SIMULTANEOUS EXPLANATION OF THE R-K AND R-D (*) PUZZLES: A MODEL ANALYSIS

Abstract

RK and RD(*) are two B-decay measurements that presently exhibit discrepancies with the SM. Recently, using an eective eld theory approach, it was demonstrated that a new-physics model can simultaneously explain both the RK and RD() puzzles. There are two UV completions that can give rise to the eective Lagrangian: (i) V B: a vector boson that transforms as an SU(2)L triplet, as in the SM, (ii) U1: an SU(2)L-singlet vector leptoquark. In this paper, we examine these models individually. A key point is that V B contributes to B0 s -B 0 s mixing and ! 3, while U1 does not. We show that, when constraints from these processes are taken into account, the V B model is just barely viable. It predicts B( ! +) ' 2:1108. This is measurable at Belle II and LHCb, and therefore constitutes a smoking-gun signal of V B. For U1, there are several observables that may point to this model. Perhaps the most interesting is the lepton- avor-violating decay (3S) ! , which has previously been overlooked in the literature. U1 predicts B((3S) ! )jmax = 8:0 107. Thus, if a large value of B((3S) ! ) is observed | and this should be measurable at Belle II | the U1 model would be indicated. (c) The Authors.