Phenomenology of inclusive $\bar{B}\to X_s \ell^+ \ell^-$ for the Belle II era

Abstract: With the first data being recorded at Belle II, we are at the brink of a new era in quark flavour physics. The many exciting new opportunities for Belle~II include a full angular analysis of inclusive ${\bar B \to X_{s} \, \ell<sup>+\ell<sup>-}$ which has the potential to reveal new physics, in particular by its interplay with the exclusive $b \to s \ell<sup>+\ell<sup>-$ counterparts studied extensively at LHCb. In this paper, we present fully updated Standard Model predictions for all angular observables necessary for this endeavour. These predictions are tailored to Belle II and include an elaborate study of the treatment of collinear photons which become crucial when aiming for the highest precision. In addition, we present a phenomenological study of the potential for Belle II to reveal possible new physics in the inclusive decay channel, both in an independent manner and in combination with exclusive modes.