Oct 2016 - Sep 2017

Thoughts on B-physics anomalies

by Sebastian Jäger (Sussex University)

Thursday, 27 April 2017 from to (Europe/London)
Rare B decays provide very sensitive probes of physics beyond the Standard Model. Very recently, LHCb has reported measurements of new lepton-universality-violating (LUV) observables in B->K* l l decays, complementing earlier measurements of lepton-universality violation in B->K l l and in B->D(*) tau nu decays, all of which differ from SM expectations.  I will explain the need for a modified, lepton-flavour-specific Wilson coefficient C10 (axial lepton coupling) to accommodate the most recent data and propose three further LUV ratios which are precise probes of the ratio C10mu/C10e. I then will argue that although the global fit favours, in addition, a sizable BSM effect in C9 (vectorial lepton coupling), this can perfectly well be lepton-flavour-universal. I discuss an efficient mechanism for generating it from b->c cbar s 4-fermion operators, which in turn contribute in a peculiar pattern to radiative decay and B meson lifetime observables. The scenario appears to be entirely viable and provides model-independent connections, between rare B decays and lifetime observables, and the potential to observe the same new physics in both.