The Study Of T~-â†'l~-P~0 Decays In Two New Physics Models

With the development of experimental and theoretical investigations, in addition to B physics and C physics ,τlepton physics is also focused by physicsts. The study ofτlepton physics could not only test the SM,but also explore the new physics. As one topic ofτlepton physics, Lepton flavor violation(LFV) could be a powerful tool to find and describ the new physics.Theτlepton is the only one massive enough to decay into hadrons. Its LFV decays (?)are good fields to study hadronic weak currents, flavor changing neutral current(FCNC), strong interaction , etc.Currently, Belle and Babar Collaboration have measured that, the branching ratios ofτLFV decays could reach to the order of (?). The Super-B factory under construction would explore theτLFV processesand provide more and more accurate data .Theoretically, the above-mentioned decays have been studied in different new physics models, such as Two-Higgs- Doublet Model of Type III(2HDM III), Flavour Changing Z ' Model, the SUSY Model, the Minimal Supersymmetric Standard Model(MSSM), R-Parity Violating Supersymmetry(RPV SUSY) Model,"Un- particle"Model, Type-III Seesaw Model and Top-color assisted with Technicolor Model. Their results show that these decay branching ratios could reach up to(?)This thesis studies the (?)decays in the 2HDM III and Flavour Changing Z ' Model, respectively. To deal with hadronic matrix element of the final state, we have used chiral perturbation theory approach. In the 2HDM III, these decays could occour at the tree level through the neutral Higgs H 0, h0,A0mediated. Our results suggest that, (?) have almost no significant effects on the values of(?)could not reach the experiment upper limit. While (?) could reach and even exceed the experimental data. With the current experimental constraints, we get the correlation of (?) and (?) Because tiny electron mass and (?)are too small to be observed. In the Flavour Changing Z ' Model, (?) decays could occur at the tree level through the neutral boson Z 'mediated. We use the latest experimental upper limit to constrain the parameters(?), and get the parameter spaces: (?). Our results provide a possible explanation for 2HDM III and Flavour Changing Z ' Model.