Abstract
We consider the possibility that the neutral-current B anomalies are due to radiative corrections generated by Yukawa interactions of quarks and leptons with new vector-like quark and lepton electroweak doublets and new Standard Model singlet scalars. We show that the restricted interactions needed can result from an underlying Abelian family symmetry and that the same symmetry can give rise to an acceptable pattern of quark and charged lepton masses and mixings, providing a bridge between the non-universality observed in the B-sector and that of the fermion mass matrices. We construct two simple models, one with a single singlet scalar in which the flavour changing comes from quark and lepton mixing and one with an additional scalar in which the flavour changing can come from both fermion and scalar mixing. We show that for the case the new quarks are much heavier than the new leptons and scalars the B anomalies can be due to box diagrams with couplings in the perturbative regime consistent with the bounds coming from {B}_s-{overline{B}}_s , K-overline{K} and D-overline{D} mixing as well as other lepton family number violating processes. The new states can be dark matter candidates and, in the two scalar model with a light scalar of O(60) GeV and vector-like lepton of O(100) GeV, there can be a simultaneous explanation of the B-anomalies, the muon anomalous magnetic moment and the dark matter abundance.
Highlights
Recent measurements of B decays [1,2,3,4,5,6,7] have indicated there may be departures from the Standard Model (SM) predictions for processes induced by the neutral current quark-level transition b → sμ+μ−
We show that the restricted interactions needed can result from an underlying Abelian family symmetry and that the same symmetry can give rise to an acceptable pattern of quark and charged lepton masses and mixings, providing a bridge between the nonuniversality observed in the B-sector and that of the fermion mass matrices
In this paper we have explored the possibility that the neutral current anomalies observed in B decays come from loop effects generated by Yukawa couplings of SM fermions to new heavy SM singlet scalars and new heavy vector-like quark and lepton SM doublets
Summary
Recent measurements of B decays [1,2,3,4,5,6,7] have indicated there may be departures from the Standard Model (SM) predictions for processes induced by the neutral current quark-level transition b → sμ+μ−. Neutral current corrections involving loop effects of new scalars and fermions have already been explored in detail by Arnan, Hofer, Mescia and Crivellin [20] for a wide variety of SM representations for the scalars and quarks.2 Their overall conclusion is that to explain the b → sμ+μ− anomaly the couplings required are forced to be uncomfortably large in comparison with the bounds coming from Bs − Bs mixing unless the scalars carry SM quantum numbers and the heavy fermions are Majorana fermions. The appendices present two simple family symmetry variants capable of eliminating lepton flavour changing processes completely and allowing the lightest new state to decay so that it is no longer a dark matter candidate
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