Search for new physics in B→D∗τnū[sub τ] decay

Abstract

B physics offers important tests of the Standard Model at low energies. Recently, BaBar observed significant deviations from the Standard Model expectations in the semileptonic B→D(*)τν¯τ decays. Interestingly, the measured leptonic B→τν branching fraction also deviates from CKM unitarity predictions. Motivated by these results we investigate the most general set of lowest dimensional effective operators leading to modifications of b→c(u) (semi)tauonic transitions. Allowing for general flavor violation, we find that among possible operator structures, new contributions from right-right vector and right-left scalar quark currents provide viable explanations of the anomalies. In addition, we identify a number of B→D*τν¯τ transition observables with the power to discriminate among the various effective operators' contributions. They are the differential decay rate, longitudinal D* polarization fraction, D*-τ opening angle asymmetry and the τ helicity asymmetry.