Alleviating the $\bar B \to D \tau \nu$ and $\bar B \to D^* \tau \nu_\tau$ puzzle in the MSSM

Abstract

We show that Supersymmetric effects driven by penguin contributions to the $b \to c \tau \nu_\tau$ transition are able to account simultaneously for a sizeable increase of both branching ratios of $\bar{B}\to D \tau\bar{\nu}_{\tau}$ and $\bar{B} \to D^{*} \tau\bar{\nu}_{\tau}$ with respect to the Standard Model predictions, thereby approaching their experimentally measured values. We emphasise that a light chargino and neutralino, with masses less than 300 GeV, in addition to a large stau/snueutrino mass and a large $\tan\beta$, are essential for enhancing the effect of the lepton penguin $\tau \nu_\tau W^{\pm}$, which is responsible for the improved theoretical predictions with respect to current data.