提出的强作用,计算结果与目前实验结果没有矛盾。     

Analysis of Bs→φμ+μ- decay within supersymmetry

Motivated by the rst measurement on B(B_s→φμ⁺μ^-) by the CDF Collaboration, we study the supersymmetric e ects in semi-leptonic B_s→φμ⁺μ^- decay. In our evaluations, we analyze the dependences of the dimuon invariant mass spectrum and the forward-backward asymmetry on relevant supersymmetric couplings in the MSSM with and without R-parity. The analyses show that the new experimental upper limits of B(B_s→φμ⁺μ^-)from the LHCb Collaboration could further improve the bounds on sneutrino exchange couplings and (δ_LL^u)₂₃ as well as (δ_LL,RR^u)₂₃ mass insertion couplings. In addition, within the allowed ranges of relevant couplings under the constraints from B(B_s→φμ⁺μ^-), B(B→K^(*)μ⁺μ^-) and (B_s→φμ⁺μ^-), the dimuon forward-backward asymmetry and the di erential dimuon forward-backward asymmetry of B_s→φμ⁺μ^-are highly sensitive to the squark exchange contribution and the (δ_LL^u)₂₃ mass insertion contribution. The results obtained in this work will be very useful in searching for supersymmetric signals at the LHC.     

Determination of J/φ Event Number via J/φ→μ+μ- and J/φ→ e+e- at BESIII

The decays of J/φ→μ⁺μ^- and J/φ→ e⁺e^- are studied by Monte-Carlo simulation, based on the Beijing Spectrometer (BES)Ⅲ offline software system. The methods of determination of the J/φ event number via J/φ→μ⁺μ^- and J/φ→ e⁺e^- are presented, respectively. These methods can be used to determine the J/φevent number for the coming BESⅢ J/φ data sample.     

场流关系和π+→e++ν+γ的衰变过程

本文应用由复合场场论或场代数导出的轴矢流的场流恒等式计算了π介子的辐射衰变π⁺→e⁺+ν+γ过程。计算结果与目前的实验大致相合。     

原子核中的△（1236）对（p,π+）反应的影响

我们假定了一个p→Δ⁰+π⁺的一核子模型,在平面波玻恩近似下,把Δ⁰波函数取为谐振子形式,计算了²⁶Mg（p,π⁺）²⁷Mg 反应的微分截面.为了比较,在同样近似下,对 p→n+π⁺的一核子模型,也做了计算.结果表明,两种机制给出的角分布,无论大小和形状都有明显的差别.对于Δ⁰波函数,我们还选取了高动量成分较大的 Eckart 形式,由计算结果看出,它比谐振子波函数有很明显的改进.这表明,（p,π⁺）反应对束缚态波函数的高动量成分很敏感.     

Pure annihilation type decays B0→Ds- K2+ and Bs→Da2 in perturbative QCD approach

We calculate the branching ratios of pure annihilation type decays B⁰→D_s^- K₂^*+ and B_s→Da₂ using the perturbative QCD approach based on k_T factorization. The branching ratios are predicted to be (60.6_{-16.5-10.4-2.1}^{+17.3+4.3+3.2} )× 10^-6 for B⁰→D_s^- K₂^*+, (1.1_-0.4-0.2-0.1^+0.4+0.1+0.1)×10^-6 for B_s→D⁰a₂⁰ and (2.3_-0.8-0.4-0.1^+0.8+0.2+0.1)×10^-6 for B_s→D^-a₂⁺. They are large enough to be measured in the ongoing experiment. Due to the shortage of contributions from penguin operators, there are no direct CP asymmetries for these decays in the Standard Model. We also derive simple relations among these decay channels to reduce theoretical uncertainties for the experiments to test the accuracy of theory and search of new physics signal.     

Off-Shell Effect of Quarks in Bs→γe+e-

We evaluate the rare decays B_s→γe⁺e^- in the standard model, considering the off-shell effect of quarks in B_s meson as well as some contributions neglected in previous works. It is found that the quarks off-shell are large. With the predicted branching ratios at order of 10^-8, it is expected that the radiative dileptonic decays will be detected in the LHC-b experiments.     

Measurement of J/ψ decays into ΛΛ π+π-

Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π⁺π^- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π⁺π^-)=(4.30±0.13±0.99)×10^-3, excluding the decays to intermediate states, namely J/ψ→Ξ^-Ξ⁺, J/ψ→Σ(1385)^-Σ(1385)⁺, and J/ψ→Σ(1385)⁺Σ(1385)^-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ^-Ξ⁺)=（0.90±0.03±0.18）×10^-3, Br(J/ψ→Σ(1385)^-Σ(1385)⁺)=(1.23±0.07±0.30)×10^-3,and Br(J/ψ→Σ(1385)⁺Σ(1385)^-)=(1.50±0.08±0.38)×10^-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos²θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ^-Ξ⁺, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)^-Σ(1385)⁺, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)⁺Σ(1385)^-.     

Comprehensive analysis of e+e-→γηc(2S)

We discuss the production of η_c(2S) through the process e⁺e^-→γη_c(2S), where the leading contribution originates from 1-loop electroweak corrections. Adopting some reasonable light-cone distribution amplitudes, we analyze the cross section of this process. As the electron-positron center of mass energy √s=3770 MeV, the typical production cross section of this process is about 1 fb.     

弱电流不守恒情况下π-→π0+e+ν过程的几率

利用色散关系研究了弱电流不守恒情况下的π^-→π⁰+e+ν衰变过程。在对π—π散射相移作了一些假定后,证明了π、π中间态的贡献很小。在N、N中间态项中出现的N、N湮灭矩阵元用Chew-Ball理论及湮灭实验估计,同时出现的核子弱作用形状因子又用色散关系计算,证明了N、N中间态对它的贡献很小,计算了π、π中间态对它的贡献。根据现有N、N湮灭实验估计,π^-→π⁰+e+ν过程的衰变几率<6×10^-4秒^-1。     

相对论性电磁束缚系统（π±μ干）、（K±μ干）的库仑裂解与衰变

本文应用复合粒子量子场论的微扰展开式和相对论性的（π^&;#177;μ^?）、（K^&;#177;μ^?）的B.S.波函数,计算了在原子核屏蔽库仑场中高能（π^&;#177;μ^?）、（K^&;#177;μ^?）原子的裂解能谱和截面。在极端相对论近似下,对大多数原子核,它们的裂解截面分别约为10^-18cm²和10^-17cm²。利用同样的波函数,还计算了（π^&;#177;μ^?）→π⁰+v_μ（v_μ）,（K^&;#177;μ^?）→K⁰+v_μ（v_μ）,以及（π^&;#177;μ^?）→μ⁺+μ^-+v_μ（v_μ）,（K^&;#177;μ^?）→μ⁺+μ^-+v_μ（v_μ）的衰变几率。