[Paper Review] CoGeNT, DAMA, and Neutralino Dark Matter in the Next-To-Minimal Supersymmetric Standard Model

John F. Gunion, ~Belikov, Alexander V.+1 more|arXiv (Cornell University)|Sep 14, 2010

Particle physics theoretical and experimental studies27 references19 citations

TL;DR

This paper investigates whether the Next-to-Minimal Supersymmetric Standard Model (NMSSM) can explain the CoGeNT and DAMA dark matter signals via a light neutralino (2–12 GeV) with a large spin-independent scattering cross section. Despite satisfying LEP, BaBar, and Tevatron constraints, the NMSSM falls short by a factor of 10–20 in achieving the required cross section under standard assumptions, with only marginal improvement possible via enhanced nucleon s-quark content or higher local dark matter density.

ABSTRACT

We assess the extent to which the NMSSM can allow for light dark matter in the $2\gev\lsim \mcnone\lsim 12\gev$ mass range with correct relic density and large spin-independent direct-detection cross section, $\sigsi$, in the range suggested by \cogent\ and DAMA. For standard assumptions regarding nucleon $s$-quark content and cosmological relic density, $ρ$, we find that the NMSSM falls short by a factor of about 10 to 15 (3 to 5) without (with) significant violation of the current $(g-2)_μ$ constraints.

Motivation & Objective

• To assess whether the NMSSM can produce a light neutralino dark matter candidate (2–12 GeV) with a large spin-independent scattering cross section (σSI) matching CoGeNT and DAMA observations.
• To determine if the NMSSM can simultaneously satisfy cosmological relic density constraints, LEP and BaBar limits on B-physics, and the (g-2)μ anomaly.
• To evaluate whether the NMSSM can achieve the required σSI without violating collider or flavor physics constraints, especially in light of Tevatron data on Higgs and top decays.
• To explore the impact of enhanced s-quark content in nucleons or increased local dark matter density on reducing the required σSI.
• To compare the NMSSM's viability against the more general singlet-extended MSSM model, where larger σSI values are possible under the same constraints.

Proposed method

• Employed a parameter scan of the NMSSM using a combination of theoretical constraints (LEP, BaBar, Tevatron) and phenomenological bounds (relic density, (g-2)μ).
• Used the Feynman diagram involving Higgs exchange (particularly the lightest CP-even Higgs h₁) between the neutralino and nucleon to compute σSI via the effective coupling h₁χ̃₁χ̃₁.
• Applied the relic density calculation using micrOMEGAs to ensure the predicted dark matter density matches the observed ΩCDM ≈ 0.3 GeV/cm³.
• Evaluated the (g-2)μ discrepancy by computing the muon anomalous magnetic moment using one-loop contributions from charginos and neutralinos.
• Incorporated constraints from b→sγ and Bs→μ⁺μ⁻ decays via dedicated flavor physics bounds and BaBar data on rare B decays.
• Assessed the impact of Tevatron data on t→h⁺b and b̄b+Higgs production to constrain the Higgs sector and mixing angles.

Experimental results

Research questions

• RQ1 Can the NMSSM generate a spin-independent neutralino-nucleon scattering cross section large enough to explain the CoGeNT and DAMA signals within the 2–12 GeV mass range?
• RQ2 To what extent do LEP, BaBar, and Tevatron constraints limit the achievable σSI in the NMSSM for light neutralino dark matter?
• RQ3 How does the (g-2)μ anomaly affect the viability of NMSSM scenarios with large σSI, particularly for μeff>0 and μeff<0 cases?
• RQ4 Can enhancements in the nucleon s-quark content or local dark matter density reduce the required σSI to a level achievable in the NMSSM?
• RQ5 How do the results compare to more general singlet-extended models, and what role do additional superpotential or soft-breaking terms play in relaxing constraints?

Key findings

• The NMSSM fails to achieve the required spin-independent cross section (σSI ≈ 1.4–3.5×10⁻⁴ pb) for light neutralino dark matter (2–12 GeV) under standard assumptions about nucleon s-quark content and cosmological relic density.
• For μeff > 0, the maximum achievable σSI is limited to approximately 0.14×10⁻⁴ pb after applying Tevatron constraints, falling short by a factor of 10–20.
• For μeff < 0, σSI reaches up to 0.6×10⁻⁴ pb—within a factor of 3–5 of the required range—but these scenarios predict a muon (g-2)μ value strongly inconsistent with experiment.
• Even with a 50% enhancement in s-quark content and a higher local dark matter density (ρ ≈ 0.4–0.485 GeV/cm³), the required σSI remains at least 5 times larger than the maximum achievable in the NMSSM.
• Tevatron constraints on b̄b+Higgs and t→h⁺b decays are highly relevant and significantly restrict viable parameter space for large σSI.
• The results suggest that only extensions of the NMSSM with additional superpotential or soft-breaking terms can achieve the required σSI while satisfying all constraints, as shown in companion work (Belikov:2010yi).