Charmless ${\bar{B}}_s\to VV$ Decays in QCD Factorization

Abstract

The two body charmless decays of $B_s$ meson to light vector mesons are analyzed within the framework of QCD factorization. This approach implies that the nonfactorizable corrections to different helicity amplitudes are not the same. The effective parameters $a_i^h$ for helicity $h=0,+,-$ states receive different nonfactorizable contributions and hence are helicity dependent, contrary to naive factorization approach where $a_i^h$ are universal and polarization independent. The branching ratios for ${\bar{B}}_s\to VV$ decays are calculated and we find that branching ratios of some channels are of order $10^{-5}$, which are measurable at future experiments. The transverse to total decay rate ${\Gamma }_T/\Gamma$ is also evaluated and found to be very small for most decay modes, so, in charmless ${\bar{B}}_s\to VV$ decays, both light vector mesons tend to have zero helicity.

Comments: 16pages. Typos and mistakes fixed. Numerical results changed