Speaker
Description
The heavy quark expansion (HQE) provides a well established framework to compute inclusive decay widths of heavy hadrons in terms of a systematic expansion in inverse powers of the constituent heavy quark mass. By including for the first time the contribution of the Darwin operator, SU(3)$_F$ breaking corrections to the matrix element of dimension-six four-quark operators and the so-called eye-contractions, we update the SM predictions, based on the HQE, of the total widths of the $B^+$, $B_d$, and $B_s$ mesons, as well as of the lifetime ratios $\tau(B^+)/\tau(B_d)$ and $\tau(B_s)/\tau(B_d)$. Overall we find very good agreement with the corresponding experimental determinations, however, the prediction of $\tau(B_s)/\tau(B_d)$ is particularly sensitive to the value of the Darwin parameter and of the size of SU(3)$_F$ breaking in the non-perturbative input, which are so far still poorly constrained, leading to some tension in specific scenarios.
