Inclusive B Xₛ ^+^- at the LHC: theory predictions and new-physics reach

We present theoretical predictions for observables in inclusive B Xₛ ^+^- 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 B Xₛ ^+^- rate with respect to the inclusive B Xᵤ rate with the same phase-space cut. We compare our predictions to an extraction of the experimental rate through a sum-over-exclusive method using branching ratios of the exclusive B K^ (*) ^+^- modes measured at LHCb. 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 B Xₛ ^+^- at Belle II and the LHC.