Jonathan P. Hall

Novel Higgs Decays and Dark Matter in the E(6)SSM

The Exceptional Supersymmetric (SUSY) Standard Model (E6SSM) predicts three families of Higgs doublets plus three Higgs singlets, where one family develops vacuum expectation values (VEVs), while the remaining two which do not are called Inert. The model can account for the dark matter relic abundance if the two lightest Inert neutralinos, identified as the (next-to) lightest SUSY particles ((N)LSPs), have masses close to half the Z mass. In this case we find that the usual SM-like Higgs boson decays more than 95% of the time into either LSPs or NLSPs. The latter case produces a final state containing two leptons l+l− with an invariant mass less than or about 10 GeV. We illustrate this scenario with a set of benchmark points satisfying phenomenological constraints and the WMAP dark matter relic abundance. This scenario also predicts other light Inert chargino and neutralino states below 200GeV, and large LSP direct detection cross-sections close to current limits and observable soon at XENON100. E-mail: jonathan.hall@soton.ac.uk. E-mail: s.f.king@soton.ac.uk. On leave of absence from the Theory Department, ITEP, Moscow, Russia; E-mail: nevzorov@phys.hawaii.edu. E-mail: pakvasa@phys.hawaii.edu. E-mail: mtsher@wm.edu.

Bino dark matter and big bang nucleosynthesis in the constrained E6SSM with massless inert singlinos

We discuss a new variant of the E6 inspired supersymmetric standard model (E6SSM) in which the two inert singlinos are exactly massless and the dark matter candidate has a dominant bino component. A successful relic density is achieved via a novel mechanism in which the bino scatters inelastically into heavier inert Higgsinos during the time of thermal freeze-out. The two massless inert singlinos contribute to the effective number of neutrino species at the time of Big Bang Nucleosynthesis, where the precise contribution depends on the mass of the Z′ which keeps them in equilibrium. For example for mZ′ > 1300 GeV we find Neff ≈ 3.2, where the smallness of the additional contribution is due to entropy dilution. We study a few benchmark points in the constrained E6SSM with massless inert singlinos to illustrate this new scenario.

Nonstandard Higgs decays in the E 6 SSM

We study the nonstandard decays of the lightest Higgs state within the Exceptional Supersymmetric Standard Model (E6SSM). We argued that the SM‐like Higgs boson can decay predominantly into dark matter particles while its branching ratios into S M particles varies from 2% to 4%. This scenario also implies the presence of other relatively ligh t Inert chargino and neutralino states in the particle spectrum with masses below 200 GeV. We argue that in this case the decays of the lightest Higgs boson into l + l − + X may play an essential role in the Higgs searches.

Novel gluino cascade decays in

We point out that the extra neutralinos and charginos, generically appearing in a large class of

E_6

E_6

inspired models

inspired models, lead to distinctive signatures from gluino cascade decays involving longer decay chains, more visible transverse energy, softer jets and leptons and less missing transverse energy than in the Minimal Supersymmetric Standard Model (MSSM). On the one hand, this makes the gluino harder to discover for certain types of conventional analysis. On the other hand, the

Discovering

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E_6

inspired models have enhanced 3- and 4-lepton signatures, as compared to the MSSM, making the gluino more visible in these channels. After extensive scans over the parameter space, we focus on representative benchmark points for the two models, and perform a detailed Monte Carlo analysis of the 3-lepton channel, showing that

supersymmetric models in gluino cascade decays at the LHC

E_6

E6SSM vs MSSM gluino phenomenology

inspired models are clearly distinguishable from the MSSM in gluino cascade decays.