A Statistical Analysis of Supersymmetric Dark Matter in the MSSM after WMAP

TL;DR

This paper tackles neutralino dark matter in the general, flavor-diagonal MSSM under the WMAP constraint, using a comprehensive random scan of 20 soft-breaking parameters to map viable models without assuming mSUGRA relations. It shows that most viable scenarios feature higgsino- or wino-like LSPs with relic densities below the WMAP bound, while models with relic density in the WMAP range are dominated by higgsinos, with binos requiring coannihilations or resonances for viability. The authors analyze direct and indirect detection prospects with self-consistent halo models and introduce visibility ratios to compare strategies, finding that current data barely constrain the parameter space but future direct detection could probe a significant fraction of viable models; indirect detection remains highly halo- and relic-density dependent. The work highlights that relic-density enhancement mechanisms are crucial for optimistic indirect-detection prospects and suggests that mSUGRA is not a fully representative benchmark for SUSY dark matter in the general MSSM, with important implications for experimental search planning.

Abstract

We study supersymmetric dark matter in the general flavor diagonal MSSM by means of an extensive random scan of its parameter space. We find that, in contrast with the standard mSUGRA lore, the large majority of viable models features either a higgsino or a wino-like lightest neutralino, and yields a relic abundance well below the WMAP bound. Among the models with neutralino relic density within the WMAP range, higgsino-like neutralinos are still dominant, though a sizeable fraction of binos is also present. In this latter case, relic density suppression mechanisms are shown to be essential in order to obtain the correct neutralino abundance. We then carry out a statistical analysis and a general discussion of neutralino dark matter direct detection and of indirect neutralino detection at neutrino telescopes and at antimatter search experiments. We point out that current data exclude only a marginal portion of the viable parameter space, and that models whose thermal relic abundance lies in the WMAP range will be significantly probed only at future direct detection experiments. Finally, we emphasize the importance of relic density enhancement mechanisms for indirect detection perspectives, in particular at future antimatter search experiments.

Figures (25)

• Figure 1: Effectiveness of the different constraints imposed on supersymmetric models.
• Figure 2: (a): $BF(b\rightarrow s\gamma)$ in units of $10^{-4}$. (b): The Higgs boson mass, in GeV. An upper bound $m_h\leq 132$ emerges from our scan.
• Figure 3: The supersymmetric contribution to the anomalous magnetic moment of the muon ($a_\mu=(g-2)_\mu/2$) in units of $10^{-10}$.
• Figure 4: The neutralino relic density as a function of $m_\chi$ for a bino-, a wino- and a higgsino-like neutralino. All other superparticles are assumed to have a mass much larger than $m_\chi$: $m_{susy}\approx a\cdot m_{\chi}$, with $a=3,5,10$.
• Figure 5: Histograms of the neutralino relic density. The first panel shows the statistical distribution of the neutralino relic density for all models. In the other panels, the relic density of a bino-, a wino- and a higgsino-like neutralino are shown. The gray vertical band corresponds to the WMAP range.