We examine the possibility of electroweak baryogenesis and dark matter in the nMSSM, a minimal extension of the MSSM with a singlet field. This extension avoids the usual domain wall problem of the NMSSM, and also appears as the low energy theory in models of dynamical electroweak symmetry breaking with a so-called fat-Higgs boson. We demonstrate that a strong, first order electroweak phase transition, necessary for electroweak baryogenesis, may arise in regions of parameter space where the lightest neutralino provides an acceptable dark matter candidate. We investigate the parameter space in which these two properties are fulfilled and discuss the resulting phenomenology. In particular, we show that there are always two light CPeven and one light CP-odd Higgs bosons with masses smaller than about 250 GeV. Moreover, in order to obtain a realistic relic density, the lightest neutralino mass tends to be smaller than M Z /2, in which case the lightest Higgs boson decays predominantly into neutralinos.

We present a new strategy to uncover light, quasi-degenerate Higgsinos, a likely ingredient in a natural supersymmetric model. Our strategy focuses on Higgsinos with inter-state splittings of O(5 − 50) GeV that are produced in association with a hard, initial state jet and decay via off-shell gauge bosons to two or more leptons and missing energy, pp → j + / E T + 2 + . The additional jet is used for triggering, allowing us to significantly loosen the lepton requirements and gain sensitivity to small inter-Higgsino splittings. Focusing on the two-lepton signal, we find the seemingly large backgrounds from diboson plus jet,tt and Z/γ * + j can be reduced with careful cuts, and that fake backgrounds appear minor. For Higgsino masses mχ just above the current LEP II bound (µ 110 GeV) we find the significance can be as high as 3 σ at the LHC using the existing 20 fb −1 of 8 TeV data. Extrapolating to LHC at 14 TeV with 100 fb −1 data, and as one example M1 = M2 = 500 GeV, we find 5 σ evidence for mχ 140 GeV and 2 σ evidence for mχ 200 GeV. We also present a reinterpretation of ATLAS/CMS monojet bounds in terms of degenerate Higgsino (δmχ 5 GeV) plus jet production. We find the current monojet bounds on mχ are no better than the chargino bounds from LEP II.

The Minimal Supersymmetric extension of the Standard Model (MSSM) can provide the correct neutralino relic abundance and baryon number asymmetry of the universe. Both may be efficiently generated in the presence of CP violating phases, light charginos and neutralinos, and a light top squark. Due to the coannihilation of the neutralino with the light stop, we find a large region of parameter space in which the neutralino relic density is consistent with WMAP and SDSS data. We perform a detailed study of the additional constraints induced when CP violating phases, consistent with the ones required for baryogenesis, are included. We explore the possible tests of this scenario from present and future electron Electric Dipole Moment (EDM) measurements, direct neutralino detection experiments, collider searches and the b → sγ decay rate. We find that the EDM constraints are quite severe and that electron EDM experiments, together with stop searches at the Tevatron and Higgs searches at the LHC, will provide a definite test of our scenario of electroweak baryogenesis in the next few years.