We analyze the rare and flavor changing decay of the top quark into a charm quark and a gauge boson in the littlest Higgs model with T-parity (LHT). We calculate the one-loop level contributions from the T-parity odd mirror quarks and gauge bosons. We find that the decay t → cV, (V = g, γ, Z) in the LHT model can be significantly enhanced relative to those in the Standard Model. Our numerical results show that the top quark FCNC decay can be as large as Br(t → cg) ∼ 10 −2 , Br(t → cZ) ∼ 10 −5 and Br(t → cγ) ∼ 10 −7 in the favorite parameter space in the LHT model.
PACS: 14.65.Ha,12.60.-i,12.15.Mm 12 s d 13 e −iδ d 13 −s d 12 c d 23 e iδ d 12 − c d 12 s d 23 s d 13 e i(δ d 13 −δ d 23 ) c d 12 c d 23 − s d 12 s d 23 s d 13 e i(δ d 13 −δ d 12 −δ d 23 ) s d 23 c d 13 e −iδ d 23 s d 12 s d 23 e i(δ d 12 +δ d 23 ) − c d 12 c d 23 s d 13 e iδ d 13 −c d 12 s d 23 e iδ d 23 − s d 12 c d 23 s d 13 e i(δ d 13 −δ d 12 ) c d 23 c d 13 .(2.11)
Flavor changing effects on the processes t → cH, e + e − → bs, e + e − → bsH and pp → bs in the LHT model are investigated in this paper. We calculate the oneloop level contributions from the T-parity odd mirror quarks and gauge bosons. The results show that the top quark rare decay t → cH in the LHT model can be significantly enhanced relative to that in the SM. The bs production at linear colliders in the LHT model can enhance the SM cross section a lot and reach 0.1 fb in some parameter space allowed in the experiment. But the heavy gauge boson and mirror fermion loops have small contribution to the processes pp → bs and e + e − → bsH. So the LHT effect on e + e − → bs might be detected at future linear colliders, while it's too small to be seen for the e + e − → bsH and pp → bs processes at future linear colliders and LHC.
For very large values of tan, the charged Higgs boson pair production via b b annihilation can proceed dominantly at the large hadron collider (LHC). We calculated the cross sections of the charged Higgs boson pair production via subprocess b b ! H H ÿ at the LHC including the next-to-leading order (NLO) QCD corrections in the minimal supersymmetric standard model (MSSM). We find that the NLO QCD corrections can significantly reduce the dependence of the cross sections on the renormalization and factorization scales.
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