北京谱仪III实验中寻找J/Psi带电轻子味破缺的辐射衰变过程

A study of J/Psi radioactive decay with charged lepton flavor violation (CFLV) in BESIII experiment, via J/Psi->gamma e mu/gamma mu tau/gamma e tau, in which taus undergo leptonic decay, producing visible final states with a photon plus one electron(positron) and one anti-muon(muon), is discussed in this proposal. This measurement will complete the search of CLFV research in charmonium decay in some.sense and can be used in testifying the BSM theories like those contain CLFV Yukawa couplings. The research plan of this analysis was discussed in detail in this proposal, including event selection, background estimation and interpretation. Study on simulation estimate the branch ratio can be measured with precision down to the order of 10^-7 with 1300 million J/Psi data accumulated in BESIII . A better precision of this measurement, expect to be of the order 10^-8, will be accomplished in the future，considering the goal of BESIII J/Psi data taking, which is 10 billion, and better performance on ETOF and inner tracker after upgrade. This research has the potential to be a remarkable.achievement in the world.

该项目拟在BESIII实验中，研究J/Psi带电轻子味破缺(CLFV)的辐射衰变。我们通过寻找J/Psi->gamma e mu/gamma mu tau来进行这样的研究，其中tau发生轻衰变。可探测到的末态中含有一个光子和两根带点径迹，分别被鉴别为电子( 正电子)和反muon(muon)。该课题可以完善在粲偶素中对带电轻子味破缺过程的研究， 并且可以检验诸如含有CLFV汤川耦合的模型，对新物理的参数提出约束。该报告中仔细讨论了对该课题的研究计划，包括事例选择，本底估计和最终结果的解释等。初步模拟的计算的结果表明，利用在BESIII积累的13亿J/Psi数据，对分支比测量精度可望达到10^-7数量级。BESIII上最终将取得100亿J/Psi数据，并在改善了ETOF和内部径迹探测性能之后，有理由相信测量精度可望进一步提高至10^-8量级。该项研究有望得到具有世界影响力的结果。

中微子振荡的现象揭示了轻子味量子数不是严格的守恒量。而对带电轻子味破缺(cLFV)过程的任何观测证据都将意味着对标准模型的突破。而至今没有任何证据确认带电轻子味破缺过程的存在。该项目通过J/ψ的辐射衰变过程：J/ψ→e/ µ来寻找cLFV过程。经过对BESIII实验于2009年到2012年积累的13亿J/ψ数据样本的分析，对J/ψ→e和J/ψ→µ的分支比上限分别达到1.6×10-7和1.4×10-7。在进一步提高对本底排除率，以及对BESIII积累的更大统计量的J/ψ样本（约一百亿J/ψ事例）进行处理后，这些结果将被发表。这将是在粲偶素衰变中最精确的cFLV过程的测量。