Abstract
Using a simplified model framework, we assess observational limits and discovery prospects for neutralino dark matter, taken here to be a general admixture of bino, wino, and Higgsino. Experimental constraints can be weakened or even nullified in regions of parameter space near 1) purity limits, where the dark matter is mostly bino, wino, or Higgsino, or 2) blind spots, where the relevant couplings of dark matter to the $Z$ or Higgs bosons vanish identically. We analytically identify all blind spots relevant to spin-independent and spin-dependent scattering and show that they arise for diverse choices of relative signs among $M_1$, $M_2$, and $\mu$. At present, XENON100 and IceCube still permit large swaths of viable parameter space, including the well-tempered neutralino. On the other hand, upcoming experiments should have sufficient reach to discover dark matter in much of the remaining parameter space. Our results are broadly applicable, and account for a variety of thermal and non-thermal cosmological histories, including scenarios in which neutralinos are just a component of the observed dark matter today. Because this analysis is indifferent to the fine-tuning of electroweak symmetry breaking, our findings also hold for many models of neutralino dark matter in the MSSM, NMSSM, and Split Supersymmetry. We have identified parameter regions at low $\tan \beta$ which sit in a double blind spot for both spin-independent and spin-dependent scattering. Interestingly, these low $\tan \beta$ regions are independently favored in the NMSSM and models of Split Supersymmetry which accommodate a Higgs mass near 125 GeV.
Highlights
Colored superpartners decaying to missing energy — direct limits on the bino, wino, and Higgsino still remain weak
Our results are broadly applicable, and account for a variety of thermal and non-thermal cosmological histories, including scenarios in which neutralinos are just a component of the observed dark matter today. Because this analysis is indifferent to the fine-tuning of electroweak symmetry breaking, our findings hold for many models of neutralino dark matter in the minimal supersymmetric standard model (MSSM), next-to-minimal supersymmetric standard model (NMSSM), and Split Supersymmetry
In this paper we have presented a systematic analysis of the current limits and projected reach for χ ∼ (B, W, h) neutralino DM using simplified models
Summary
We enumerate the experiments relevant to neutralino DM and broadly outline their status and future reach. The SI scattering of DM with nucleons is highly constrained by null results from direct detection experiments. As shown to the left of figure 1, XENON100 provides the current leading experimental limit on SI scattering; their latest limit uses an exposure of 0.02 ton × years. The projection in figure 1 shows the estimated limit with an exposure of 2.2 ton × years. LUX [4] — a direct detection experiment of similar design but with a Xe target volume of 350 kg — is slated for operation in ∼ 2013, and has a projected reach between that of XENON100 and XENON1T. The strongest constraint comes from a combined Fermi analysis of 10 satellite galaxies using 2 years of data [30], a recent re-analysis weakens this limit by a factor of ∼ 2 compared to the published result [31]. We will not consider the LHC limits further in this paper because we focus on DM heavier than 100 GeV, where these limits are not relevant
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