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.     

高能e++e－→e++e－+强子过程中的电弱干涉效应

在这篇文章中, 我们用[2]中的结果讨论了与极化光子结构函数相关的电弱干涉效应, 这个效应提供了对G-W-S(格拉肖-温伯格-萨拉姆)模型作进一步检验的可能并且导致对光子结构函数的更深入的了解.     

ELECTROWEAK INTERFERENCE EFFECTS IN THE HIGH ENERGY e++e－→e++e－+ HADRONS PROCESSES

In this paper we examine the electroweak interference effects related to the polarized photon structure functions making use of the results of the ref.[2]. The effects provide the probability of a further test of the G-W-S model and may lead to a deep understanding to the photon structure functions.     

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.     

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.     

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.     

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。     

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.     

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.     

Nonfactorization in D+→K0K+ Decays

We analyze D⁺→K⁰K⁺decay at the leading order, α s corrections with the QCD factorization approach and the soft-gluon effects with the light cone QCD sum rules. We find the prediction of naive factorization is far from the experimental data, and the QCD factorization result approaches to the experimental data. However, in QCD factorization method, if we consider the soft-gluon effects, then the result is in accordance with the experimental data well. Our calculation shows that the soft-gluon contributions which are firstly calculated in D meson nonleptonic decay are noticeable. So, it can't be neglected in the decay channel.     

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.     

Study of the e+ e－ to hadrons via ISR at BABAR

Experimental data from the PEP-II B-factory at 10.6 GeV center-of-mass （c.m.） energy, obtained via initial-state radiation （ISR） with the BABAR detector, are presented. The cross sections for many hadronic processes have been measured from the production threshold to 4-5 GeV of the e^＋e^- c.m. energy. The obtained data allow to study a number of intermediate states and determine the parameters of known resonances and their branching fractions. The exclusive cross section for some number of hadronic sub-processes are presented.     

高能e+e－→两喷注时的夸克产生律

本文利用e⁺e^－→重夸克jets中, 可分辨电磁激发与强作用产生的夸克的优点, 对后者的产生规律作了研究, 发现它产生的夸克对数满足一种简单普适规律, 由此算出的、i>多重数分布、前后关联等等都和实验符合、本文介绍了与的比较.     

RAPIDITY DISTRIBUTION AND BARYON-ANTIBARYON CORRELATIONS IN e+e－→TWO JET EVENTS

We extend our model by introducing explicitly the energy-momentum of quarks.By using the Monte-Carlo method,the rapidity distribution in light jet events is calculated.Agreement with experiment data is good.The baryon-antibaryon correlations in rapidity,open angle,azimuthal angle are also given,which are in agreement with experiment on the whole.     

The Structures of Colour String for e+e－→qqg and γ→3g

In Lund model,the explanation of e⁺e^－→qqg→3 jets and γ→3g→h's is based on applying Lund string fragmentation model to their assumed structures of colour string for qqg and 3g systems.In this paper,starting from the colour wave functions of qqg and 3g systems,we study these colour string structures by QCD directly.The results reveal the reasonableness and accuracy of Lund string pictures.     

e+e－湮灭中的夸克组合律

本文指出, 夸克组合中快度近关联与QCD的要求一致, 并与慢强子先产生原则一起, 完全确定夸克组合律, 并自动排除重子偶素的产生. 给出了N对夸克随机组成介子、重子与反重子的计算公式. 把它用于e⁺e^－湮灭, 根本不需另引入双夸克对的真空激发等假定, 即自然解释了重子的显著产生.     

THE FRAGMENTATION SCHEMES IN e+e－ ANNIHILATION

The comparison of two fragmentation schemes used in the analysis of e⁺e^－ annihilation are presented in this paper.It is found that the independent fragmentation assumption is strongly disfavored by the data of the final particle multiplicities,and the string fragmentation assumption agrees with experiments.     

QCD JET IN POLARIZED e+e－ ANNIHILATION

Following perturbative QCD theory, the two-jet and three-jet angular distributions in polarized e⁺e^－ annihilation is computed using the dimensional regularization scheme. The azimuthal inhomogeneity caused by the polarization is discussed. We also compute the exact formulae of dependence on ε´,δ to the second order and discuss the correction to G.Sterman and S.Weinberg's result.     

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.     

e+e－湮没过程的多重数分布

本文分析了e⁺e^－ 湮没中多重数的实验分布, 指出可能是夸克数目服从四动量守恒限制下的Poisson分布, 加上组合过程影响的结果. 并利用一种在其他方面取得明显成功的夸克组合律作了计算, 得到与实验符合的结果. 还对轻夸克jet作了单独讨论.