Enhancement of the W boson mass in the Georgi-Machacek model

Abstract

The recent CDF-II measurement of the mass of the W boson shows a significant tension with the Standard Model (SM) expectation, even when averaged with earlier measurements. The tension can be explained in the framework of any beyond-SM dynamics that contributes substantially to the oblique S and T parameters. As a typical example of such beyond-SM physics, we try to explain the tension in the framework of the Georgi-Machacek model that keeps ρ=1 at the tree-level, and explore the parameter space that can accommodate the W mass shift. We find that a sizeable split between the custodial triplet and 5-plet of scalars can help alleviate the tension to a large extent, and raise the W-mass by about 30 MeV over its SM value.