Taming New Physics in $b\to c\bar{u}d(s)$ with $\tau (B^{+})/\tau (B_d)$ and $a_{sl}^d$

Abstract

Inspired by the recently observed tensions between the experimental data and the theoretical predictions, based on QCD factorisation, for several colour-allowed non-leptonic $B$-meson decays, we study the potential size of new physics (NP) effects in the decay channels $b\to c\bar{u}d(s)$. Starting from the most general effective Hamiltonian describing the $b\to c\bar{u}d(s)$ transitions, we compute NP contributions to the theoretical predictions of $B$-meson lifetime and of $B$-mixing observables. The well-known lifetime ratio $\tau (B^{+})/\tau (B_d)$ and the experimental bound on the semi-leptonic CP asymmetry $a_{sl}^d$, provide strong, complementary constraints on some of the NP Wilson coefficients.

Comments: 29 pages, 3 figures