Chargino Decay Under Study Supersymmetric Models

The Standard Model(SM) is a fundamental theory of particle physics and has made great success in recent decades. However, it also has some drawbacks. And the Minimal Supersymmetry Standard Model(MSSM), here the supersymmetry is a symmetry relating fermions with bosons, is the least expansion of the SM in the supersymmetry (SUSY) theory.In this article, we mainly study the decay of a supersymmetric particle, χ1, in the framework of the MSSM. In an R-parity conserved SUSY model, sparticles can only produced in pairs. The lightest supersymmetric particle (LSP), which in many scenarios is the lightest neutralino χ10. For a large number of decay chains, it always contain χ10in the final state. In experiments, it is difficult to produce much heavier supersymmetric particle. And we here study lighter supersymmetric particle χ1decaying into the lightest supersymmetric particle χ10.In this article we study the tree level decays at first, and we will give the approximate calculation in the case of Wμ-being on-shell. We conclude that the process of χ1â†'χ10+f+f’ can be converted to χ1â†'χ10+Wμ-and Wμâ†'f+f’. And we calculate the one loop corrections of Xi decay. In Quantum Field Theory(QFT), higher order corrections always contain ultraviolet(UV) divergence. In order to deal with this divergence, we should make renormalization for the fields and the free parameters.We may also confront the difficulty of infra-red(IR) divergences. We showed that IR divergences is canceled precisely through analytic calculation. We use phase-space-slice method to calculate soft photon and collinear photon corrections analytically, and calculate hard non-collinear photon corrections directly. In order to ensure the credibility of results, we verified that the rate is independent of the cut of Esoft and δηlγ.We find the mass and the width of χ1-in the choice of parameters in the range of M2=220-290GeV, Mμ=300GeV and M2=250GeV, Mμ=260-360GeV, respectively. And we calculate the width of Wμ-and branching ratio and compare the predictions with the SM ones. We also present the width of χ1in the case of Wμ-being on-shell, which help us to search for the signal of supersymmetry in the LHC experiments.