CDF Multi-Muon Events and Singlet Extensions of the MSSM

We discuss a generalization of the minimal supersymmetric extension of the Standard Model in the form of three additional singlet superfields, which would explain the essential features of the CDF multi-muon events presented recently: a large production cross section of ~ 100 pb originates from the production of a CP-odd scalar A with a mass in the 70 - 80 GeV range and a large value of tan(beta) ~ 40. The CP-odd scalar A decays dominantly into CP-odd and CP-even scalars a_1 and h_1, which generate decay cascades h_1 -> 2 h_2 -> 4 a_2 -> 8 tau-leptons, and a_1 -> h_1 a_2 with h_1 decaying as above. The decay a_2 -> tau+ tau- is slow, leading to a lifetime of O(20) ps. The phenomenology of the model differs from similar scenarios presented before in that one of the two cascades leads to 10 instead of 8 tau-leptons, and additional production processes like associate A production with b b-bar pairs are relevant.Comment: 10 pages, comments on the required total cross section added, to appear in MPL

Modified Signals for Supersymmetry in the NMSSM with a Singlino-like LSP

In the framework of the NMSSM with a singlino-like LSP, we study quantitatively the impact of the additional bino -> singlino cascade on the efficiencies in several search channels for supersymmetry of the ATLAS and CMS collaborations. Compared to the MSSM, the additional cascade reduces the missing transverse energy, but leads to additional jets or leptons. For the NMSSM benchmark lines which generalize cMSSM benchmark points, the efficiencies in the most relevant 2/3 jet + missing energy search channels can drop by factors ~1/3 to ~1/7, and can reduce the present lower bounds on M_{1/2} by as much as ~0.9 - 0.75 in the NMSSM for large bino-singlino mass differences. The larger efficiencies in multijet or multilepton search channels are not strong enough to affect this conclusion. In the fully constrained cNMSSM, sparticle decay cascades via the lightest stau can lead to signal cross sections in multilepton and 2tau search channels which are potentially visible at the LHC with 7 TeV center of mass energy.Comment: 24 pages, 9 Figures, misprint in Table 1 correcre

Phenomenology of the General NMSSM with Gauge Mediated Supersymmetry Breaking

We investigate various classes of Gauge Mediated Supersymmetry Breaking models and show that the Next-to-Minimal Supersymmetric Standard Model can solve the mu-problem in a phenomenologically acceptable way. These models include scenarios with singlet tadpole terms, which are phenomenologically viable, e.g., in the presence of a small Yukawa coupling <~ 10^{-5}. Scenarios with suppressed trilinear A-terms at the messenger scale lead naturally to light CP-odd scalars, which play the r\^ole of pseudo R-axions. A wide range of parameters of such models satisfies LEP constraints, with CP-even Higgs scalars below 114 GeV decaying dominantly into a pair of CP-odd scalars.Comment: 24 pages, 6 figures, typos corrected, reference adde

Discovering the constrained NMSSM with tau leptons at the LHC

The constrained Next-to-Minimal Supersymmetric Standard Model (cNMSSM) with mSugra-like boundary conditions at the GUT scale implies a singlino-like LSP with a mass just a few GeV below a stau NLSP. Hence, most of the squark/gluino decay cascades contain two tau leptons. The gluino mass >~ 1.2 TeV is somewhat larger than the squark masses of >~ 1 TeV. We simulate signal and background events for such a scenario at the LHC, and propose cuts on the transverse momenta of two jets, the missing transverse energy and the transverse momentum of a hadronically decaying tau lepton. This dedicated analysis allows to improve on the results of generic supersymmetry searches for a large part of the parameter space of the cNMSSM. The distribution of the effective mass and the signal rate provide sensitivity to distinguish the cNMSSM from the constrained Minimal Supersymmetric Standard Model in the stau-coannihilation region.Comment: 18 pages, 3 Figure

Dark matter constraints on the parameter space and particle spectra in the nonminimal SUSY standard model

We investigate the dark matter constraints for the nonminimal SUSY standard model (NMSSM). The cosmologically restricted mass spectra of the NMSSM are compared to the minimal SUSY standard model (MSSM). The differences of the two models concerning the neutralino, sfermion and Higgs sector are discussed. The dark matter condition leads to cosmologically allowed mass ranges for the SUSY particles in the NMSSM: m_{\tilde{\chi}^0_1} < 300 GeV, m_{\tilde{e}_R} < 300 GeV, 300 GeV < m_{\tilde{u}_R} < 1900 GeV, 200 GeV < m_{\tilde{t}_1} < 1500 GeV, 350 GeV < m_{\tilde{g}} < 2100 GeV and for the mass of the lightest scalar Higgs m_{S_1} < 140 GeV.Comment: revised version to appear in Phys. Lett. B, 18 pages, LaTeX, 3 figures, uses epsfig.sty and amssymb.st

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

One-loop contribution to the neutrino mass matrix in NMSSM with right-handed neutrinos and tri-bimaximal mixing

Neutrino mass patterns and mixing have been studied in the context of next-to-minimal supersymmetric standard model (NMSSM) with three gauge singlet neutrino superfields. We consider the case with the assumption of R-parity conservation. The vacuum expectation value of the singlet scalar field $S$ of NMSSM induces the Majorana masses for the right-handed neutrinos as well as the usual $\mu$-term. The contributions to the light neutrino mass matrix at the tree level as well as one-loop level are considered, consistent with the tri-bimaximal pattern of neutrino mixing. Light neutrino masses arise at the tree level through a TeV scale seesaw mechanism involving the right-handed neutrinos. Although all the three light neutrinos acquire non-zero masses at the tree-level, we show that the one-loop contributions can be comparable in size under certain conditions.Comment: 14 pages, 7 figure

An origin for small neutrino masses in the NMSSM

We consider the Next to Minimal Supersymmetric Standard Model (NMSSM) which provides a natural solution to the so-called mu problem by introducing a new gauge-singlet superfield S. We realize that a new mechanism of neutrino mass suppression, based on the R-parity violating bilinear terms mu_i L_i H_u mixing neutrinos and higgsinos, arises within the NMSSM, offering thus an original solution to the neutrino mass problem (connected to the solution for the mu problem). We generate realistic (Majorana) neutrino mass values without requiring any strong hierarchy amongst the fundamental parameters, in contrast with the alternative models. In particular, the ratio |mu_i/mu| can reach about 10^-1, unlike in the MSSM where it has to be much smaller than unity. We check that the obtained parameters also satisfy the collider constraints and internal consistencies of the NMSSM. The price to pay for this new cancellation-type mechanism of neutrino mass reduction is a certain fine tuning, which get significantly improved in some regions of parameter space. Besides, we discuss the feasibility of our scenario when the R-parity violating bilinear terms have a common origin with the mu term, namely when those are generated via a VEV of the S scalar component from the couplings lambda_i S L_i H_u. Finally, we make comments on some specific phenomenology of the NMSSM in the presence of R-parity violating bilinear terms.Comment: 21 pages, 5 figures, Latex fil

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