Phenomenological Study On The τ Lepton-flavor-violating Decay At The Super т-c Factory

The Standard Model （SM） of particle physics is a SU（3）C ×SU（2）L× U（1）Y gauge theory. It describes the strong, weak and electromagnetic interactions in our nature. And the unification of the electroweak interaction is completed at the scale of （?）（102） GeV. Over the past 50 years, many interaction forms predicted by the SM have been verified one by one. With the discovery of the Higgs Boson in 2012, the last vacancy on searching for the SM particles was filled in. Although the SM has achieved a great success, the discoveries of some new physics phenomena make people believe that the SM is just a low energy approximation of a fundamental theory at a higher energy scale. Therefore, many new physics theories were born in recent years. The T→μγ lepton-flavor-violating （LFV） decay exists in many new physics models beyond the SM. In the next few years, some experiments such as the Super B Factory and the Super T-c Factory, will be able to reach the LFV branching ratio region of T→μγ predicted by many new physics models. So the research on searching for T→μγ LFV decay has become increasingly important. In this paper, I investigate the possibility of searching the lepton-flavor-violating T→μγ rare decay at the Super T-c Factory.At （?）=3.7 GeV, the event number of LFV signal produced at the Super T-c Fac-tory is at least 8 order of magnitude smaller than that of the background. By comparing the kinematic distributions of the LFV signal and the SM background, we develop an optimized event selection criteria which can eliminate the leading background events and significantly reduce the subleading background events. By analyzing the signal sig-nificance, we may conclude that new 2σ upper limit of about 1.9×10^-9 on Br（T→μγ） can be obtained at the Super T-c Factory, which is beyond the capability of Super-B fac-tory in searching T lepton rare decay. Next, we calculate the T→μγ process in the framework of scalar leptoquark model. Using Passarino-Veltman one-loop reduction method, we obtain the analytical expression of Br（T→μγ）. Then a joint constraint on λ1λ2 and MLQ can be derived from the upper bound on Br（T→μγ）. With 1000 fb-1 data expected at the Super T-c Factory, we get λ1λ2<7.2×10-2 [MLQ 800 GeV) and MLQ>900 GeV （λ1λ2 9×10-2） at 95% confidence level （C.L.）. Finally, we also give the analytical result of Br（T→μγ） and relevant parameter constrains in a model-independent formalism.The main innovation in this thesis is:We provided a method of searching for the lepton-flavor-violating process in the Super T-c Factory. And we developed an optimized event selection criteria which can significantly suppress the SM background and remarkably enhance the sensi- tivity of the new physics searching. By analyzing the relation between the brach-ing raio of the rare LFV decay and the leptoquark model as well as the model-independent formalizm, we could obtain more stringent limits on the parameters.