Heavier $W$ boson, dark matter and gravitational waves from strings in an $SO(10)$ axion model

TL;DR

This paper explores an $SO(10)$ axion model that explains the recent $W$ boson mass measurement discrepancy, predicts dark matter candidates, and forecasts gravitational wave signals from cosmic strings.

Contribution

It introduces a scalar triplet in an $SO(10)$ model that adjusts the $W$ mass, compatible with unification and proton decay, and links to dark matter and gravitational wave predictions.

Findings

Triplet VEV significantly reduces $W$ mass discrepancy.

Model predicts observable proton decay and gauge coupling unification.

Cosmic strings produce a detectable gravitational wave spectrum.

Abstract

Inspired by the recent determination of the $W$-boson mass by the CDF collaboration, we revisit an $SO(10)$ axion model in which a scalar $SU(2)_L$ triplet field with zero hypercharge is known to acquire a non-zero VEV through its mixing with the Standard Model Higgs doublet. The triplet VEV provides a sizable contribution to the $W$ mass, which helps in significantly lowering the $7\sigma$ discrepancy between the Standard Model prediction and the higher CDF value for $m_W$. We show that the relatively light triplet mass ($\sim (1-50)$ TeV) is compatible with gauge coupling unification and observable proton decay. An unbroken $Z_2$ gauge symmetry, coupled with the presence of two fermionic $10$-plets required to resolve the axion domain wall problem, means that both axions and a stable intermediate mass ($\sim 10^9-10^{10}$ GeV) fermion are plausible dark matter candidates. We also display the gravitational wave spectrum from the intermediate scale topologically stable cosmic strings predicted by the model.