Singlet extensions and W boson mass in light of the CDF II result

Recently, the CDF collaboration has reported the precise measurement of the W boson mass, M-W = 80433.5 +/- 9.4MeV, based on 8.8 fb(-1) of root s = 1.96 TeV p (p) over bar collision data from the CDF II detector at the Fermilab Tevatron. This is about 7 sigma away from the Standard Model prediction, M-W(SM) = 80357 +/- 6 MeV. Such a large discrepancy may be partially due to exotic particles that radiatively alter the relation between the W and Z boson masses. In this Letter, we study singlet extensions of the Standard Model focusing on the shift of the W boson mass since they are accidentally flavor and CP safe without changing the Standard Model structure. In the minimal extension with a real singlet field, using the bounds from the electroweak oblique parameters, B meson decays, LEP, and LHC, we find that the W boson mass shift is at most a few MeV, and therefore it does not alleviate the tension between the CDF II result and the SM prediction. We then examine how much various bounds are relaxed when the singlet is allowed to decay invisibly, and find that the increase of the W boson mass does not exceed 5MeV due to the bound from the Higgs signal strength. We also discuss phenomenological and cosmological implications of the singlet extensions such as the muon g - 2 anomaly, axion/hidden photon dark matter, and self-interacting dark radiation as a possible alleviation of the Hubble tension. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

The CDF collaboration recently reported a precise measurement of the W boson mass, which shows a significant discrepancy from the Standard Model prediction. Their study on singlet extensions of the Standard Model revealed that even with invisible decay allowed for the singlet, the tension between the CDF II result and the SM prediction cannot be resolved.