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Supersymmetric dark matter has been studied extensively in the context of the MSSM, where gauginos have Majorana masses. Introducing Dirac gaugino masses, we obtain an enriched phenomenology from which considerable differences in, e.g., LHC signatures can be expected. Concretely, in the Minimal Dirac Gaugino Model (MDGSSM) we have an electroweakino sector extended by two extra neutralinos and one extra chargino. The bino- and wino-like states bring about small mass splittings leading to the frequent presence of scenarios with Long Lived Particles (LLPs). In this contribution, we delineate the parameter space of the electroweakino sector of the MDGSSM, where the lightest neutralino is a viable dark matter candidate that escapes current dark matter direct detection. We then focus on the allowed regions that contain LLPs and confront them against the corresponding LHC searches. Finally, we discuss the predominant case of long-lived neutralinos, to which no search is currently sensitive.
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In the supersymmetric (SUSY) standard model, the lightest neutralino may be the lightest SUSY particle (LSP), and it is is a candidate of the dark matter in the universe. The LSP dark matter might be produced by the non-thermal process such as heavy particle decay after decoupling of the thermal relic LSP. If the produced LSP is relativistic, and does not scatter enough in the thermal bath, the neutralino LSP may contribute as the warm dark matter (WDM) to wash out the small scale structure of O(0.1) Mpc. In this letter we calculate the energy reduction of the neutralino LSP in the thermal bath and study whether the LSP can be the WDM. If temperature of the production time T_I is smaller than 5MeV, the bino-like LSP can be the WDM and may contribute to the small-scale structure of O(0.1) Mpc. The Higgsino-like LSP might also work as the WDM if T_I< 2MeV. The wino-like LSP cannot be the WDM in the favoured parameter region.
In spite of rapid experimental progress, windows for light superparticles remain. One possibility is a ~100 GeV tau slepton whose t-channel exchange can give the correct thermal relic abundance for a relatively light neutralino. We pedagogically review how this region arises and identify two distinct scenarios that will be tested soon on multiple fronts. In the first, the neutralino has a significant down-type higgsino fraction and relatively large rates at direct detection experiments are expected. In the second, there is large mixing between two relatively light staus, which could lead to a significant excess in the Higgs boson branching ratio to photons. In addition, electroweak superpartners are sufficiently light that direct searches should be effective.
Neutralino dark matter, and in particular different aspects of its detection at neutrino telescopes, has been studied within the Minimal Supersymmetric extension of the Standard Model, the MSSM. The relic density of neutralinos has been calculated using sophisticated routines for integrating the annihilation cross section and the Boltzmann equation. As a new element, so called coannihilation processes between the lightest neutralino and the heavier neutralinos and charginos have also been included for any neutralino mass and composition. The detection rates at neutrino telescopes have been evaluated for neutralino annihilation in both the Sun and the Earth using detailed Monte Carlo simulations of the whole chain of processes from the neutralino annihilation products in the core of the Sun or the Earth to detectable muons at a neutrino telescope. A comparison with other searches for supersymmetry at accelerators and direct dark matter searches is also given. The signal muon fluxes that current and future neutrino telescopes can probe and the improvement in sensitivity that can be achieved with angular and/or energy resolution of the neutrino-induced muons has also been investigated. The question of whether the neutralino mass can be extracted from the width of the muon angular distribution, if a signal flux is observed, has also been addressed.
The direct detection of neutralino dark matter is analysed in general supergravity scenarios, where non-universal soft scalar and gaugino masses can be present. In particular, the theoretical predictions for the neutralino-nucleon cross section are studied and compared with the sensitivity of dark matter detectors. We take into account the most recent astrophysical and experimental constraints on the parameter space, including the current limit on B(Bs-> mu+ mu-). The latter puts severe limitations on the dark matter scattering cross section, ruling out most of the regions that would be within the reach of present experiments. We show how this constraint can be softened with the help of appropriate choices of non-universal parameters which increase the Higgsino composition of the lightest neutralino and minimise the chargino contribution to the b->s transition.
We study the scenario of gravitino DM with a general neutralino NLSP in a model independent way. We consider all neutralino decay channels and compare them with the most recent BBN constraints. We check how those bounds are relaxed for a Higgsino or a Wino NLSP in comparison to the Bino neutralino case and look for possible loopholes in the general MSSM parameter space.We determine constraints on the gravitino and neutralino NLSP mass and comment on the possibility of detecting these scenarios at colliders.
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