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

TL;DR

This paper proposes a new $W'$ model with right-handed neutrinos to explain the $R_{D^{(*)}}$ anomalies, avoiding previous constraints from flavor physics and collider searches by using right-handed fermion mixing.

Contribution

It introduces a novel $W'$ model that accounts for $R_{D^{(*)}}$ anomalies via right-handed interactions, circumventing key experimental constraints.

Findings

The model successfully explains the $R_{D^{(*)}}$ anomalies.

It avoids flavor-changing neutral current constraints.

It remains consistent with collider and electroweak bounds.

Abstract

The measured $B$-meson semi-leptonic branching ratios $R_{D}$ and $R_{D^*}$ 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 ($W'$) 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 $W'$ models for the $R_{D^{(*)}}$ anomaly were strongly constrained from flavor changing neutral currents and direct collider searches for $Z'\to\tau\tau$ 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.