Feasibility study of CP violation in decays at the Super Tau Charm Facility
Haoyu Sang (University of Science and Technology of China, Hefei 230026, China, State Key Laboratory of Particle Detection and Electronics, Hefei 230026, China); Xiaodong Shi (University of Science and Technology of China, Hefei 230026, China, State Key Laboratory of Particle Detection and Electronics, Hefei 230026, China); Xiaorong Zhou (University of Science and Technology of China, Hefei 230026, China, State Key Laboratory of Particle Detection and Electronics, Hefei 230026, China); Xianwei Kang (Beijing Radiation Center, Beijing 100875, China, Key Laboratory of Beam Technology of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875, China); Jianbei Liu (University of Science and Technology of China, Hefei 230026, China, State Key Laboratory of Particle Detection and Electronics, Hefei 230026, China)
We report a feasibility study for violation in $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ decays at a Super Tau Charm Facility (STCF). With an expected luminosity of 1 ab $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ collected by STCF per year at a center-of-mass energy of 4.26 GeV, the statistical sensitivity for CP violation is determined to be of order $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ by measuring the decay-rate difference between $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ and $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ . The analysis is performed using a reliable fast simulation software package, which can describe the detector responses properly and vary the responses flexibly for further optimization. Moreover, the energy-dependent efficiencies for reconstructing $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ are presented. The expected CP sensitivity is proportional to $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ in the energy region from 4.0 to 5.0 GeV. The sensitivity of CP violation is of order $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ with 10 ab $\tau^{-}\rightarrow K_{S}\pi^{-} \nu_{\tau}$ integrated luminosity, which is equivalent to ten years' data taking in this energy region at STCF.
