Relaxing the Higgs mass bound in singlet extensions of the MSSM

TL;DR

This paper demonstrates that introducing a singlet coupling in the MSSM can significantly relax the Higgs mass upper bound, especially at large tan beta, by leveraging a UV complete model and radiative corrections.

Contribution

The paper constructs a UV complete model enabling large singlet-Higgs coupling at low energy, relaxing the Higgs mass bound in MSSM extensions at large tan beta.

Findings

Higgs mass can reach up to 130 GeV with large singlet-Higgs coupling.

The UV completion allows perturbativity at high scales.

Radiative corrections dominate the Higgs mass increase at large tan beta.

Abstract

We show that the upper bound on the lightest Higgs mass in the MSSM is relaxed by introducing a singlet which couples to the Higgs fields, even at a large tan beta region, preferable for explaining the muon anomalous magnetic moment. In the models of a singlet extension, it is known that the upper bound is relaxed by a tree-level contribution, especially at small tan beta region. For large tan beta, however, the requirement for the perturbativity on the singlet-Higgs coupling up to the GUT scale prevents the lightest Higgs from obtaining a large tree-level mass. We construct an explicit UV complete model which allows large singlet-Higgs coupling at low energy without disturbing the perturbativity. The UV completion can be applied for any singlet extension of the MSSM. Moreover, we point out that the radiative correction from the singlet-Higgs coupling becomes dominant, and the lightest Higgs mass can be easily as heavy as 130 GeV if this coupling is large enough even for large tan beta.