Unified explanation of the anomalies in semileptonic B decays and the W mass

Abstract

The discrepancies between the measurements of rare (semi)leptonic B decays and the corresponding Standard Model predictions point convincingly toward the existence of new physics for which a heavy neutral gauge boson (Z′) is a prime candidate. However, the effect of the mixing of the Z′ with the SM Z, even though it cannot be avoided by any symmetry, is usually assumed to be small and thus neglected in phenomenological analyses. In this paper we point out that a mixing of the naturally expected size leads to lepton flavor universal contributions, providing a very good fit to B data. Furthermore, the global electroweak fit is affected by Z−Z′ mixing where the tension in the W mass, recently confirmed and strengthened by the CDF measurement, prefers a nonzero value of it. We find that a Z′ boson with a mass between ≈1–5  TeV can provide a unified explanations of the B anomalies and the W mass. This strongly suggest that the breaking of the new gauge symmetry giving raise to the Z′ boson is linked to electroweak symmetry breaking with intriguing consequences for model building.