Celine Boehm, P. S. Bhupal Dev, Anupam Mazumdar, Ernestas Pukartas
We examine the possibility of a light (below 46 GeV) neutralino dark matter (DM) candidate within the 19-parameter phenomenological Minimal Supersymmetric Standard Model (pMSSM) in the light of various recent experimental results, especially from the LHC, XENON100, and Planck. We also study the extent of electroweak fine-tuning for such a light neutralino scenario in view of the null results from the searches for supersymmetry so far. Using a Markov Chain Monte Carlo likelihood analysis of the full pMSSM parameter space, we find that a neutralino DM with mass >10 GeV can still in principle satisfy all the existing constraints. Our light neutralino solutions can be broadly divided into two regions: (i) The solutions in the 10 - 35 GeV neutralino mass range are highly fine-tuned and mostly require the existence of a light slepton (below 100 GeV) in order to satisfy the observed DM relic density. We note that such light sleptons are not yet conclusively ruled out by the existing LEP/LHC results, and a dedicated analysis valid for a non-unified gaugino mass spectrum is required to eliminate this low neutralino DM mass regime completely. (ii) The solutions with low fine-tuning are mainly in the 35 - 46 GeV neutralino mass range. However, a major portion of it is already ruled out by the latest XENON100 upper limits on its spin-independent direct detection cross section, and the rest of the allowed points are within the XENON1T projected limit. Thus, we show that the allowed MSSM parameter space for a light neutralino DM below the LEP limit of 46 GeV (strictly applicable to supersymmetric models with gaugino mass unification) could be completely accessible in near future. This might be useful in view of the recent claims for a positive hint of a DM signal in some direct detection experiments.
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http://arxiv.org/abs/1303.5386
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