Minimal flavor-changing $Z^\prime$ models and muon $g−2$ after the $R_{K^\star}$ measurement


There has been a steady interest in flavor anomalies and their global fits as ideal probes of new physics. If the anomalies are real, one promising explanation is a new $Z^\prime$ gauge boson with flavor-changing coupling to bottom and strange quarks and a flavor-conserving coupling to muons and, possibly, electrons. We point out that direct production of such a $Z^\prime$, emerging from the collision of $b$ and $s$ quarks, may offer a complementary window into these phenomena because collider searches already provide competitive constraints. On top of that, we analyse the same $Z^\prime$ scenario in relation to another long-standing discrepancy between theory and experiment that concerns the anomalous magnetic moment of the muon. By scanning the allowed $Z^\prime$ coupling strengths in the low-mass region, we assess the compatibility of the signals from LHCb with the $Z^\prime$ searches in the high energy LHC data and the measurements of the anomalous magnetic moment of the involved leptons. We also argue that observations of the latter can break the degeneracy pattern in the Wilson coefficients $C_9$ and $C_{10}$ presented by LHCb data. The $Z^\prime$ model we consider is compatible with the new measurement of $R_{K^\star}$, therefore it can potentially account for the long-standing deviations observed in $B$-physics.

Nucl.Phys. B923 (2017) 245-257