B -> Xs\gamma constraints on the top quark anomalous t-> c\gamma coupling

TL;DR

This paper derives constraints on the anomalous top quark decay t->cγ using B->Xsγ decay measurements, providing bounds that are comparable to current collider sensitivities and informing new physics searches.

Contribution

It introduces a method to constrain the t->cγ coupling via B meson decay data, linking flavor physics to top quark anomalous couplings.

Findings

Constraints on t->cγ branching ratio are about 6.5-8.5 x 10^{-5}

Bounds are comparable to ATLAS and CMS discovery potentials

Provides a novel indirect probe of top flavor-changing neutral currents

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 $\kappa_{\rm{tcR}}^\gamma$, the constraints correspond to the upper bounds $\mathcal B (t \to c + \gamma)<6.54 \times 10^{-5}$ (for $\kappa_{\rm{tcR}}^\gamma>0$) and $\mathcal B (t \to c + \gamma)<8.52 \times 10^{-5}$ (for $\kappa_{\rm{tcR}}^\gamma<0$), 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 $10 \ \rm{fb}^{-1}$ integrated luminosity operating at $\sqrt{s} =14$ TeV.