A Higgs boson near 125 GeV with enhanced di-photon signal in the NMSSM

TL;DR

The paper addresses how the NMSSM can accommodate a CP-even Higgs near $M_H \approx 125$ GeV with an enhanced di-photon signal through strong $H_{SM}-S$ mixing, avoiding excessive radiative corrections. It analyzes a natural region of NMSSM parameter space with a scale-invariant superpotential, performing scans that show $H_2$ can lie at $M_{H_2}\in [124,127]$ GeV and exhibit $R_2^{\gamma\gamma}>1$ due to a reduced $b\bar{b}$ width, while a lighter $H_1$ remains in the $70-120$ GeV range. The study identifies specific parameter correlations (e.g., $0.5<\lambda<0.6$, $0.3<\kappa<0.4$, $A_\kappa\sim-200$ to $-250$ GeV) and uses NMSSMTools to enforce LEP and B-physics constraints. Overall, the work provides testable predictions: an enhanced di-photon rate for the $H_2$ candidate and potential signals from a lighter $H_1$, offering concrete paths to distinguish this NMSSM scenario from the SM and MSSM with current and future LHC data.

Abstract

A natural region in the parameter space of the NMSSM can accomodate a CP-even Higgs boson with a mass of about 125 GeV and, simultaneously, an enhanced cross section times branching ratio in the di-photon channel. This happens in the case of strong singlet-doublet mixing, when the partial width of a 125 GeV Higgs boson into bb is strongly reduced. In this case, a second lighter CP-even Higgs boson is potentially also observable at the LHC.

Figures (2)

• Figure 1: The relative signal rate $R_2^{\gamma\gamma} = \sigma_2^{\gamma\gamma}/\sigma_{SM}^{\gamma\gamma}$ as function of $S_{2,d}^2$, for $H_2$ with a mass in the $124 - 127$ GeV range for about 550 points in the parameter space of the NMSSM described in the text
• Figure 2: The relative signal rate $R_1=R_1^{\gamma\gamma} = \sigma_1^{\gamma\gamma}/\sigma_{SM}^{\gamma\gamma}$ (red triangles) and $R_1=R_1^{\tau\tau} = \sigma_1^{\tau\tau}/\sigma_{SM}^{\tau\tau}$ (black crosses) as function of $M_{H_1}$, for about 550 points in the parameter space of the NMSSM described in the text