Abstract
Given the recent constraints from the dark matter (DM) direct detections, we examine a light GeV-scale (2–30 GeV) neutralino DM in the alignment limit of the Minimal Supersymmetric Standard Model (MSSM). In this limit without decoupling, the heavy CP-even scalar H plays the role of the Standard Model (SM) Higgs boson while the other scalar h can be rather light so that the DM can annihilate through the h resonance or into a pair of h to achieve the observed relic density. With the current collider and cosmological constraints, we find that such a light neutralino DM above 6 GeV can be excluded by the XENON-1T (2017) limits while the survivied parameter space below 6 GeV can be fully tested by the future germanium-based light dark matter detections (such as CDEX), by the Higgs coupling precison measurements or by the production process e+e−→hA at an electron–positron collider (Higgs factory).
Highlights
The existence of cold dark matter (CDM) has been confirmed by many astrophysical experiments
This conclusion may not be valid in the alignment limit with H being the 125 GeV Higgs boson, which motivates our upper value of M1
We examined a light GeV-scale neutralino dark matter (2-30 GeV) in the Minimal Supersymmetric Standard Model (MSSM)
Summary
The existence of cold dark matter (CDM) has been confirmed by many astrophysical experiments. With the LHC data, the precision electroweak data and flavour measurements as well as the dark matter detection limits, the typical WIMP mass range has been largely excluded, albeit some blind spots in direct detections are still remained due to some accidental cancellation in the couplings of Higgs/Z boson with the neutralino DM. Due to accidental cancellation effects in the alignment limit without decoupling [7,8,9,10,11], the heavier CP-even scalar (H) can serve as the observed 125 GeV Higgs boson while the other scalar h can be very light.
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