Alleviating the $\bar{B}\to D\tau \nu$ and $\bar{B}\to D^{\ast }\tau {\nu }_{\tau }$ 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 $\bar{B}\to D^{\ast }\tau {\bar{\nu }}_{\tau }$ 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.

Comments: 14 pages, 8 figures