[Paper Review] Light neutralino dark matter in light Higgs scenario related with the CoGeNT and DAMA/LIBRA results

Seodong Shin|arXiv (Cornell University)|Nov 29, 2010

Dark Matter and Cosmic Phenomena30 references3 citations

TL;DR

This paper proposes a light neutralino dark matter scenario in a Beyond-the-MSSM (BMSSM) framework, where a very light CP-even Higgs boson (9–10 GeV) mediates spin-independent scattering, enabling a direct detection cross section of ~10⁻⁴⁰ cm² to explain CoGeNT and DAMA/LIBRA signals. The model achieves the observed relic density via resonant annihilation when the neutralino mass is 5–6 GeV, consistent with WMAP constraints.

ABSTRACT

Recently, the CoGeNT collaboration reported the WIMP candidate signal events exceeding the known backgrounds where the light WIMP with large cross section is supported. Motivated by this issue, we analyze a light neutralino dark matter scenario with a very light CP-even Higgs mediation in the elastic scattering process, which provides the mass and direct detection cross section to explain the CoGeNT result. To be compatible with the result of other experiments such as LEP and B-factories, the light CP-even Higgs is favored to be in 9 to 10 GeV. Such a scenario can be realized in the "Beyond the MSSM" context. The relic abundance consistent with the WMAP result can be obtained when twice of neutralino mass is close to the light Higgs mass via the resonance enhancement of the annihilation cross section. As a result, the neutralino mass is predicted to be at around 5 to 6 GeV.

Motivation & Objective

• To explain the CoGeNT and DAMA/LIBRA direct detection signals of light WIMPs with large spin-independent cross sections (~10⁻⁴⁰ cm²).
• To construct a viable dark matter model with a light neutralino (4–7 GeV) that evades constraints from LEP, B-factories, and XENON100.
• To achieve the observed relic abundance (Ωh² ≈ 0.12) via resonant annihilation through a light Higgs boson in the s-channel.
• To explore the viability of a light CP-even Higgs (9–10 GeV) in the BMSSM framework, avoiding stringent LEP and rare decay constraints.

Proposed method

• Utilizes a light CP-even Higgs boson (mh ≈ 9–10 GeV) as the dominant mediator in neutralino-nucleon elastic scattering, enhancing the spin-independent cross section.
• Applies the BMSSM framework to include small corrections (ε₁, ε₂) to the Higgs sector, allowing a light Higgs while preserving consistency with SM-like Higgs couplings.
• Implements the Higgsstrahlung and associated production constraints from LEP (R_hZ and R_hA) to restrict the parameter space.
• Uses the relic density calculation via s-channel Higgs-mediated annihilation to determine the required neutralino mass, with resonance enhancement near mh/2.
• Solves the neutralino mass eigenstate mixing via the neutralino mixing matrix (N₁₃, N₁₄) and computes the effective coupling g_hχχ using the mixing angle α and β.
• Performs numerical scans over tanβ, ε₁, ε₂, and mh to satisfy both direct detection and cosmological constraints.

Experimental results

Research questions

• RQ1 Can a light neutralino (4–7 GeV) with a spin-independent cross section of ~10⁻⁴⁰ cm² be realized in a phenomenologically viable model compatible with LEP and B-factory constraints?
• RQ2 Is a very light CP-even Higgs (9–10 GeV) compatible with LEP Higgsstrahlung and associated production limits in the BMSSM?
• RQ3 How can the observed relic abundance (Ωh² ≈ 0.12) be achieved for a light neutralino via resonant annihilation?
• RQ4 What are the required parameter values (tanβ, ε₁, ε₂) to simultaneously satisfy direct detection signals and cosmological constraints?

Key findings

• A light CP-even Higgs boson with mass 9–10 GeV enables a spin-independent scattering cross section of ~10⁻⁴⁰ cm², consistent with the CoGeNT and DAMA/LIBRA signals.
• The model remains viable under LEP constraints when sin²(α−β) < 0.01, avoiding excessive Higgsstrahlung and associated production rates.
• The relic abundance is successfully reproduced via s-channel resonant annihilation when the neutralino mass is 5–6 GeV, with mh ≈ 9–10 GeV.
• For tanβ ≈ 3, the required ε₁ ≈ −0.10 to −0.06 and ε₂ ≈ −0.11 to achieve the desired cross section and avoid LEP constraints.
• The model predicts a narrow mass window for the light neutralino: 5–6 GeV, with the upper limit set by the need to avoid overclosure via non-resonant annihilation.
• The scenario is most natural for mh < 10 GeV, as higher masses require fine-tuned parameters and violate R_hA < 0.2 constraints.