The LHCb experiment observed B+ --> pi+ mu+ mu- decay with 1.0 fb^-1 data, which is the first measurement of a flavor changing neutral current b --> d l+ l- decay (l = e, mu). Based on QCD factorization, we give Standard Model predictions for the branching ratios, direct CP asymmetries, and isospin asymmetry for B --> pi l+ l- decays, in the kinematic region where the dilepton invariant mass is small. We find that the contribution from weak annihilation enhances the direct CP asymmetry for low l+ l- pair mass. Anticipating improved measurements, we assess the utility of B+ --> pi+ l+ l- observables, when combined with B0 --> pi- l+ nu and B+ --> K+ l+ l-, for determining CKM parameters in the future.
@article{arxiv.1403.7410,
title = {Rates and Asymmetries of B --> pi l+ l- Decays},
author = {Wei-Shu Hou and Masaya Kohda and Fanrong Xu},
journal= {arXiv preprint arXiv:1403.7410},
year = {2014}
}
Comments
13 pages, 9 figures; version accepted for publication in PRD; references added