Light-cone sum rules for S-wave B ? Kp form factors

We derive a set of light-cone sum rules relating the S-wave B -Kp hadronic form factors to the B-meson light-cone distribution amplitudes (LCDAs), taking into account the complete set of LCDAs up to and including twist four. These results complement the sum rules for the P-wave B?Kp form factors obtained earlier. We then use the new sum rules to estimate the S-wave contributions to B?Kpll decays as a function of the Kp invariant mass. We pay particular attention to the fact that the S-wave Kp spectrum cannot be modelled by a sum of Breit-Wigner resonances, and employ a more consistent dispersive coupled-channel approach. We compare our predictions for branching ratios and angular observables with LHCb measurements in two different kinematic regions, around K-*(892) and K-0(*)(1430). We observe an overall compatibility and discuss possible improvements of our model to obtain a better description of the B?Kp form factors over a large kinematic range.