# Muon $g-2$ in a $U\left(1\right)$-symmetric two-Higgs-doublet model

Li, Shao-Ping (Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei 430079, People’s Republic of China) ; Li, Xin-Qiang (Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei 430079, People’s Republic of China) ; Yang, Ya-Dong (Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE), Central China Normal University, Wuhan, Hubei 430079, People’s Republic of China)

11 February 2019

Abstract: We show in this paper that, in a $U\left(1\right)$-symmetric two-Higgs-doublet model, the two additional neutral Higgs bosons would become nearly degenerate in the large $\mathrm{tan}\beta$ regime, under the combined constraints from both theoretical arguments and experimental measurements. As a consequence, the excess observed in the anomalous magnetic moment of the muon could not be addressed in the considered framework, following the usual argument where these two neutral scalars are required to manifest a large mass hierarchy. On the other hand, we find that, with an $O\left(1\right)$ top-Yukawa coupling and a relatively light charged Higgs boson, large contributions from the two-loop Barr-Zee-type diagrams can account for the muon $g-2$ anomaly at the $1\sigma$ level, in spite of a large cancellation between the scalar and pseudoscalar contributions. Furthermore, the same scenario can survive the tight constraints from the $B$-physics observables.

Published in: Physical Review D 99 (2019)