Simultaneous explanation of the R K and R D * $$ {R}_{D^{\left(*\right)}} $$ puzzles: a model analysis

Abstract

R K and R D ( * ) are two B-decay measurements that presently exhibit discrepancies with the SM. Recently, using an effective field theory approach, it was demonstrated that a new-physics model can simultaneously explain both the R K and R D ( * ) puzzles. There are two UV completions that can give rise to the effective Lagrangian: (i) V B: a vector boson that transforms as an SU(2) L triplet, as in the SM, (ii) U 1 : an SU(2) L -singlet vector leptoquark. In this paper, we examine these models individually. A key point is that V B contributes to B 0 s -B 0 s mixing and τ → 3µ, while U 1 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(τ − → µ − µ + µ − ) 2.1 × 10 −8 . This is measurable at Belle II and LHCb, and therefore constitutes a smoking-gun signal of V B. For U 1 , there are several observables that may point to this model. Perhaps the most interesting is the lepton-flavor-violating decay Υ(3S) → µτ , which has previously been overlooked in the literature. U 1 predicts B(Υ(3S) → µτ )| max = 8.0 × 10 −7 . Thus, if a large value of B(Υ(3S) → µτ ) is observedand this should be measurable at Belle II -the U 1 model would be indicated.

Probing lepton-flavour universality with $$K\rightarrow \pi \nu \bar{\nu }$$ K → π ν ν ¯ decays

“…In particular, attempts to provide a combined/coherent explanation for both charged-and neutralcurrent anomalies have been presented in Refs. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. One of the puzzling aspects of the present anomalies is that they have been seen only in semileptonic B decays and are quite large compared to the corresponding SM amplitudes.…”

New physics in b→sμ+μ− after the measurement of Alok1, Bhattacharya2, Datta3 et al. 2017Phys. Rev. DSelf Cite16541970View full textAdd to dashboardCite

“…(This said, this conclusion can be evaded if the LQs couple to other leptons, see Ref. [71] for an example. )…”

“…In Ref. [71], it was argued that one has to use model-independent results carefully, because they may not apply to all models. To be specific, a particular model may have additional theoretical or experimental constraints.…”

Lepton-flavor universality limits in warped space

“…The corrections to the R D ( * ) observables from the effective operators are given, in terms of the Wilson coefficients, as [12] …”