Abstract
We study the neutralino being the Lightest Supersymmetric Particle (LSP) as a cold Dark Matter (DM) candidate with a mass less than 40 GeV in the framework of the Next-to-Minimal-Supersymmetric-Standard-Model (NMSSM). We find that with the current collider constraints from LEP, the Tevatron and the LHC, there are three types of light DM solutions consistent with the direct/indirect searches as well as the relic abundance considerations: (i) A1, H1-funnels, (ii) stau coannihilation and (iii) sbottom coannihilation. Type-(i) may take place in any theory with a light scalar (or pseudo-scalar) near the LSP pair threshold; while Type-(ii) and (iii) could occur in the framework of Minimal-Supersymmetric-Standard-Model (MSSM) as well. We present a comprehensive study on the properties of these solutions and point out their immediate relevance to the experiments of the underground direct detection such as superCDMS and LUX/LZ, and the astro-physical indirect search such as Fermi-LAT. We also find that the decays of the SM-like Higgs boson may be modified appreciably and the new decay channels to the light SUSY particles may be sizable. The new light CP-even and CP-odd Higgs bosons will decay to a pair of LSPs as well as other observable final states, leading to interesting new Higgs phenomenology at colliders. For the light sfermion searches, the signals would be very challenging to observe at the LHC given the current bounds. However, a high energy and high luminosity lepton collider, such as the ILC, would be able to fully cover these scenarios by searching for events with large missing energy plus charged tracks or displaced vertices.
Highlights
Neutralino sector in the NMSSMIn the NMSSM, the neutralino Dark Matter (DM) candidate is the lightest eigenstate of the neutralino mass matrix [97], which can be written as
It is interesting to understand the viable WIMP mass range under current experimental constraints
We study the neutralino being the Lightest Supersymmetric Particle (LSP) as a cold Dark Matter (DM) candidate with a mass less than 40 GeV in the framework of the Next-to-Minimal-Supersymmetric-Standard-Model (NMSSM)
Summary
In the NMSSM, the neutralino DM candidate is the lightest eigenstate of the neutralino mass matrix [97], which can be written as. The mixing reaches maximum when M1 ∼ 2κ/λμ from simple matrix argument This Bino-Singlino mixing is the only allowed large mixing with light DM candidate due to LEP bounds. A interesting case is the Peccei-Quinn limit [98,99,100,101], when the singlet cubic coupling is small: κ → 0, and both the singlet-like (CP-odd) Higgs boson and the Singlino can be light. The couplings to the SM-like or MSSM-like Higgs bosons are proportional to the BinoHiggsino mixing of the order O(mZsW /μ). The couplings to the SM-like or MSSM-like Higgs bosons are proportional to the SinglinoHiggsino mixing of the order O(λv/μ). For the Singlino-like LSP, the couplings to the SM fermions are more complex as the leading contributions depend on the mixing with the gauginos and Higgsinos
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