Abstract

LHCb’s recent measurements of certain semi-leptonic B meson decays deviate from the Standard Model prediction at the level of four sigma. If this deviation is confirmed with the release of more data from LHCb and B factory experiments, this would strongly imply the existence of new physics which couples differently to muons and electrons. It is tempting to hypothesize that such flavour-dependent new physics could also explain the hierarchies in fermion masses. To that end, in this talk I will introduce the “Third Family Hypercharge Model” which explains both the LHCb data and the hierarchical heaviness of the third family via an anomaly-free, spontaneously-broken U(1) gauge symmetry, without any fermionic fields beyond those of the Standard Model. The charges of the third family fermions and the Standard Model Higgs are set equal to their respective hypercharges, with the lighter fermions being uncharged under the new U(1) symmetry. I will illustrate how the model is consistent with experimental bounds (for example, from precision LEP measurements) in a simple example case.