Study of $B_s\to\ell^+\ell^-\gamma$ decays in covariant quark model

Understand

We study the rare radiative leptonic decays $B_s\to\ell^+\ell^-\gamma$ ($\ell=e,\mu,\tau$) within the Standard Model, considering both the structure-dependent amplitude and bremsstrahlung.

• In the framework of the covariant confined quark model developed by us, we calculate the form factors characterizing the $B_s\to\gamma$ transition in the full kinematical region of the dilepton momentum squared and discuss their behavior.
• We provide the analytic formula for the differential decay distribution and give predictions for the branching fractions in both cases: with and without long-distance contributions.
• Finally, we compare our results with those obtained in other approaches.