Masses and Couplings of the Lightest Higgs Bosons in the (M+1)SSM

We study the upper limits on the mass of the lightest and second lightest CP even Higgs bosons in the (M+1)SSM, the MSSM extended by a gauge singlet. The dominant two loop contributions to the effective potential are included, which reduce the Higgs masses by 10 GeV. Since the coupling R of the lightest Higgs scalar to gauge bosons can be small, we study in detail the relations between the masses and couplings of both lightest scalars. We present upper bounds on the mass of a 'strongly' coupled Higgs (R > 1/2) as a function of lower experimental limits on the mass of a 'weakly' coupled Higgs (R < 1/2). With the help of these results, the whole parameter space of the model can be covered by Higgs boson searches.Comment: Changed notation and added explanations; to appear in European Journal of Physics

Neutralino Cascades in the (M+1)SSM

In the (M+1)SSM an additional gauge singlet Weyl spinor appears in the neutralino sector. For a large part of the parameter space this approximative eigenstate is the true LSP. Then most sparticle decays proceed via an additional cascade involving the NLSP -> LSP transition, where the NLSP is the non-singlet next-to-lightest neutralino. We present a comprehensive list of all processes, which contribute to the NLSP -> LSP transition, the partial widths and the total NLSP decay rate. We perform a scan of the parameters of the model compatible with universal soft terms, and find that the NLSP life time can be quite large, leading to macroscopically displaced vertices. Our results imply that the signatures for sparticle production in the (M+1)SSM can be very different from the MSSM, and are important for calculations of the abundance of dark matter in this model.Comment: 25 pages (LaTeX2e), 8 figs., explanations adde

Topologies of the (M+1)SSM with a Singlino LSP at LEP2

We study the possible signals of the (M+1)SSM with a singlino LSP at LEP2. First we identify regions of the parameter space which are ruled out by negative results of sparticle searches in the context of the MSSM. In the remaining kinematically accessible regions we present total event rates for topologies which require further studies, i.e. estimations of the corresponding efficiencies: various 4 charged fermion final states with missing energy, possibly with displaced vertices due to a long lifetime of the NLSP, the second lightest neutralino. Searches for these unconventional signatures are essential in order to cover the entire kinematically accessible parameter space of the (M+1)SSM with a singlino LSP at LEP2.Comment: 21 pages (LaTeX2e), 2 figs., table with all possible final states adde

NMSSM Higgs Discovery at the LHC

We demonstrate that Higgs discovery at the LHC is possible in the context of the NMSSM even for those scenarios such that the only strongly produced Higgs boson is a very SM-like CP-even scalar which decays almost entirely to a pair of relatvely light CP-odd states. In combination with other search channels, we are on the verge of demonstrating that detection of at least one of the NMSSM Higgs bosons is guaranteed at the LHC for accumulated luminosity of $300 {\rm fb}^{-1}$.Comment: 8 pages, 1 figure, to appear in the Proceedings of the Les Houches Workshop 2003: ``Physics at TeV Colliders'

Reinforcing the no-lose theorem for NMSSM Higgs discovery at the LHC

We show the potential of the LHC to detect a CP-even Higgs boson of the NMSSM, $h_1$ or $h_2$, decaying into two rather light CP-odd Higgs bosons, $a_1$, by exploiting the production mode based on Higgs-strahlung off $b$-quarks, i.e., the channel $pp\to b\bar b h_{1,2}$. We also consider the case of $h_2\to h_1 h_1$ decays. It is found that these decays have dominant BRs over large regions of the NMSSM parameter space where tan$\beta$ is large, a condition which also favours the $pp\to b\bar b h_{1,2}$ production rates. Further decays of the light Higgs boson pairs ($a_1$ and $h_1$) into photon, muon, tau and $b$ final states are also considered. The overall production and decay rates for these processes at inclusive level are sizable and should help extracting at least one Higgs boson signal over the NMSSM parameter space.Comment: 19 pages, 9 figures, added comments and corrected typo

Relic density of dark matter in the NMSSM

We present a code to compute the relic density of dark matter in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Dominant corrections to the Higgs masses are calculated with NMHDECAY as well as theoretical and collider constraints. All neutralino annihilation and coannihilation processes are then computed with an extended version of micrOMEGAs, taking into acount higher order corrections to Higgs vertices. We explore the parameter space of the NMSSM and consider in particular the case of a bino LSP, of a mixed bino-higgsino LSP and of a singlino LSP. As compared to the MSSM, neutralino annihilation is often more efficient as it can take place via (additional) Higgs resonances as well as annihilation into light Higgs states. Models with a large singlino component can be compatible with WMAP constraints.Comment: 25 pages, 8 figures; one reference added and minor change in acknowledgement

Dark Matter in a Constrained NMSSM

We explore the parameter space of a Constrained Next-to-Minimal Supersymmetric Standard Model with GUT scale boundary conditions (CNMSSM) and find regions where the relic density of the lightest neutralino is compatible with the WMAP measurement. We emphasize differences with the MSSM: cases where annihilation of the LSP occurs via a Higgs resonance at low values of tan\beta and cases where the LSP has a large singlino component. The particle spectrum as well as theoretical and collider constraints are calculated with NMSSMTools. All neutralino annihilation and coannihilation processes are then computed with micrOMEGAs, taking into account higher order corrections to the Higgs sector.Comment: 17 pages, 6 figures, references added, some comments added, version to be published in JCA