北京谱仪-III 上粲重子Λ+c 半轻子衰变Λ+c→Λe+νe 和Λ+c→Λμ+νμ的蒙特卡罗研究

摘要

通过分析e+e-→Λ+cΛ-c,Λ+cΛ-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+cΛ-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 for Λ+c meson semileptonic decaysΛ+c →Λe+νe andΛ+c →Λμ+νμby analyzing the Monte Carlo events generated for e+e-→Λ+cΛ-c ,where theΛ+cΛ-c baryon 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+νe andΛ+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.