Prospects for Indirect Detection of Neutralino Dark Matter

TL;DR

The paper assesses indirect detection prospects for neutralino dark matter within minimal supergravity, emphasizing the mixed gaugino-Higgsino LSP region made natural by the focus point mechanism. By comparing neutrino, gamma-ray, and positron signals against direct detection and collider searches, it shows that annihilation in this region can yield observable fluxes across multiple channels, while Bino-like LSP scenarios remain largely elusive indirectly. The analysis couples particle-physics parameters (e.g., $m_χ$, $R_χ$, $\sigma v$) with astrophysical inputs (halo models via $\bar{J}$) to forecast sensitivities for upcoming experiments such as AMANDA/NESTOR/ANTARES, MAGIC, GLAST, and AMS-02, and demonstrates strong complementarity among search strategies. The key practical implication is that, within cosmologically favored regions ($0.1\lesssim Ω_χ h^2\lesssim 0.3$), most models should yield some detectable signal before the LHC, motivating coordinated experimental efforts and cross-checks across channels. If no signals are observed prior to the LHC era, significant portions of the natural parameter space would be probed or excluded, underscoring the predictive power of the minimal supergravity framework for dark matter phenomenology.

Abstract

Dark matter candidates arising in models of particle physics incorporating weak scale supersymmetry may produce detectable signals through their annihilation into neutrinos, photons, or positrons. A large number of relevant experiments are planned or underway. The `logically possible' parameter space is unwieldy. By working in the framework of minimal supergravity, we can survey the implications of the experiments for each other, as well as for direct searches, collider searches, low-energy experiments, and naturalness in a transparent fashion. We find that a wide variety of experiments provide interesting probes. Particularly promising signals arise in the mixed gaugino-Higgsino region. This region is favored by low-energy particle physics constraints and arises naturally from minimal supergravity due to the focus point mechanism. Indirect dark matter searches and traditional particle searches are highly complementary. In cosmologically preferred models, if there are charged superpartners with masses below 250 GeV, then some signature of supersymmetry must appear before the LHC begins operation.

Figures (20)

• Figure 1: Contours of constant LSP mass $m_\chi$ in GeV in the $(m_0, M_{1/2})$ plane for $A_0=0$, $\mu>0$, $m_t = 174~\text{GeV}$, and two representative values of $\tan\beta$. The green shaded regions are excluded by the requirement that the LSP be neutral (left) and by the chargino mass limit of 95 GeV (bottom and right). We have also delineated the regions with potentially interesting values of the LSP relic abundance: $0.025\le \Omega_{\chi} h^2 \le 1$ (yellow) and $0.1 \le \Omega_{\chi} h^2 \le 0.3$ (light blue). In the black region, $|2 m_{\chi} - m_h| < 5~\text{GeV}$, and neutralino annihilation is enhanced by a Higgs resonance.
• Figure 2: Contours of constant gaugino fraction $R_{\chi}$ in percent, for the same values of the parameters as in Fig. \ref{['fig:mlsp']}.
• Figure 3: Three leading neutralino annihilation channels.
• Figure 4: Contours of constant $\sigma v$ in pb for (a) $\chi \chi \to WW$ and (b) $\chi \chi \to ZZ$. We fix $A_0=0$, $\mu>0$, $m_t = 174~\text{GeV}$, and $\tan\beta=10$.
• Figure 5: The filling parameter $\sqrt{CA}\, t_{\odot}$ for the Earth. We assume neutralino velocity dispersion $\bar{v} = 270~\text{km}/\text{s}$ and a local density of $\rho_0 = 0.3~\text{GeV}/\text{cm}^3$.