Tension in the inclusive versus exclusive determinations of $|V_{cb}|$: a possible role of new physics

Abstract

We reconsider the possibility that the tension in the $|V_{cb}|$ determinations from inclusive and exclusive $B$ decay modes is due to a new physics effect. We modify the Standard Model effective Hamiltonian for semileptonic $b\to c$ transitions including a tensor operator with a lepton flavour dependent coupling ${ϵ}_T^{\ell }$, and investigate separately the muon and electron modes. The interference term between SM and NP, proportional to the lepton mass, has different impact in the inclusive and exclusive $B$ modes to muon. Moreover, even when the lepton mass is small as for the electron, the NP effect is different in inclusive and exclusive $B$ channels. For both $\mu$ and $e$ we find a region of ${ϵ}_T^{\mu ,e}$ where the constraints from $B^{-}\to D^{(\ast )0}{\ell }^{-}{\bar{\nu }}_{\ell }$ and $B\to X_c\ell {\bar{\nu }}_{\ell }$ are satisfied for the same $|V_{cb}|$.

Comments: RevTex, 6 pages, 7 figures. One reference added; matches published version