Indirect detection of light neutralino dark matter in the NMSSM

TL;DR

This work develops and applies a comprehensive NMSSM framework to indirect dark matter detection, deriving the first full one-loop amplitudes for neutralino annihilation to $\gamma\gamma$ and $gg$ and showing how a light CP-odd Higgs $a_1$ enhances these radiative channels. It analyzes a broad NMSSM parameter space with $m_{\tilde{\chi}_1^0} \lesssim 100\,{\rm GeV}$, predicting enhanced Earth-based neutrino fluxes, sizable antimatter signatures in the Galactic halo, and potentially observable monochromatic gamma-ray lines in optimistic halo scenarios. The paper also investigates solar-physics bounds from neutralino energy transport, finding most models have negligible impact but some light-bino scenarios could be testable with improved solar modeling. Overall, it identifies distinct NMSSM indirect-detection fingerprints—especially via $\chi\chi \to \gamma\gamma$ and halo antimatter signals—that motivate targeted searches with upcoming detectors (ANTARES, PAMELA/AMS-02, GAPS, GLAST). The results underscore the NMSSM’s rich phenomenology and its potential to reveal dark matter through multiple, complementary channels.

Abstract

We explore the prospects for indirect detection of neutralino dark matter in supersymmetric models with an extended Higgs sector (NMSSM). We compute, for the first time, one-loop amplitudes for NMSSM neutralino pair annihilation into two photons and two gluons, and point out that extra diagrams (with respect to the MSSM), featuring a potentially light CP-odd Higgs boson exchange, can strongly enhance these radiative modes. Expected signals in neutrino telescopes due to the annihilation of relic neutralinos in the Sun and in the Earth are evaluated, as well as the prospects of detection of a neutralino annihilation signal in space-based gamma-ray, antiproton and positron search experiments, and at low-energy antideuteron searches. We find that in the low mass regime the signals from capture in the Earth are enhanced compared to the MSSM, and that NMSSM neutralinos have a remote possibility of affecting solar dynamics. Also, antimatter experiments are an excellent probe of galactic NMSSM dark matter. We also find enhanced two photon decay modes that make the possibility of the detection of a monochromatic gamma-ray line within the NMSSM more promising than in the MSSM.

Figures (12)

• Figure 1: The allowed region of $(\lambda-\kappa)$ parameter space (upper-left); the $m_{\widetilde{\chi}_1^0}$ vs. $m_{a_1}$ plane (upper-right)-- the decay $a_1 \rightarrow {\widetilde{\chi}_1^0} {\widetilde{\chi}_1^0}$ is allowed for those models below the line; the $(\tan \beta-\lambda)$ viable parameter space (lower-left); $A_\kappa$ as a function of the lightest CP-odd Higgs mass (lower-right)
• Figure 2: Equilibrium times between capture and annihilation in the Earth (left) and the Sun (right). Models below the line marking the age of the solar system have attained equilibrium and will have an $\Gamma_{ann}\sim C/2$
• Figure 3: Integrated muon fluxes above $E_\mu \ge 1 {\rm GeV}$ from the Earth (left) and the Sun (right). The horizontal line displays the MACRO bound Ambrosio:1998qj.
• Figure 4: Knudsen number, Eq. (\ref{['knudsen']}), at a distance $r_\chi$
• Figure 5: Neutralino luminosity in units of ${\cal L}_\odot$.