It's all right(-handed neutrinos): a new $W^{\prime }$ model for the $R_{D^{(\ast )}}$ anomaly

Abstract

The measured $B$-meson semi-leptonic branching ratios $R_D$ and $R_{D^{\ast }}$ have long-standing deviations between theory and experiment. We introduce a model which explains both anomalies through a single interaction by introducing a right-handed neutrino as the missing energy particle. This interaction is mediated by a heavy charged vector boson ($W^{\prime }$) which couples only to right-handed quarks and leptons of the Standard Model through the mixing of these particles with new vector-like fermions. Previous $W^{\prime }$ models for the $R_{D^{(\ast )}}$ anomaly were strongly constrained from flavor changing neutral currents and direct collider searches for $Z^{\prime }\to \ddot{I}„\ddot{I}„$ resonances. We show that relying on right-handed fermion mixing enables us to avoid these constraints, as well as other severe bounds from electroweak precision tests and neutrino mixing.

24 pages + appendix, 5 figures. v2: typos fixed, references added, minor updates, conclusions unchanged