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 BES 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 BES Monte Carlo simulation package. In the BES 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.
We study the effects of the fourth quark generation model in ■_s →π-K+decay.Combining with the up-to-date experimental measurement for B(■_s →π-K +) and A dir cp(■_s →π-K +) by the CDF Collaboration,we derive the new bound of weak phase φ bd,which are 0 < φ bd < 44,321 < φ bd < 360 and 0 < φ bd < 26,342 < φ bd < 360 for m t = 400 and 600 GeV respectively.In these regions,B(■_s →π-K +) and A dir cp(■_s →π-K +) consist with the current experimental data within errors.
Based on the branching fractions of J/ψ→ VP from different experiments, we investigate the properties of the coupling constants of J/ψ→ VP decays using a model-dependent approach. We find that the octet coupling constant, g8 , of strong interaction is about twice larger than that of the singlet coupling constant g1 ; the electromag- netic breaking parameters g i E are larger than the mass breaking parameters giM , moreover, the three parameters of the electromagnetic effect are about equal, but the three parameters of the mass effect are obviously different and their uncertainties are also large; and the phase angle between strong and electromagnetic interactions is in the range of 70°-80°. It deepens our understanding of the coupling constant of J/ψ→ VP decays.
In this paper, we calculate the branching ratios of Λb→pK-and p∏- decays in the flavor changing Z' model. We find that the branching ratios for these two decay modes are sensitive to the contributions of the Z' boson. For Λb→pK decay, if the left-handed couplings are equal to the right-handed couplings, the branching ratio of this decay could match up to the currently experimental data for ξs =0.01 and -52° <φsL<132°, or ξs =0.004 and 0°<φsL<84; if only the left-handed couplings are considered, it could match up to the experimental data for ξs =0.01 and 10<φsL<138. And for Λb→p∏- decay, if the left-handed and right-handed couplings are equal, the branching ratio of Λb→p∏- decay may be consistent with the currently experimental data with ξd =0.05 and -135<φdL<43°, if only the left-handed couplings are considered, it may be consistent with ξd =0.05 and -114<φsL<8°.
The possibility of studying D 0-D 0 mixing at a giga-Z linear collider "Z factory" where 10 9 hadronic Z 0 decays can be accumulated is examined.We discuss the sensitivity for the measurements of neutral D mixing parameters.These results are compared to those attainable at B factories.We find that the typical decay length of the neutral D mesons at Z factory is about 10 times larger than that at B factory.In addition,the resolution of the vertex detector of a giga-Z factory is 2-3 times better than that of B factory.The proper time resolution at Z factory is about 20-30 times better than that at B factory.Therefore the determination of the mixing parameters at a giga-Z factory is more precise.
LI HaiBo 1 & YANG MaoZhi 2 1 Institute of High Energy Physics,P.O.Box 918,Beijing 100049,China
We have studied the associated production processes of a neutral top-Higgs in the topcolor assisted technicolor model with a pair of heavy quarks in γγ collisions at the International Linear Collider (ILC). We find that the cross section for ttht in γγ collisions is at the level of a few fb with the c.m. energy √s=1000 GeV, which is consistent with the results of the cross section of ttH in the standard model and the cross section of tth in the minimal supersymmetric standard model. It should be clear that hundreds of to thousands of ht per year can be produced at the ILC. This process of γγ→ttht is really interesting in testing the standard model and searching the signs of technicolor.
Abundant ψ' events have been collected at the Beijing Electron Positron Collider-Ⅱ (BEPCⅡ) that could undoubtedly provide us with a great opportunity to study the more attractive charmonium decays. As has been noticed before, in the process of J/ψ' decaying to the baryonic final states, pK-Λ, the evident Λ* and N* bands have been observed. Similarly, by using the product of χcJ from ψ' radiative decay, we may confirm this or find some extra new resonances. χc0's data samples will be more than χc1,2, taking into account the larger branching ratio of ψ' →γχc0. Here, we provide explicit partial wave analysis formulae for the very interesting channel ψ' →γχc0 →γpK-Λ.
In this paper,we calculate the production of a charged top pion in association with a W boson via gg fusion at CERN's Large Hadron Collider in the context of the topcolor assisted technicolor model.We find that the total cross section of pp→gg→W～(±)π_t～(■) is several dozen femtobarns with reasonable values of the parameters,and the total cross section of pp→W～(±)π_t～(■) can reach a few hundred femtobarns when we consider the sum of the contributions of these two parton subprocesses,gg→W～(±)π_t～(■) and b→W～(±)π_t～(■).
