The flavor of a little Higgs with T-parity

Abstract

We analyze flavor constraints in the littlest Higgs model with T-parity. In particular, we focus on neutral meson mixing in the K, B, and D systems due to one loop contributions from T-parity odd fermions and gauge bosons. We calculate the short distance contributions to mixing for a general choice of T-odd fermion Yukawa couplings. We find that for a generic choice of textures, a TeV scale GIM suppression is necessary to avoid large contributions. If order one mixing angles are allowed in the extended flavor structure, the mass spectrum is severely constrained, and must be degenerate at the 1-5% level. However, there are still regions of parameter space where only a loose degeneracy is necessary to avoid constraints. We also consider the B s system, and identify a scenario in which the mixing can be significantly enhanced beyond the standard model prediction while still satisfying bounds on the other mixing observables. We present both analytical and numerical results as functions of the T-odd fermion mass eigenvalues.

Particle-antiparticle mixing,εK, ΔΓq, ASLq, ACP(Bd→ψKS), ACP(Bs→ψphi) and B→Xs,dγ in the Littlest Higgs model with T-parity

“…In the present paper we confirm the analytic expressions for the effective Hamiltonians for K 0 −K 0 , B 0 d −B 0 d and B 0 s −B 0 s mixings presented in [28] and we generalize the analysis of these authors to other quantities that allow a deeper insight into the flavour structure of the LHT model. However, before listing the new aspects of our paper relatively to [28], let us emphasize a few points about the model in question that have not been stated so far in the literature.…”

“…1 In the first phenomenological studies of the LHT model [27] the contributions of mirror fermions to physical observables have not been considered, while their impact on electroweak precision tests has been investigated in [24]. More recently, in an interesting paper by Hubisz et al [28] the role of mirror fermions in neutral meson mixing in the K, B and D systems has been studied in some detail. The main messages of [28] are:…”

“…More recently, in an interesting paper by Hubisz et al [28] the role of mirror fermions in neutral meson mixing in the K, B and D systems has been studied in some detail. The main messages of [28] are:…”

“…However, before listing the new aspects of our paper relatively to [28], let us emphasize a few points about the model in question that have not been stated so far in the literature.…”

“…• While the authors of [28] analyzed only the mass differences ∆M K , ∆M d , ∆M s , ∆M D and the CP violating parameter ε K , we include in our analysis also the CP asymmetries A CP (B d → ψK S ), A CP (B s → ψφ) and A q SL , and the width difference ∆Γ q , that are theoretically cleaner than the quantities considered in [28].…”