Anomalous tqγ coupling effects in exclusive radiative B-meson decays

Abstract

The top-quark FCNC processes will be searched for at the CERN LHC, which are correlated with the B-meson decays. In this paper, we study the effects of top-quark anomalous interactions tqγ in the exclusive radiative B → K^∗γ and B → ργ decays. With the current experimental data of the branching ratios, the direct CP and the isospin asymmetries, bounds on the coupling κ^γ_tcR from B → K^∗γ and κ^γ_tcR from B → ργ decays are derived, respectively. The bound on |κ^γ_tcR| from is generally compatible with that from . However, the isospin asymmetry ∆(K^∗γ) further restrict the phase of κ^γ_tcR, and the combined bound results in the upper limit,   < 0.21%, which is lower than the CDF result. For real κ^γ_tcR, the upper bound on is about of the same order as the 5σ discovery potential of ATLAS with an integrated luminosity of10 fb⁻¹. For B → ργ decays, the NP contribution is enhanced by a large CKM factor |V_ud/V_td|, and the constraint on tuγ coupling is rather restrictive,   < 1.44× 10⁻⁵. With refined measurements to be available at the LHCb and the future super-B factories, we can get close correlations between B → Vγ and the rare t → qγ decays, which will be studied directly at the LHC ATLAS and CMS.