Towards a Global Analysis of the $b\to c\bar{u} q$ Puzzle

Abstract

We study the nonleptonic decays $\bar{B}_s^0 \to D_s^{(*)+} \pi^-$ and $\bar{B}^0 \to D^{(*)+} K^-$ within the Weak Effective Theory (WET) up to mass-dimension six. We revisit the calculation of the hadronic matrix elements within QCD Factorization including the full set of WET operators. We recalculate the two-particle contributions to the hard-scattering kernels at next-to-leading order in $\alpha_s$, confirming recent results in the literature. We also calculate the three-particle contributions at leading order in $\alpha_s$, clarifying the procedure, refining the SM results in the literature, and providing for the first time the complete set of contributions within the WET. We use these results to perform a global phenomenological study of the effective couplings, putting bounds on the size of the WET Wilson coefficients in four distinct fit models. The fits include constraints from the nonleptonic $B$-meson decay width, which we calculate at the leading order for the full set of WET operators for the first time. This study is the first one to account for simultaneous variation of up to six effective couplings. We identify two distinct modes in all fit models and discuss how future measurements can be used to distinguish between them.