Testing leptoquark models in $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$

Abstract

We study potential New Physics effects in the $\bar{B}\to D^{(\ast )}\tau \bar{\nu }$ decays. As a particular example of New Physics models we consider the class of leptoquark models and put the constraints on the leptoquark couplings using the recently measured ratios $R(D^{(\ast )})=BR(\bar{B}\to D^{(\ast )}\tau \bar{\nu })/BR(\bar{B}\to D^{(\ast )}\mu \bar{\nu })$. For consistency, some of the constraints are compared with the ones coming from the current experimental bound on $BR(B\to X_s\nu \bar{\nu })$. In order to discriminate various New Physics scenarios, we examine the correlations between different observables that can be measured in future.

Comments: 29 pages, 7 figures, Note added: in the present version, we have modified $h_{T_3}(w)$ in Eq.(48b) although this had already been done in the published journal version.)