Neutralino Dark Matter in Focus Point Supersymmetry

TL;DR

The paper analyzes neutralino dark matter within focus point supersymmetry in minimal supergravity, showing that heavy scalar masses do not necessarily overclose the universe because the LSP becomes a mixed gaugino-Higgsino state ($|\mu| \sim M_1, M_2$) and annihilation remains efficient. This yields cosmologically interesting relic densities ($0.025 \lesssim \Omega_χ h^2 \lesssim 0.3$) across a wide range of $m_0$ (up to several tens of TeV) and predicts sizable spin-independent cross sections, $\sigma_P \sim 10^{-6}$–$10^{-7}$ pb, especially at large $\tan\beta$. The results relax cosmological upper bounds on superpartner masses and imply testable signatures in direct-detection experiments and Higgs-sector phenomenology, with $m_h \lesssim 120$ GeV and notable DM detection prospects. Overall, focus point SUSY provides a natural, testable framework where heavy scalars coexist with viable neutralino dark matter and accessible experimental signals.

Abstract

In recent work, it has been argued that multi-TeV masses for scalar superpartners are not unnatural. Indeed, they appear to have significant phenomenological virtues. Here we explore the implications of such `focus point' supersymmetry for the dark matter problem. We find that constraints on relic densities do not place upper bounds on neutralino or scalar masses. We demonstrate that, in the specific context of minimal supergravity, a cosmologically stable mixed gaugino-Higgsino state emerges as an excellent, robust dark matter candidate. We estimate that, over a wide range of the unknown parameters, the spin-independent proton-neutralino cross sections fall in the range accessible to planned search experiments.

Figures (6)

• Figure 1: Contours of constant LSP gaugino fraction $R_{\chi}$ (in percent) in the $(m_0, M_{1/2})$ plane for $A_0=0$, $\mu>0$, and two representative values of $\tan\beta$. The shaded regions are excluded by the requirement that the LSP be neutral (top left) and by the chargino mass limit of 95 GeV (bottom and right). Dashed contours are for the fine tuning parameter $c = 20$, 30, 50, 75 and 100, from below (see text).
• Figure 2: Contours of constant relic density $\Omega_{\chi} h^2$ in the $(m_0, M_{1/2})$ plane for $A_0=0$, $\mu>0$, and two representative values of $\tan\beta$. In the black shaded region, $|2 m_{\chi} - m_h| < 5\text{ GeV}$, and the $h$ pole becomes important. The light shaded regions are as in Fig. \ref{['fig:gfraction']}.
• Figure 3: Contours of proton-$\chi$ cross section $\sigma_P$ in pb in the $(m_0, M_{1/2})$ plane for $A_0=0$, $\mu>0$, and two representative values of $\tan\beta$. The shaded regions are as in Fig. \ref{['fig:gfraction']}.
• Figure 4: Regions of the $(\Omega_{\chi} h^2, \sigma_P)$ plane populated by minimal supergravity models with $m_0 \leq 1\text{ TeV}$ (yellow, light), $1\text{ TeV} < m_0 \leq 1.5\text{ TeV}$ (green, medium), and $1.5\text{ TeV} < m_0$ (blue, dark). The parameters scanned are those given in Fig. \ref{['fig:gfraction']}, subject to the additional naturalness constraint $M_{1/2} \leq 400\text{ GeV}$. We assume neutralino velocity dispersion $\bar{v} = 270\ \text{km/s}$ and local density $\rho_0 = 0.3\ \text{GeV/cm$^3$}$, and $f_{T_s} = 0.14$ (see text).
• Figure 5: Points in minimal supergravity parameter space in the $(m_{\chi}, \sigma_P)$ plane. The parameters scanned, symbols, and assumptions are as in Fig. \ref{['fig:omega_sigma']}.