Phenomenological Study In Some New Physics Models At TeV Colliders Via Some Produce And Decay Processes

The standard model(SM) of elementary particle describing strong and electroweak interac-tions is a gauge theory. The SM has been extensively tested by the precise experimental dataduring the past40years, but the mechanism of electroweak symmetry breaking remains anopen question and the scalar sector sufers from the problems of triviality and unnaturalness,etc. Thus the SM can only be an efective field theory below some high energy scale and itshould be replaced by a profound and consistent new theory at higher energy. So people havedone many active researchs and put forward some new physics models.Among these new physics models, the littlest Higgs model with T-parity (LHT), the sim-plest little Higgs (SLH) model and the the top-color-assisted technicolor (TC2) model wereremained popular candidates for new physics beyond the SM. These models predict some newparticles, such as the new heavy gauge bosons, heavy fermions and heavy scalar particles inthe LHT model, the light pseudoscalar, denoted by η, in the SLH model, the three CP-oddPseudo-Goldstone Boson, so called top-pions (Ï€_t^±, Ï€_t⁰) and an CP-even scalar called top-higgs(h_t⁰) in the TC2model, which can be regarded as typical features of these three models.Basing on the running large hadron collider (LHC) and the planning international linearcollider (ILC), we analyse the conceivable efects of new particles in the TC2, LHT and SLHmodels to some processes, which include the following aspects:(1) In the LHT model we perform an extensive investigation of the top quark rare three-body decays t→cV V (V=γ, Z, g) and t→cffˉ(f=b, Ï„, μ, e) at one-loop level. Our resultsshow that the branching ratios of t→cgg and t→cbˉb could reach O(10^-3) in the favoriteparameter space, which implies that these decays may be detectable at the LHC or ILC, whilefor the other decays, their rates are too small to be observable at the present or future colliders.(2) In the LHT model we study the possibility of the ILC to probe the LFV productionprocesses e+e (γγ)→l_i(l|-)_j. Our results show that the rates of γγ→l_i(l|-)_jcan reach1fb inoptimal cases, could fall within the3σ observing sensitivity of the ILC, which implies that theseprocesses may be observed at the ILC.(3) In the SLH model we investigate some processes of the associated production of a lightpseudoscalar boson η with a pair of top quarks ILC, i.e., e⁺e^-→t(t|ˉ)η and γγ→t(t|ˉ)η. We find that the cross sections of these two processes could reach O(1) fb in the favorite parameter spacein the SLH model, which is consistent with the results of the cross section of ttˉh in the standardmodel and the cross section of ttˉh⁰in the minimal supersymmetric standard model. It shouldbe clear that hundreds to thousands of η per year can be produced at the ILC.(4) In TC2model we study the flavor changing neutral current interaction induced e⁺e^-(γγ)→tcˉh_t⁰and the other three produce processes e⁺e^-(γγ)→ZÏ€_<sup>+Ï€_t^-and γγ→π_t⁺Ï€_t^-involvedcharged top-pions at the ILC. We calculate the total cross section, give the distributions oftransverse momenta, pseudo-rapid and invariant mass, and also considering the subsequent de-cay of these process. Therefore, our studies can help us to search for charged top-pions andtop-higgs, furthermore, to test the TC2mode1.