Form factors for BK l+l- decay

The exclusive BV(P)l+l- and BV decays, with a vector (V=K*, , …) or pseudo scalar (P=K, , …) meson in the final state are important for the search for flavour-changing new physics. In this paper we study one of the exclusive rare decays of pseudo scalar B mesons: BKl+l- by using a relativistic constituent quark model, including infrared connement. We calculate the relevant form factors of the (BP) transitions in the full kinematical range of momentum transfer. The calculated form factors are used to evaluate differential decay rates and polarization observables. We present numerical results on these observables using the covariant quark model. This model can be viewed as an effective quantum field theory approach based on an interaction Lagrangian of hadrons interacting with their constituent quarks. Universal and reliable predictions for exclusive processes involving both mesons composed from a quark and antiquark and baryons composed from three quarks result from this approach.