New physics contributions to moments of inclusive $b\to c$ semileptonic decays

Abstract

Inclusive semileptonic $B\to X_c\ell {\bar{\nu }}_{\ell }$ decays, where $\ell =\mu ,e$, are by now standard candles in the determination of the CKM element $|V_{cb}|$. These determinations rely on the heavy-quark expansion and use moments of decay spectra to extract the non-perturbative parameters directly from data under the standard model assumption. At the same time, new physics could influence the moments of the inclusive decay. In this paper, we compute power-corrections and next-to-leading order corrections in the strong coupling constant using the full basis of dimension-six new physics operators for the inclusive $B\to X_c\ell \bar{\nu }$ decay. We provide predictions for lepton energy, hadronic and leptonic invariant mass moments, and perform a phenomenological study to show the possible impact of new physics. Our results could be used to perform a global fit including new physics contributions.

Comments: 28 pages, 7 figures. v2: version published in JHEP; added Appendix B