Higgs Sector in Extensions of the MSSM

TL;DR

This work analyzes the neutral Higgs sector in MSSM extensions that introduce a singlet to dynamically generate the μ-parameter. It demonstrates that one-loop corrections are largely model-independent within these extensions, while tree-level parameters encode the model-specific structure, leading to diverse Higgs spectra and decays. By applying LEP and precision constraints, the authors show extended models can accommodate lighter or heavier Higgs states than the MSSM, with distinctive production and decay patterns driven by singlet mixing and potential non-SM channels. The study provides guidance on distinguishing NMSSM, nMSSM, UMSSM, and sMSSM via masses, couplings, and collider signatures such as non-SM decays and altered gamma-gamma rates.

Abstract

Extensions of the Minimal Supersymmetric Standard Model (MSSM) with additional singlet scalar fields solve the important mu-parameter fine tuning problem of the MSSM. We compute and compare the neutral Higgs boson mass spectra, including one-loop corrections, of the following MSSM extensions: Next-to-Minimal Supersymmetric Standard Model (NMSSM), the nearly-Minimal Supersymmetric Standard Model (nMSSM), and the U(1)'-extended Minimal Supersymmetric Standard Model (UMSSM) by performing scans over model parameters. We find that the Secluded U(1)'-extended Minimal Supersymmetric Standard Model (sMSSM) is identical to the nMSSM if three of the additional scalars decouple. The dominant part of the one-loop corrections are model-independent since the singlet field does not couple to MSSM particles other than the Higgs doublets. Thus, model-dependent parameters enter the masses only at tree-level. We apply constraints from LEP bounds on the Standard Model and MSSM Higgs boson masses and the MSSM chargino mass, the invisible Z decay width, and the Z-Z' mixing angle. Some extended models permit a Higgs boson with mass substantially below the SM LEP limit or above theoretical limits in the MSSM. Ways to differentiate the models via masses, couplings, decays and production of the Higgs bosons are discussed.

Figures (15)

• Figure 1: Lightest CP-even and lightest CP-odd Higgs masses vs. $\tan\beta$ and $s$ for the MSSM, NMSSM, n/sMSSM, UMSSM, and the PQ limits. Only the theoretical constraints are applied with $s = 500$ GeV (for $\tan\beta$-varying curves), $\tan\beta = 2$ (for $s$-varying curves). Input parameters of $A_s = 500$ GeV, $A_t = 1$ TeV, $M_{\tilde{Q}} = M_{\tilde{U}} = 1$ TeV, $\kappa = 0.5$, $A_\kappa = -250$ GeV, $M_{\rm n}=500$ GeV, $\xi_F = -0.1$, $\xi_S = -0.1$, $h_s = 0.5$, $\theta_{E6} = -\tan^{-1}\sqrt{5\over3}$, and $Q = 300$ GeV, the renormalization scale, are taken. The $U(1)_{PQ}$ limit allows one massive CP-odd Higgs whose mass is equivalent to that of the UMSSM CP-odd Higgs.
• Figure 2: Mass ranges of the lightest CP-even and CP-odd and the charged Higgs bosons in each extended-MSSM model from the grid and random scans. Explanation of extremal bounds and their values are provided for each model. Explanations are Th. - theoretical bound met, value not sensitive to limits of the scan parameters; Scan - value sensitive to limits of the scan parameters; State Crossing - value has maximum when crossing of states occurs (specifically for $A_1$ and $A_2$ in the NMSSM and n/sMSSM); LEP - experimental constraints from LEP; $\alpha_{ZZ'}$ - experimental constraints in the UMSSM on the $Z-Z'$ mixing angle.
• Figure 3: (a) LEP limit Sopczak:2005mc on $\xi_{ZZH_i} = \left({g_{ZZH_i} / g^{SM}_{ZZh}}\right)^2 = \Gamma_{Z \to Z H_i}/\Gamma^{SM}_{Z\to Zh}$, the scaled $ZZH_i$ coupling in new physics, vs. the light Higgs mass. The solid black curve is the observed limit with a 95% C. L. Points falling below this curve pass the $ZZH_i$ constraint. (b) $\cos^2(\beta-\alpha)$ vs. $M_{A_2}$ in the MSSM. The hard cutoff shown by the solid green line at $M_{A_2} = 93.4$ GeV is due to the constraint on $\sigma(e^+ e^- \to A_i H_1)$ discussed in Section \ref{['sect:dirlimits']}.
• Figure 4: Higgs masses vs. $\xi_{\text{MSSM}}$ in the (a) NMSSM, (b) n/sMSSM, (c) UMSSM and (d) the lightest CP-even Higgs of all extended models. The vertical line is the LEP lower bound on the MSSM (SM-like) Higgs mass.
• Figure 5: Higgs mass dependence on $\xi_S$ in the n/sMSSM. When $\xi_S\sim -0.1$, $H_2$ and $H_1$ switch content, allowing a light CP-even Higgs below the LEP limit.