Global fit to b → cτν transitions

Abstract

We perform a general model-independent analysis of b→ cτν¯ transitions, including measurements of ℛ, ℛ, their q differential distributions, the recently measured longitudinal D* polarization FLD∗, and constraints from the B→ τν¯ lifetime, each of which has significant impact on the fit. A global fit to a general set of Wilson coefficients of an effective low-energy Hamiltonian is presented, the solutions of which are interpreted in terms of hypothetical new-physics mediators. From the obtained results we predict selected b→ cτν¯ observables, such as the baryonic transition Λ → Λ τν¯ , the ratio ℛ, the forward-backward asymmetries AFBD(∗), the τ polarization asymmetries PτD(∗), and the longitudinal D* polarization fraction FLD∗. The latter shows presently a slight tension with any new-physics model, such that an improved measurement could have an important impact. We also discuss the potential change due the very recently announced preliminary ℛ measurement by the Belle collaboration.