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.     

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.     

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.     

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.     

Measurement of Inclusive Semileptonic Branching Fractions for D－→e－X and D0→e－X

We report a measurement of the absolutely inclusive semileptonic branching fractions of D^－ and D⁰ mesons, using a data sample of 22.3pb^－1 collected with BES detector at BEPC e⁺e^－ Collider at s=4.03GeV and based on the method of "combinative D⁺ and D⁰ single and double tags". The measured values of the branching fractions for D^－→e^－X and D⁰→e^－X are (21.8±8.5±4.2)% and (8.9±3.0±1,6)%, respectively. The measured ratio of the branching fractions is BF(D^－→e^－X)/BF(D⁰→e^－X)=2.4±1.7±0.8.     

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.     

A Rigorous Calculation for the Radiator in e+e－ Process

Using the precise expression of electron,positron distribution function we obtained earlier,we derive the rigorous analytical expression of radiator in e⁺e^－ collision process.This series expression converges rapidly to the precise result required.The comparison with existing approximate expression is also given.Our result benefits the precice calculation for the radiative corrections in e⁺e^－ collision processess.     

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.     

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.     

One Loop Effects to the Process e+e－→bs in Topcolor-Assisted Multiscale Technicolor Model

We calculated the Pseudo-Goldstone bosons (technipions, top-pious) corrections to the cross-section a of the process e⁺e^－→bs in topcolor-assisted multiscale technicolor model at LEP Ⅱ energy region. Our results show that, with reasonable value of the parameters, the cross-section is one order larger than that predicted by the standard model. We discussed the possibility of detecting this rare event at the B-factoly.     

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.     

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.     

Radiative Corrections to the Zbb and Zτ+τ－ Vertices in a Realistic One-Family Extended Technicolor Model

In a realistic effective one-family extended technicolor(ETC)model without exact custodial symmetry, we calculate the one-loop corrections to the Zbb and Zτ⁺τ^－ vertices from the sideways and diagonal ETC gauge boson exchange.The results show that both the Z→ bb partial Width Γ_b and branching ratio R_b and the τ polarization asymmetry parameter A_τ are enhanced by the corrections and are in agreement with the present experimental data.     

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.     

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.     

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.     

Measurement of Production Cross Section of Ds+Ds－ in e+e－ Annihilation at the Center-of-Mass Energy of s=4.03GeV

Measurement of the production cross section of the D+s D- s in e+e- annihilation at the Center-of-Mass Energy of s=4.03 GeV is reported in the paper. The cross section for the D+s D- s production has been measured using a data sample of 22.3 pb^－1 collected with BES detector at BEPC e+e- collider. The D+ s measons are reconstructed in the π+,K*0 K+ and K0K+ decay modes. A total number of 94±13 singly tagged D+ s events is obtained from the three modes. This yelds the cross section value σ prod D+s D－ s=(451±63±118)pb for D+ s D－ s production. Based on the numbers of singly tagged D+ s events for each of the three decay modes,the decay branching fractions for D+ s→K *0 K+ and K0K+ have been determined to be (3.02±0.94±0.91)% and (3.28±1.22±0.94)%,respectively.     

Influence of Interference Terms on Probability of Color Connections among Partons in e+e－→qq+ng Process

Large N_c approximation is adopted in popular e⁺e^－ event generators where the production probability of singlet chain states is 100% and that of color separate states is 0. In the real world N_c=3, we investigate the origin and character of color and kinematics aspects in interference terms. We find that the production probability of color singlet chain states decreases from 83%, 77% to 67%, 58% for qq+2g and qq+3g system respectively after considering the interference terms. Especially, the production probability of color separate states increases to twice of that without interference terms for qq+2g. Hence when n is larger, we can expect that the production probability of singlet chain states will be far less than 1 and that of color separate states will significantly increase when n is larger.