Inclusive \( \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} \) at the LHC: theory predictions and new-physics reach

Abstract

We present theoretical predictions for observables in inclusive \( \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} \) suitable for measurements at hadron colliders through a sum-over-exclusive approach. At low q² we calculate the branching ratio and three angular observables. At high q² we provide the branching ratio and the ratio of the \( \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} \) rate with respect to the inclusive \( \overline{B}\to {X}_u\ell \overline{\nu} \) rate with the same phase-space cut. We compare our predictions to the B factory measurements and also to an extraction of the experimental rate through a sum-over-exclusive method using branching ratios of the exclusive \( \overline{B}\to {K}^{\left(\ast \right)}{\mu}^{+}{\mu}^{-} \) modes measured at LHCb. We find a consistent picture comparing Standard Model theory and experiment. As such, our analysis does not support a recent claim about a deficit in the inclusive branching ratio in the high-q² region. Finally, we present current model-independent bounds on new physics and emphasize the potential of complementary analyses of \( \overline{B}\to {X}_s{\ell}^{+}{\ell}^{-} \) at Belle II and the LHC.