Interpreting the recent results on direct search for dark matter particles in terms of relic neutralino

TL;DR

The paper investigates whether DAMA's annual modulation can be explained by relic neutralinos within an effective MSSM, without gaugino-mass unification, by performing a comprehensive parameter scan that includes hadronic uncertainties in neutralino-quark couplings, a range of galactic halo distribution functions, and constraints from complementary data. It shows that DAMA-compatible regions exist for $m_{\chi} \lesssim 100$ GeV, particularly when channeling is considered, and that many such neutralino configurations survive current antiproton bounds while predicting detectable antideuteron signals for upcoming experiments. The study also connects direct-detection interpretations to collider prospects, arguing that LHC measurements could confirm or challenge the light neutralino scenario, thus providing a concrete cross-check across astrophysical and collider observations. Overall, the results illustrate that light neutralinos remain viable dark matter candidates compatible with DAMA and motivate targeted searches in cosmic antimatter and at the LHC.

Abstract

The most recent results from direct searches for dark matter particles in the galactic halo are examined in terms of an effective Minimal Supersymmetric extension of the Standard Model at the electroweak scale without gaugino masses unification. We show that the annual modulation effect at 8.2 $σ$ C.L. recently presented by the DAMA Collaboration, as the result of a combined analysis of the DAMA/NaI and the DAMA/LIBRA experiments for a total exposure of 0.82 ton yr, fits remarkably well with what expected for relic neutralinos for a wide variety of WIMP distribution functions. Bounds derivable from other measurements of direct searches for dark matter particles are analyzed. We stress the role played by the uncertainties affecting the neutralino--quark couplings arising from the involved hadronic quantities. We also examine how present data on cosmic antiprotons can help in constraining the neutralino configurations selected by the DAMA effect, in connection with the values of the astrophysical parameters. Perspectives for measurement of antideuterons possibly produced in the galactic halo by self--annihilation of neutralinos belonging to the DAMA configurations are examined. Finally, we discuss how findings at LHC would impact on these issues.

Figures (10)

• Figure 1: $\xi \sigma_{\rm scalar}^{(\rm nucleon)}$ as a function of the WIMP mass. The region covered by a (red) slant hatching denotes the DAMA annual modulation region, under the hypothesis that the effect is due to a WIMP with a coherent interaction with nuclei and without including the channeling effect. This region represents the domain where the likelihood-function values differ more than 6.5 $\sigma$ from the null hypothesis (absence of modulation). It has been derived by the DAMA Collaboration by varying the WIMP galactic distribution function over the set considered in Ref.bcfs and by taking into account other uncertainties of different origins note1. The scatter plot represents supersymmetric configurations calculated with the model summarized in Sect. \ref{['sec:susy']}, at the fixed representative set of values for the hadronic quantities characterized by: $g_{u,ref}$ = 123 MeV, $g_{d,ref}$ = 290 MeV. The (red) crosses denote configurations with a neutralino relic abundance which matches the WMAP cold dark matter amount ($0.098 \leq \Omega_{\chi} h^2 \leq 0.122$), while the (blue) dots refer to configurations where the neutralino is subdominant ($\Omega_{\chi} h^2 < 0.098$). The (blue) uniformly--shaded region represents the extension of the scatter plot upwards and downwards, when the hadronic uncertainties reported in Eq. (\ref{['eq:q']}) are included (see text).
• Figure 2: $\xi \sigma_{\rm scalar}^{(\rm nucleon)}$ as a function of the WIMP mass. The region covered by a (red) slant hatching denotes the DAMA annual modulation region, under the hypothesis that the effect is due to a WIMP with a coherent interaction with nuclei and including the channeling effect. All other prerequisites of this region are as in Fig. \ref{['fig:01']}. The scatter plot and the (blue) uniformly--shaded region are as in Fig. \ref{['fig:01']}.
• Figure 3: $\xi \sigma_{\rm scalar}^{(\rm nucleon)}$ as a function of the WIMP mass. The region covered by a (red) slant hatching denotes the DAMA annual modulation region, under the hypothesis that the effect is due to a WIMP with a coherent interaction with nuclei and without including the channeling effect. This region represents the domain where the likelihood-function values differ more than 6.5 $\sigma$ from the null hypothesis (absence of modulation). It has been derived by the DAMA Collaboration by assuming that the WIMP distribution function is given by the cored isothermal sphere (denoted as Evans logarithmic model, or A1 model, in Ref. bcfs) and using the parameters of set A of Sect. 7.2 of the first paper of Ref. dama/nai. The scatter plot and the (blue) uniformly--shaded region are as in Fig. \ref{['fig:01']}.
• Figure 4: $\xi \sigma_{\rm scalar}^{(\rm nucleon)}$ as a function of the WIMP mass. The region covered by a (red) slant hatching denotes the DAMA annual modulation region, under the hypothesis that the effect is due to a WIMP with a coherent interaction with nuclei and including the channeling effect. All other prerequisites of this region are as in Fig. \ref{['fig:03']}. The scatter plot and the (blue) uniformly--shaded region are as in Fig. \ref{['fig:01']}.
• Figure 5: The solid lines show the upper limit on the quantity $\xi \sigma_{\rm scalar}^{(\rm nucleon)}$ as a function of the WIMP mass $m_\chi$ for the CDMS detector cdms and for $v_{\rm esc}=650$ km sec$^{-1}$. The (red) median line refers to the standard isothermal sphere with $v_0 =220$ km sec$^{-1}$ and $\rho_0 =0.3 ~{\rm GeV\,cm^{-3}}$ (model A0 of Ref. bcfs). The (black) upper and lower curves refer to model B1 with $v_0 =170$ km sec$^{-1}$ (upper solid line) and model C3 with $v_0 =270$ km sec$^{-1}$ (lower solid line). The short--dashed line refers to model C3 with maximal counter--rotation of the galactic halo. The long--dashed lines show the upper limits for CDMS in the case of a lower escape velocity $v_{\rm esc}=450$ km sec$^{-1}$: the upper line refers to model A1, the lower one to model C3. For model B1, the limit coincides with the corresponding solid line. The scatter plot and the (blue) uniformly--shaded region are as in Fig. \ref{['fig:01']}. Other specifications in the text.