125 GeV Higgs Boson, Enhanced Di-photon Rate, and Gauged U(1)_PQ-Extended MSSM

TL;DR

This paper explores how extending the MSSM with a gauged U(1)_PQ symmetry can raise the Higgs mass and enhance the di-photon decay rate, aligning with recent experimental observations.

Contribution

It introduces a U(1)_PQ-extended MSSM model that explains the Higgs mass and di-photon rate enhancements while satisfying experimental constraints.

Findings

The model can naturally accommodate a 125 GeV Higgs.

Enhanced di-photon signal rates are achievable with light charged exotics.

Two benchmark scenarios demonstrate viable parameter spaces.

Abstract

The ATLAS and CMS collaborations have announced discovery of a ~125 GeV Higgs boson, after a combined analysis of the di-photon and ZZ search channels. This observation has significant impact on low-energy supersymmetry. First, some fine-tuning is necessary to accommodate such a Higgs mass in the Minimal Supersymmetric Standard Model (MSSM) because the tree-level mass of the SM-like Higgs boson in the MSSM is relatively small. We study the possibility of lifting the mass of the SM-like Higgs boson by non-decoupling D-term from an additional U(1) gauge symmetry. In particular, we focus on a gauged Peccei-Quinn symmetry which can also be related to a possible solution of the mu problem in the MSSM. In addition to the measurement of the mass of the Higgs, the data also reveals a tantalizing hint of a significantly enhanced di-photon signal rate, 1.56 pm 0.43 and 1.9 pm 0.5 times of the SM prediction in the CMS and ATLAS experiments, respectively. We demonstrate that such an enhancement can be accommodated in this MSSM extension. Anomaly cancellation requires the introduction of charged exotics. If some of them happen to be light and have sizable coupling to the SM-like Higgs boson, the di-photon signal rate can be enhanced significantly. EW precision measurements provide stringent constraints on this model. Taking these into account, we identify two benchmark scenarios. We argue that they are representative of large classes of viable models beyond our current example which can consistently enhance the Higgs to di-photon rate. We also comment on possible signals of such light exotics at the LHC.