北京谱仪-Ⅲ上粲重子Λ_c^+半轻子衰变Λ_c^+→Λe^+ν_e和Λ_c^+→Λμ^+ν_μ的蒙特卡罗研究

Monte Carlo studies of the semileptonic decays for Λ_c^+→Λe^+ν_e and Λ_c^+→Λμ^+ν_μ at BES-Ⅲ

通过分析e+e-→Λ+c珚Λ-c,Λ+c珚Λ-c衰变到所有可能末态的蒙特卡罗样本模拟测量了粲重子Λ+c半轻子衰变过程Λ+c→Λe+νe和Λ+c→Λμ+νμ的绝对分支比。基于完整的蒙特卡罗模拟和物理分析,研究了BES-Ⅲ上测量Λ+c→Λe+νe和Λ+c→Λμ+νμ的这2个半轻子衰变分支比能够达到的精度。研究表明,如果在BES-Ⅲ上能够采集9(20)fb-1的e+e-→Λ+c珚Λ-c数据,Λ+c→Λe+νe和Λ+c→Λμ+νμ衰变分支比的测量精度能够达到4.5(3.2)%与5.7(4.0)%。该测量结果将对检验和刻度格点QCD理论和在更高的精度上检验标准模型理论提供至关重要的实验数据。

We simulate measurements of the absolute branching fractions forΛ＋cmeson semileptonic decaysΛ＋c→Λe＋νeandΛ＋c→Λμ＋νμby analyzing the Monte Carlo events generated for e＋e-→Λ＋c珚Λ-c,where theΛ＋c珚Λ-cbaryon pairs are set to automatically decay to all possible final states.These Monte Carlo events are simulated in the BES-III detector.Based on a full Monte Carlo simulation and full physics analysis,we study how well the absolute branching fractions forΛ＋c→Λe＋νeandΛ＋c→Λμ＋νμcan be measured with the data collected by the BES-III detector at the BEPC-II collider.It is found that we can measure these branching fractions at the accuracy levels of 4.5（3.2）% and 5.7（4.0）% with 9（20）fb-1 data.These measurements will be of great importance in more precisely calibrating the LQCD calculation and testing the standard model.