125 GeV Higgs boson, enhanced diphoton rate, and gaugedU(1)PQ-extended MSSM

Abstract

The ATLAS and CMS collaborations have announced discovery of a $\ensuremath{\sim}125\text{ }\text{ }\mathrm{GeV}$ Higgs boson, after a combined analysis of the diphoton 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 a non-decoupling a 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 $\ensuremath{\mu}$ 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 diphoton signal rate, $1.56\ifmmode\pm\else\textpm\fi{}0.43$ and $1.9\ifmmode\pm\else\textpm\fi{}0.5$ 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 diphoton signal rate can be enhanced significantly electroweak 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 diphoton rate. We also comment on possible signals of such light exotics at the LHC.