Prospects and blind spots for neutralino dark matter

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 µ. 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 β which sit in a double blind spot for both spin-independent and spin-dependent scattering. Interestingly, these low tan β regions are independently favored in the NMSSM and models of Split Supersymmetry which accommodate a Higgs mass near 125 GeV.1

Blind spots for neutralino dark matter in the NMSSM

“…This result is analogous to the one obtained in [8] for the Higgsino-gaugino LSP in MSSM, but with opposite sign between the two terms in the l.h.s. This difference stems from the fact that both off-diagonal terms, mixing the singlino with two Higgsinos, have the same sign while the two analogous terms, mixing any of the gauginos with the Higgsinos, have opposite signs.…”

“…We find a general formula for the blind spot condition and study it in the most interesting and phenomenologically relevant limiting cases, focusing both on small and large tan β regions. First of all, we identify blind spots analogous to those for a gaugino-Higgsino LSP in the MSSM originating from a vanishing Higgs-neutralino-neutralino coupling [8]. Such blind spots were also found in a general singlet-doublet DM model which mimics NMSSM with a Higgsino-singlino DM with a decoupled scalar singlet and heavy MSSM-like doublet [22] (see also ref.…”

“…We define also some combinations of the above parameters: 8) which encode the information on the scalar sector (mixing, masses and couplings to the nucleons). Using the above definitions we rewrite (3.2) in the form…”

“…In ref. [8] the conditions for MSSM parameters leading to a vanishing Higgs-neutralino-neutralino coupling were found in the limit of decoupled heavy Higgs doublet. Additional blind spots in the MSSM originating from destructive interference between contributions to the scattering amplitude mediated by the 125 GeV Higgs and the heavy Higgs doublet were found in ref.…”

Enhanced Higgs associated production with a top quark pair in the NMSSM with light singlets

“…The LSP scattering cross-section on nucleons for all the benchmarks is below the LUX limits [68] but within the future reach of Xenon1T for direct detection via spin-independent (SI) LSP-nucleon interactions [69]. The compatibility with the LUX constraints is the reason for choosing negative value of M 1 in the benchmarks because µM 1 < 0 allows for some cancellations in the Higgs coupling to LSP which results in smaller SI scattering cross-section [70]. Additional suppression of the SI scattering cross-section may originate from destructive interference between the contributions to the SI scattering amplitude from the Higgs and the light singlet-scalar exchange which are of comparable size if Higgs-singlet mixing is non-negligible as in the present scenario [71].…”