Lepton Flavor Violation inBDecays?

Abstract

The LHCb Collaboration's measurement of R K = B(B + → K + µ + µ − )/B(B + → K + e + e − ) lies 2.6σ below the Standard Model prediction. Several groups suggest this deficit to result from new lepton non-universal interactions of muons. But non-universal leptonic interactions imply lepton flavor violation in B-decays at rates much larger than are expected in the Standard Model. A simple model shows that these rates could lie just below current limits. An interesting consequence of our model, that B(75, is compatible with recent measurements of these rates. We stress the importance of searches for lepton flavor violations, especially for B → Kµe, Kµτ and B s → µe,

Diagnosing lepton-nonuniversality in b → sℓℓ

“…1 Previous measurements [3,4] had significantly larger uncertainties and were consistent with the SM prediction, which is R K = 1 to an excellent approximation [5]. Theory interpretations of the recent R K data are given in [6][7][8][9][10][11][12][13].…”

Dark matter relic from muon anomalies

“…We acknowledge, however, that explicit flavor completions of this model could lead to correlated effects in other mesonphysics and leptonic observables [19,[31][32][33][34][35][36].…”

Revisiting Lepton Flavour Universality in B Decays

“…Clearly, this picture might work only provided NP couples much more strongly to the third generation than to the first two. Such a requirement can be naturally accomplished in two ways: i) assuming that NP is coupled, in the interaction basis, only to the third generation of quarks and leptons -couplings to lighter generations are then generated by the misalignment between the mass and the interaction bases through small flavour mixing angles [14] -and ii) if NP couples to different fermion generations proportionally to their mass squared [15]. In the scenario i) LFU violation necessarily implies lepton flavour violating (LFV) phenomena.…”

“…[11][12][13][14][15][16][17]. The main new development of our study is the construction of the low-energy effective Lagrangian taking into account the running of the Wilson coefficients of a suitable operator basis and the matching conditions when mass thresholds are crossed.…”

“…Such a program has not been carried out in the literature so far and it has significant implications on the conclusions of Refs. [11][12][13][14][15][16][17]. The most important quantum effects turn out to be the modification of the leptonic couplings of the vector boson Z and the generation of a purely leptonic effective Lagrangian.…”