Global Analysis of Charmless $B$ Decays into Two Vector Mesons in Soft-Collinear Effective Theory

TL;DR

This paper uses soft-collinear effective theory to analyze charmless B to vector meson decays, fitting nonperturbative parameters with experimental data, and predicting various observables to compare with other theoretical approaches.

Contribution

It provides a comprehensive global analysis of B to VV decays within SCET, including charm penguins and polarization observables, with fitted parameters and predictions for future experiments.

Findings

Most results agree with current experimental data.

Charm penguins influence polarization and CP asymmetries.

Predictions can distinguish between theoretical approaches.

Abstract

Under the framework of soft-collinear effective theory, we analyze the charmless $B\to VV$ decays in a global way at leading power in $1/m_b$ and leading order in $\alpha_s$ with $V$ denoting a light vector meson. In the flavor SU(3) symmetry, decay amplitudes for the 28 decay modes are expressed in terms of 8 nonperturbative parameters. With 35 experimental results, we fit these 8 nonperturbative parameters. Annihilation contributions are neglected due to power suppression in the $m_b\to \infty$ limit, so we include in the fit the nonperturbative charm penguins, which will play an important role in understanding the direct CP asymmetries. Charming penguins are also responsible for the large transverse polarizations of penguin-dominated and color-suppressed decays. With the best fitted parameters, we calculate all possible physical observables of 28 decay modes, including branching fractions, direct CP asymmetries, and the complete set of polarization observables. Most of our results are compatible with the present experimental data when available, while the others can be examined on the ongoing LHCb experiment and the forthcoming Belle-II experiment. Moreover, the agreements and differences with results in QCD factorization and perturbative QCD approach are also discussed. A few observables are suggested to discriminate these different approaches.