An alternative NMSSM phenomenology with manifest perturbative unification

TL;DR

The work addresses whether NMSSM can accommodate a moderate stop mass without conflicting with LEP Higgs limits and while preserving manifest perturbative unification. It combines (i) a RG-based optimization of the SH1H2 coupling lambda, (ii) a simple 2×2 CP-even Higgs mixing analysis, and (iii) a concrete PQ-symmetric NMSSM (PQ SUSY) realization to illustrate the phenomenology. It finds that extra SU(5) multiplets at intermediate scales can raise the Higgs mass by up to ~20 GeV, with mixing adding a further few GeV, and that PQ SUSY predicts a light S1 decaying mainly via the pseudo-Goldstone G, plus a light G that couples to bb and tau tau; the scenario also implies characteristic neutralino decays to gravitino+G and a potentially observable Upsilon→γG signal in certain mass windows. The study demonstrates a concrete, testable NMSSM framework that maintains perturbative unification, offers distinctive collider and flavor signatures, and motivates further exploration of EWPT constraints and alternative NMSSM variants with additional symmetries.

Abstract

Can supersymmetric models with a moderate stop mass be made consistent with the negative Higgs boson searches at LEP, while keeping perturbative unification manifest? The NMSSM achieves this rather easily, but only if extra matter multiplets filling complete SU(5) representations are present at intermediate energies. As a concrete example which makes use of this feature, we give an analytic description of the phenomenology of a constrained NMSSM close to a Peccei-Quinn symmetry point. The related pseudo-Goldstone boson appears in decays of the Higgs bosons and possibly of the lightest neutralino, and itself decays into (b anti-b) and (tau anti-tau).

Figures (11)

• Figure 1: Lower (red) curve: the maximal value of $\lambda(M_{Z})$ as a function of $\tan\beta$ in NMSSM without extra matter at intermediate energies, subject to the condition $\lambda_{\mathrm{GUT}}/4\pi<0.3$, $\kappa_{\mathrm{GUT}}=0$. Upper (blue) curves: same but with $n_{5}=3$ extra $5+\bar{5}$ at 1 TeV, and $\lambda _{\mathrm{GUT}}/4\pi<0.3,0.15$.
• Figure 2: The maximal value of $m_{h}$, see Eq. (\ref{['mh']}), in NMSSM without extra matter (red) and with $n_{5}=3$ extra $5+\bar{5}$ at 1 TeV (blue). The values of $\lambda _{\mathrm{GUT}}$ are the same as in Fig. \ref{['lambdamax']}. The stop mass is fixed at $m_{\tilde{t}}=300$ GeV with moderate mixing, $\vert$$A_{t}/m_{\tilde{t}}|\lesssim1$ .
• Figure 3: For two reference values $m_{h}=110$ GeV (left) and $m_{h}=120$ GeV (right) we plot the normalized squared coupling, eq. (\ref{['xi']}), of the lightest scalar $h_{1}$ in the 2$\times$2 mixing model eq. (\ref{['2x2']}), plotted as a function of its mass $m_{1}$ and the mass of the heavier state $m_{2}$. The region below the lower blue (upper red) curve is consistent with the 95% C.L. bounds LEP2 from nonobservation of $h_{1}$ at LEP2, assuming it decays into $b\bar{b}$ ($b\bar{b}\,b\bar{b}$). The heavier scalar $h_{2}$, to be consistent with the LEP2 searches, should have the mass above $\sim114$ GeV.
• Figure 4: The allowed region of the $(m_{S},A_{\lambda})$ plane (see the text) for $\tan\beta=1.5,2,2.5$ and $\lambda$ fixed at $0.65,0.7,0.75$, respectively.
• Figure 5: The masses of the two lightest CP-even scalars in the model of Section \ref{['PQ']} for $(\lambda ,\tan{\beta},A_{\lambda})=(0.7,2,400~\mathrm{{GeV})}$ and a range of $m_{S}$ values consistent with global stability of the scalar potential. We include the stop quantum correction with $m_{\tilde{t}}=300$ GeV. The region to the right of the dashed line ($m_{S}>40$ GeV) is excluded by LEP constraints on the $S_{1}ZZ$ coupling (see Fig. \ref{['paramfinal']}).