Resolving ${\bf W}$ Boson Mass Shift and CKM Unitarity Violation in Left-Right Symmetric Models with Universal Seesaw

Abstract

We explore the possibility of resolving simultaneously the $W$-boson mass shift reported by the CDF collaboration and the apparent deviation from unitarity in the first row of the CKM mixing matrix in a class of left-right symmetric models. The fermion masses are generated in these models through a universal seesaw mechanism, utilizing vector-like partners of the usual fermions. We find a unique solution to the two anomalies where the mixing of the down quark with a vector-like quark (VLQ) resolves the CKM unitarity puzzle, and the mixing of the top quark with a VLQ partner explains the $W$ boson mass shift. The validity of this setup is tested against the stability of the Higgs potential up to higher energies. We find upper bounds of $(5,\,4,\,4)$ TeV on the masses of the down-type VLQ, the top-partner VLQ, and a neutral scalar associated with $SU(2)_R$ gauge symmetry breaking, respectively. This class of models can solve the strong CP problem via parity symmetry without the need for an axion.