General analysis of (B)over-bar → (K)over-bar(*)l+ l- decays at low recoil

We analyze the angular distributions of (B) over bar -> (K) over bar* (-> (K) over bar pi)l(+) l(-) and (B) over bar -> (K) over barl(+) l(-) decays in the region of low hadronic recoil in a model- independent way by taking into account the complete set of dimension- six operators [(s) over bar Gamma b][(l) over bar Gamma'l]. We obtain several novel low- recoil observables with high sensitivity to nonstandard-model Dirac structures, including CP asymmetries, which do not require flavor tagging. The transversity observables H-T((1,3,4,5)) are found to be insensitive to hadronic matrix elements and their uncertainties even when considering the complete set of operators. In the most general scenario we show that the low recoil operator product expansion can be probed at the few-percent level using the angular observable J(7). Higher sensitivities are possible assuming no tensor contributions, specifically by testing the low-recoil relation vertical bar H-T((1))vertical bar = 1. We explicitly demonstrate the gain in reach of the low-recoil observables in accessing the ratio vertical bar C-9/C-10 vertical bar compared to the forward-backward asymmetry, and probing CP-violating right-handed currents ImC(10'). We give updated Standard Model predictions for key observables in (B) over bar -> (K) over bar (()*())l(+) l(-) decays. DOI: 10.1103/PhysRevD.87.034016