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Register a new userNeutralinos and Higgs Bosons in the Next-To-Minimal Supersymmetric Standard Model
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The purpose of this paper is to present a complete and consistent list of the Feynman rules for the vertices of neutralinos and Higgs bosons in the Next-To-Minimal Supersymmetric Standard Model (NMSSM), which does not yet exist in the literature. The Feynman rules are derived from the full expression for the Lagrangian and the mass matrices of the neutralinos and Higgs bosons in the NMSSM. Some crucial differences between the vertex functions of the NMSSM and the Minimal Supersymmetric Standard Model (MSSM) are discussed.
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Within the framework of the Next-To-Minimal Supersymmetric Standard Model (NMSSM) we study neutralino production $e^+e^- longrightarrow tilde{chi}^0_i tilde{chi}^0_j$ ($i,j=1,ldots ,5$) at center-of-mass energies between 100 and 600 GeV and the decays of the heavier neutralinos into the LSP plus a fermion pair, a photon or a Higgs boson. For representative gaugino/higgsino mixing scenarios, where the light neutralinos have significant singlet components, we find some striking differences between the NMSSM and the minimal supersymmetric model. Since in the NMSSM neutralino and Higgs sector are strongly correlated, the decay of the second lightest neutralino into a Higgs boson and the LSP often is kinematically possible and even dominant in a large parameter region of typical NMSSM scenarios. Also, the decay rates into final states with a photon may be enhanced.
In the Next--To--Minimal Supersymmetric Standard Model (NMSSM), the Higgs and neutralino/chargino sectors are strongly correlated by four common parameters at tree level. Therefore we analyze the experimental data from both the search for Higgs bosons as well as for neutralinos and charginos at LEP 100 in order to constrain the parameter space and the masses of the neutral Higgs particles in the NMSSM. We find that small singlet vacuum expectation values are ruled out, but a massless neutral Higgs scalar and pseudoscalar is not excluded for most of the parameter space of the NMSSM. Improved limits from the neutralino/chargino search at LEP 200, however, may lead to nonvanishing lower Higgs mass bounds.
We consider the fully constrained version of the next-to-minimal supersymmetric extension of the standard model (cNMSSM) in which a singlet Higgs superfield is added to the two doublets that are present in the minimal extension (MSSM). Assuming universal boundary conditions at a high scale for the soft supersymmetry-breaking gaugino, sfermion and Higgs mass parameters as well as for the trilinear interactions, we find that the model is more constrained than the celebrated minimal supergravity model. The phenomenologically viable region in the parameter space of the cNMSSM corresponds to a small value for the universal scalar mass m_0: in this case, one single input parameter is sufficient to describe the phenomenology of the model once the available constraints from collider data and cosmology are imposed. We present the particle spectrum of this very predictive model and discuss how it can be distinguished from the MSSM.
The phenomenology of the explicit CP violation in the Higgs sector of the next-to-minimal supersymmetric standard model (NMSSM) is investigated, with emphasis on the charged Higgs boson. The radiative corrections due to both quarks and scalar-quarks of the third generation are taken into account, and the negative result of the search for the Higgs bosons at CERN LEP2, with the discovery limit of 0.1 pb, is imposed as a constraint. It is found that there are parameter regions of the NMSSM where the lightest neutral Higgs boson may even be massless, without being detected at LEP2. This implies that the LEP2 data do not contradict the existence of a massless neutral Higgs boson in the NMSSM. For the charged Higgs boson, the radiative corrections to its mass may be negative in some parameter regions of the NMSSM. The phenomenological lower bound on the radiatively corrected mass of the charged Higgs boson is increased as the CP violation becomes maximal, i.e., as the CP violating phase becomes $pi/2$. At the maximal CP violation, its lower bound is about 110 GeV for 5 $leqslant tan beta leqslant$ 40. The vacuum expectation value (VEV) of the neutral Higgs singlet is shown to be no smaller than 16 GeV for any parameter values of the NMSSM with explicit CP violation. This value of the lower limit is found to increase up to about 45 GeV as the ratio ($tan beta$) of the VEVs of the two Higgs doublets decreases to smaller values ($sim$ 2). The discovery limit of the Higgs boson search at LEP2 is found to cover about a half of the kinematically allowed part of the whole parameter space of the NMSSM, and the portion is roughly stable against the CP violating phase.
We analyze the experimental data from the search for new particles at LEP 100 and obtain mass bounds for the neutralinos of the Next--To--Minimal Supersymmetric Standard Model (NMSSM). We find that for $tanbeta gsim 5.5$ a massless neutralino is still possible, while the lower mass bound for the second lightest neutralino corresponds approximately to that for the lightest neutralino in the Minimal Supersymmetric Standard Model (MSSM).
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