Singlet-doublet Higgs mixing and its implications on the Higgs mass in the PQ-NMSSM

TL;DR

This paper investigates how singlet-doublet Higgs mixing in the PQ-NMSSM affects the Higgs boson mass and its collider signals, highlighting its potential to achieve a 125 GeV Higgs without relying heavily on stop mixing.

Contribution

It demonstrates that Higgs mixing in the PQ-NMSSM can raise the SM-like Higgs mass by a few GeV, even with minimal NMSSM contributions and near-SM signal rates.

Findings

Higgs mixing can increase the Higgs mass by a few GeV.

Higgs mixing can reduce the need for large stop mixing.

The model avoids tadpole and domain-wall problems.

Abstract

We examine the implications of singlet-doublet Higgs mixing on the properties of a Standard Model (SM)-like Higgs boson within the Peccei-Quinn invariant extension of the NMSSM (PQ-NMSSM). The SM singlet added to the Higgs sector connects the PQ and visible sectors through a PQ-invariant non-renormalizable K\"ahler potential term, making the model free from the tadpole and domain-wall problems. For the case that the lightest Higgs boson is dominated by the singlet scalar, the Higgs mixing increases the mass of a SM-like Higgs boson while reducing its signal rate at collider experiments compared to the SM case. The Higgs mixing is important also in the region of parameter space where the NMSSM contribution to the Higgs mass is small, but its size is limited by the experimental constraints on the singlet-like Higgs boson and on the lightest neutralino constituted mainly by the singlino whose Majorana mass term is forbidden by the PQ symmetry. Nonetheless the Higgs mixing can increase the SM-like Higgs boson mass by a few GeV or more even when the Higgs signal rate is close to the SM prediction, and thus may be crucial for achieving a 125 GeV Higgs mass, as hinted by the recent ATLAS and CMS data. Such an effect can reduce the role of stop mixing.