B→Vγbeyond QCD factorization

Abstract

We calculate the main observables in ${B}_{u,d}\ensuremath{\rightarrow}(\ensuremath{\rho},\ensuremath{\omega},{K}^{*})\ensuremath{\gamma}$ and ${B}_{s}\ensuremath{\rightarrow}({\overline{K}}^{*},\ensuremath{\phi})\ensuremath{\gamma}$ decays, i.e. branching ratios and $CP$ and isospin asymmetries. We include QCD factorization results and also the dominant contributions beyond QCD factorization, namely, long-distance photon emission and soft-gluon emission from quark loops. All contributions beyond QCD factorization are estimated from light-cone sum rules. We devise, in particular, a method for calculating soft-gluon emission, building on earlier ideas developed for analogous contributions in nonleptonic decays. Our results are relevant for new-physics searches at the $B$ factories, CERN LHC and a future superflavor factory. Using current experimental data, we also extract $|{V}_{td}/{V}_{ts}|$ and the angle $\ensuremath{\gamma}$ of the unitarity triangle. We give detailed tables of theoretical uncertainties of the relevant quantities which facilitates future determinations of these Cabibbo-Kobayashi-Maskawa parameters from updated experimental results.