Complete Analysis on the Short Distance Contribution of $B_s\to \ell^+\ell^-\gamma$ in Standard Model

TL;DR

This paper evaluates the short distance contributions to the rare decay $B_s o \, ext{leptons}^+ \, ext{leptons}^- \, ext{gamma}$ in the Standard Model, highlighting the significant impact of four-quark operators on the branching ratio.

Contribution

It provides a comprehensive calculation of the short distance effects, especially from four-quark operators, which were previously underestimated in this decay process.

Findings

The branching ratio is nearly tripled due to the new contributions.

Predicted branching ratio is up to 1.7×10⁻⁸.

Results are testable at LHCb and B factories.

Abstract

Using the $B_s$ meson wave function extracted from non-leptonic $B_s$ decays, we evaluate the short distance contribution of rare decays $B_s\to \ell^+\ell^-\gamma(\ell=e,\mu)$ in the standard model, including all the possible diagrams. We focus on the contribution from four-quark operators which are not taken into account properly in previous researches. We found that the contribution is large, leading to the branching ratio of $B_s\to \ell^+\ell^-\gamma$ being nearly enhanced by a factor 3 and up to $1.7\times 10^{-8}$. The predictions for such processes can be tested in the LHC-b and B factories in near future.