Antimatter signals of singlet scalar dark matter

TL;DR

This work investigates indirect detection signals of singlet scalar dark matter via antiprotons and positrons, accounting for Galactic propagation models and possible dark-matter substructure boosts. Using a Green-function approach for antiprotons and a diffusion-based treatment for positrons, the authors map excluded and detectable regions in the (m_S,⟨σv⟩) plane against PAMELA and AMS-02 data, finding antiprotons to be the more promising channel across most of the parameter space. Without boost factors, AMS-02 can probe masses up to about 600 GeV through antiprotons, while positrons mainly test lighter masses; including substructures dramatically enlarges the accessible range, especially for the antiproton channel. The results underscore the value of a multi-maceted indirect-detection strategy, complemented by direct detection and collider data, to constrain or identify the singlet scalar dark matter scenario.

Abstract

We consider the singlet scalar model of dark matter and study the expected antiproton and positron signals from dark matter annihilations. The regions of the viable parameter space of the model that are excluded by present data are determined, as well as those regions that will be probed by the forthcoming experiment AMS-02. In all cases, different propagation models are investigated, and the possible enhancement due to dark matter substructures is analyzed. We find that the antiproton signal is more easily detectable than the positron one over the whole parameter space. For a typical propagation model and without any boost factor, AMS-02 will be able to probe --via antiprotons-- the singlet model of dark matter up to masses of 600 GeV. Antiprotons constitute, therefore, a promising signal to constraint or detect the singlet scalar model.

Figures (8)

• Figure 1: Annihilation branching fractions as a function of the dark matter mass for the singlet model. The higgs mass was set to $120~\mathrm{GeV}$ while the value of $\lambda$ was obtained by imposing the dark matter constraint.
• Figure 2: Regions of the parameter space that are excluded by the recent antiproton data from the PAMELA experiment. The area above the MIN, MED, and MAX lines is excluded for the given propagation model. The solid (black) line shows the viable parameter space of the singlet scalar model of dark matter.
• Figure 3: Regions of the parameter space that are within the sensitivity of the AMS-2 experiment. The area above the MIN, MED, and MAX lines is detectable by AMS-02. The solid (black) line shows the prediction of the singlet model. Notice that for MED and MAX, essentially the whole parameter space is detectable.
• Figure 4: Regions excluded by the antiproton data from PAMELA including the possible effect of substructures in the DM halo. From top to bottom the figures correspond to the MIN, MED, and MAX propagation models. The solid (black) line shows the prediction of the singlet model. The area above the lines is excluded for the corresponding parameter values.
• Figure 5: Detectable regions at AMS-02 including the possible effect of substructures. From top to bottom the figures correspond to the MIN, MED, and MAX propagation models. The solid (black) line shows the prediction of the singlet model. The area above the lines is detectable for the corresponding parameter values.