B -> Xsγconstraints on the top quark anomalous t-> cγcoupling

Abstract

Observation of top quark flavor changing neutral process $t\to c+\gamma$ at the LHC would be the signal of physics beyond the Standard Model. If anomalous $t\to c\gamma$ coupling exists, it will affect the precisely measured $\mathcal{B}(\bar{B}\to X_s\gamma )$. In this paper, we study the effects of a dimension 5 anomalous $tc\gamma$ operator in $\bar{B}\to X_s\gamma$ decay to derive constraints on its possible strength. It is found that, for real anomalous $t\to c\gamma$ coupling ${\kappa }_{\mathrm{tcR}}^{\gamma }$, the constraints correspond to the upper bounds $\mathcal{B}(t\to c+\gamma )<6.54\times 10^{-5}$ (for ${\kappa }_{\mathrm{tcR}}^{\gamma }>0$) and $\mathcal{B}(t\to c+\gamma )<8.52\times 10^{-5}$ (for ${\kappa }_{\mathrm{tcR}}^{\gamma }<0$), respectively, which are about the same order as the $5\sigma$ discovery potential of ATLAS ($9.4\times 10^{-5}$) and slightly lower than that of CMS ($4.1\times 10^{-4}$) with $10{\mathrm{fb}}^{-1}$ integrated luminosity operating at $\sqrt{s}=14$ TeV.

15 pages, 5 figures. Revised. To appear in PRD

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