New Physics in inclusive semileptonic $B$ decays

Abstract

We study inclusive semileptonic $\bar{B}\to X_c\ell \bar{\nu }$ decays ($\ell =e,\mu$) in the presence of generic physics Beyond the Standard Model (BSM) that is heavy compared to the $b$-quark mass. Its effect is encoded in the Wilson coefficients of dimension-six operators of the Weak Effective Theory (WET). We compute the resulting BSM contributions to the experimentally measured kinematic moments and the total decay rate through order $\mathcal{O}({\Lambda }_{\mathrm{QCD}}^3/m_b^3)$ in the Heavy Quark Expansion, as well as the $\mathcal{O}({\alpha }_s)$ corrections for the right-handed vector current. We then perform fits to the full set of available inclusive measurements in several single-mediator scenarios and in the full WET basis. We find qualitatively new bounds in several of these scenarios, complementary to and competitive with constraints from exclusive decays.

Comments: 30 pages, 11 figures, 11 tables. Comments welcome. v2: references updated, footnote 8 added