Inclusive $\bar{B}\to X_s{\ell }^{+}{\ell }^{-}$ at the LHC: theory predictions and new-physics reach

Abstract

We present theoretical predictions for observables in inclusive $\bar{B}\to X_s{\ell }^{+}{\ell }^{-}$ suitable for measurements at hadron colliders through a sum-over-exclusive approach. At low $q^2$ we calculate the branching ratio and three angular observables. At high $q^2$ we provide the branching ratio and the ratio of the $\bar{B}\to X_s{\ell }^{+}{\ell }^{-}$ rate with respect to the inclusive $\bar{B}\to X_u\ell \bar{\nu }$ 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 $\bar{B}\to K^{(\ast )}{\mu }^{+}{\mu }^{-}$ 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-$q^2$ region. Finally, we present current model-independent bounds on new physics and emphasize the potential of complementary analyses of $\bar{B}\to X_s{\ell }^{+}{\ell }^{-}$ at Belle II and the LHC.

Comments: 24 pages, 5 figures, 2 tables. v2: Number in last line of table 2 corrected. Conclusion unchanged. Matches published version incl. erratum