Zooming in on light relic neutralinos by direct detection and measurements of galactic antimatter

TL;DR

This work addresses whether light neutralinos can account for the DAMA/NaI annual modulation when channeling is included, and whether these candidates are compatible with indirect detection via galactic antimatter. It combines an effMSSM framework with non-unified gaugino masses to produce light neutralinos, analyzes the DAMA region under a cored isothermal halo, and computes antiproton and antideuteron fluxes using a two-zone diffusion model constrained by cosmic-ray data. The results show that $m_\chi$ in the range $\sim 7-30$ GeV can fit the DAMA region and remain consistent with current antiproton data for plausible diffusion parameters, while antideuteron measurements promise strong tests of these scenarios. Together, the direct and indirect-detection analyses yield a coherent, testable picture linking DAMA hints to specific light neutralino populations, guiding future experiments (PAMELA/AMS/GAPS) to probe these candidates.

Abstract

The DAMA Collaboration has recently analyzed its data of the extensive WIMP direct search (DAMA/NaI) which detected an annual modulation, by taking into account the channelling effect which occurs when an ion traverses a detector with a crystalline structure. Among possible implications, this Collaboration has considered the case of a coherent WIMP-nucleus interaction and then derived the form of the annual modulation region in the plane of the WIMP-nucleon cross section versus the WIMP mass, using a specific modelling for the channelling effect. In the present paper we first show that light neutralinos fit the annual modulation region also when channelling is taken into account. To discuss the connection with indirect signals consisting in galactic antimatter, in our analysis we pick up a specific galactic model, the cored isothermal-sphere. In this scheme we determine the sets of supersymmetric models selected by the annual modulation regions and then prove that these sets are compatible with the available data on galactic antiprotons. We comment on implications when other galactic distribution functions are employed. Finally, we show that future measurements on galactic antiprotons and antideuterons will be able to shed further light on the populations of light neutralinos singled out by the annual modulation data.

Figures (5)

• Figure 1: WIMP--nucleon scattering cross-section as a function of the WIMP mass. The solid (dashed) line denotes the annual modulation region derived by the DAMA Collaboration with (without) the inclusion of the channeling effect. The two regions contain points where the likelihood- function values differ more than 4$\sigma$ from the null hypothesis (absence of modulation). These regions are obtained by varying the WIMP galactic distribution function (DF) over the set considered in Ref. bcfs and by taking into account other uncertainties of different origins damalast. The scatter plot represents supersymmetric configurations calculated with the supersymmetric model summarized in the Appendix. The (red) crosses denote configurations with a neutralino relic abundance which matches the WMAP cold dark matter amount ($0.092 \leq \Omega_{\chi} h^2 \leq 0.124$), while the (blue) dots refer to configurations where the neutralino is subdominant ($\Omega_{\chi} h^2 < 0.092$).
• Figure 2: WIMP--nucleon scattering cross-section as a function of the WIMP mass. The solid contours denote the DAMA/NaI annual modulation regions for a cored isothermal halo, derived by including the channeling effect with the model explained in Ref. damalast. The different panels refer to different galactic halo--model parameters, according to the analysis of Ref. bcfs: $v_{0}$ is the local rotational velocity, $\rho_{0}$ is the local dark matter density. The scatter plot shows the configurations for neutralino--nucleon scattering in gaugino non--universal supersymmetric models. The (red) crosses denote configurations with a neutralino relic abundance which matches the WMAP cold dark matter amount ($0.092 \leq \Omega_{\chi} h^2 \leq 0.124$), while the (blue) dots refer to configurations where the neutralino is subdominant ($\Omega_{\chi} h^2 < 0.092$).
• Figure 3: Antiproton flux at $\bar{p}$ kinetic energy $T_{\bar{p}}=0.23$ GeV, as a function of the WIMP mass and for a cored isothermal halo. Each raw correspond to a different set of cosmic--rays propagation parameters: the upper, median and lower rows refer to the set which provides the maximal, median and minimal antiproton flux, according to the analysis of Ref. pbar. The light gray points denote configurations with a neutralino--nucleon scattering cross section outside the corresponding DAMA/NaI allowed region. The bold (colored) points refer to configurations compatible with the DAMA/NaI regions. These last points are further differentiated as follows: (red) crosses denote configurations with a neutralino relic abundance which matches the WMAP cold dark matter amount ($0.092 \leq \Omega_{\chi} h^2 \leq 0.124$), while (blue) dots refer to configurations where the neutralino is subdominant ($\Omega_{\chi} h^2 < 0.092$). The solid horizontal line shows the maximal allowable amount of antiprotons in the BESS data bess over the secondary component; the dashed and dotted lines denote estimates of the PAMELA and AMS sensitivities to exotic antiprotons for 3 years missions, respectively.
• Figure 4: Areas of compatibility between the annual modulation regions of Fig. \ref{['fig:01']} and the antiproton data for a neutralino of mass of 20 GeV, plotted in the parameter space defined by the height of the diffusive halo $L$ and the rigidity--dependence parameter $\delta$ of the diffusion coefficient of Eq. (\ref{['iso']}). The galactic halo model is a cored-isothermal sphere. The dots, (red) squares and (blue) circles refer to: $v_0 = 170$ km sec$^{-1}$, $\rho_0 = \rho_0^{\rm min} = 0.20$ GeV cm$^{-3}$, $v_0 = 220$ km sec$^{-1}$, $\rho_0 = \rho_0^{\rm min} = 0.34$ GeV cm$^{-3}$, and $v_0 = 170$ km sec$^{-1}$, $\rho_0 = \rho_0^{\rm max} = 0.42$ GeV cm$^{-3}$, respectively. Each set of points shows the region in the $L$--$\delta$ plane which fits at 99.5% C.L. the antiproton data of BESS bess.
• Figure 5: Antideuteron flux at $\bar{D}$ kinetic energy $T_{\bar{D}}=0.23$ GeV/n, as a function of the WIMP mass and for a cored isothermal halo. Notations are as in Fig. \ref{['fig:02']}, except for the horizontal lines, which here refer to estimated sensitivities to antideuterons of the GAPS (dashed) and AMS (dotted) detectors.