Top Quark Pairs Generated R Yu Said The Damage Effects And The Charged Higgs Research

The standard model (SM) has been successful in describing the strong, weak and electromagnetic interaction phenomena at the energy scale up to 10² GeV. From the past thirty years , the accelerators such as the LEP at the CERN and the Tevatron in the Fermion Lab, have already tested the SM precisely. One of the great experimental achievements of the SM is the discovery of the top quark in 1995, but the Higgs boson, which is the particle predicted by the SM, has not been discovered yet utill now. Due to many difficulties such as hierarchy problem, the Standard Model is only considered to be an effective theory of some underlying theory in low energy. Therefore, it will be an important task to find new physics beyond the Standard Model in both theoretical and experimental studies. The most attractive extension of the SM is the Minimal Supersymmetric Standard Model(MSSM). The MSSM predicts five physical Higgs bosons: two CP-even neutral Higgs bosons h⁰, H⁰, a pseudoscalar Higgs boson A⁰ and a pair of charged Higgs boson H^±. From the phenomenological point of view, if a light neutral Higgs boson was found, it is still very hard to tell which model it belongs to, since the fundamental properties of such a particle (quantum number, couplings, branching ratios, etc.) are almost the same in some models, e.g. in the SM and in the 'decoupling regime' of the MSSM (i.e., when M_A⁰ > 200 GeV, M_A⁰～M_H⁰～M_H^± >> M_h⁰). While the discovery of the charged Higgs boson is an unambiguous signature of existing new physics beyond the SM.In the theory of supersymmetry there is a quantum number called R-Parity which plays an important role. In the R-Parity conserved MSSM, superpartners can only be produced in pairs and the lightest supersymmetric particle ( LSP ) is stable; while in the R-parity violating ( R_p ) MSSM, superpartner can be singly produced and the LSP can decay into normal particles. From theoretical point of view, the MSSM dose not require that the R-parity must be a conserved quantum number, thus R_p -MSSM is a more general supersymmetry(SUSY) theory.In the R-conserving MSSM, the charged Higgs boson pair can be produced in either e⁺e^- orγγcollision mode.γγcollision is achieved by using Compton backscattered photons in the scattering of intense laser photons on the initial polarized e⁺e^- beams. Normally, the cross section forγγ→H⁺H^- is larger than that of e⁺e^-→H⁺H^- due to the fact that the production rate in e⁺e^- collision mode is s-channel suppressed. We present the calculations of the full one-loop radiative corrections to the process e⁺e^-→γγ→H⁺H^- in the MSSM.In recent years people has a great deal of interests in R-parity violating super-symmetric models. Physicists believe that an accurate measurement of top quark pair production at the present and future colliders should be possible in finding physical effects beyond the SM. Any deviation of observable in the top quark pair production process from the SM prediction would give a hint of new physics. We study the R lepton number violating effects on both processes e⁺e^-→tt|- and e⁺e^-→γγ→tt|-at a LC.The main innovations in this thesis are listed below:·In this thesis, we calculated the full one-loop radiative corrections to the process e⁺e^-→γγ→H⁺H^- in the MSSM for the first time. We present the accurate results of this process. Our calculation will be helpful for the LC experiments to detect charged Higgs boson and look for physics beyond the Stand Model.·In this thesis, we calculated the R lepton number violating effects on both the processes e⁺e^-→tt|- and e⁺e^-→γγ→tt|- at a LC for the first time, the R lepton number violating effects can significantly change the cross section from their R-conserving MSSM expectations for these two processes. So we can use these results to find R signal or to provide more stringent constraints on the R parameters.·In the calculation of the full one-loop radiative corrections to the process e⁺e^-→γγ→H⁺H^- in the MSSM, we give the results at the SPS1a' point from the SPA project. As a standard result, it is convenient for other people to compare in both theory and experiment.