A SM-like Higgs near 125 GeV in low energy SUSY: a comparative study for MSSM and NMSSM

TL;DR

This work evaluates whether a SM-like Higgs with mass near 125 GeV can be realized in low-energy SUSY, comparing MSSM and NMSSM under current experimental constraints. By scanning broad parameter spaces and computing rescaled Higgs couplings and production rates, the authors show that the NMSSM achieves the observed mass with less tuning and can naturally enhance di-photon and VV^* signals, while the MSSM relies on heavy stops and large A_t or light staus for modest enhancements. They also explore correlations with muon g-2 and dark matter, noting that XENON100 will soon probe a sizable portion of the NMSSM parameter space. Overall, the NMSSM emerges as the most natural and testable realization of a 125 GeV Higgs in low-energy SUSY, with distinctive predictions for collider and dark matter experiments.

Abstract

Motivated by the recent LHC hints of a Higgs boson around 125 GeV, we assume a SM-like Higgs with the mass 123-127 GeV and study its implication in low energy SUSY by comparing the MSSM and NMSSM. We consider various experimental constraints at 2-sigma level (including the muon g-2 and the dark matter relic density) and perform a comprehensive scan over the parameter space of each model. Then in the parameter space which is allowed by current experimental constraints and also predicts a SM-like Higgs in 123-127 GeV, we examine the properties of the sensitive parameters (like the top squark mass and the trilinear coupling A_t) and calculate the rates of the di-photon signal and the VV^* (V=W,Z) signals at the LHC. Our typical findings are: (i) In the MSSM the top squark and A_t must be large and thus incur some fine-tuning, which can be much ameliorated in the NMSSM; (ii) In the MSSM a light stau is needed to enhance the di-photon rate of the SM-like Higgs to exceed its SM prediction, while in the NMSSM the di-photon rate can be readily enhanced in several ways; (iii) In the MSSM the signal rates of pp -> h -> VV^* at the LHC are never enhanced compared with their SM predictions, while in the NMSSM they may get enhanced significantly; (iv) A large part of the parameter space so far survived will be soon covered by the expected XENON100(2012) sensitivity (especially for the NMSSM).

Figures (9)

• Figure 1: The scatter plots of the samples in the MSSM and NMSSM satisfying all the requirements (1-7) listed in the text (including $123{\rm GeV} \leq m_h \leq 127 {\rm GeV}$), projected in the plane of $m_{\tilde{t}_1}$ versus $X_t/M_{S}$ with $M_S \equiv \sqrt{m_{\tilde{t}_1} m_{\tilde{t}_2}}$ and $X_t \equiv A_t - \mu \cot \beta$.
• Figure 2: Same as Fig.1, except that the samples are based on the narrowed scan ranges of the soft masses shown in Eq.(\ref{['narrow']}) for both models and the requirement $\lambda > 0.53$ for the NMSSM. Here the samples are projected in the plane of $m_{\tilde{t}_1}$ versus $A_t$. The upper (lower) panels correspond to $R_{\gamma \gamma} < 1$ ($R_{\gamma \gamma} > 1$) with $R_{\gamma\gamma}\equiv \sigma_{SUSY} ( p p \to h \to \gamma \gamma)/\sigma_{SM} ( p p \to h \to \gamma \gamma )$. For the NMSSM results, the circles (green) denote the case of the lightest Higgs boson being the SM-like Higgs (the so-called pull-down case), and the times (red) denotes the case of the next-to-lightest Higgs boson being the SM-like Higgs (the so-called push-up case).
• Figure 3: Same as Fig.\ref{['fig2']}, but showing the dependence of the di-photon signal rate $R_{\gamma\gamma}$ on the effective $h b\bar{b}$ coupling $C_{h b\bar{b}}\equiv C^{\rm SUSY}_{h b\bar{b}}/C^{\rm SM}_{h b\bar{b}}$.
• Figure 4: Same as Fig.\ref{['fig2']}, but only for the MSSM, projected in the planes of $\tan\beta$ versus $\mu$ and $R_{\gamma \gamma}$ versus $m_{\tilde{\tau}_1}$.
• Figure 5: Same as Fig.\ref{['fig2']}, but showing the signal rate $R_{VV}\equiv \sigma_{\rm SUSY} ( p p \to h \to VV^\ast)/\sigma_{\rm SM} ( p p \to h \to VV^\ast)$ versus the coupling $C_{hVV}\equiv C^{\rm SUSY}_{hVV}/C^{\rm SM}_{hVV}$.