Exploring sub-GeV Dark Matter Physics with Cosmic Ray and Future Telescopes

TL;DR

This work probes sub-GeV dark matter annihilation by leveraging cosmic-ray reacceleration of DM-produced $e^\pm$ and by predicting MeV gamma-ray signals from final-state radiation. It models DM density profiles and CR propagation with the LikeDM framework, and extracts upper limits on $\langle \sigma v\rangle$ from AMS-02 data for $m_\chi$ in the $100\,\mathrm{MeV}$–$1\,\mathrm{GeV}$ range, finding limits around $10^{-28}$–$10^{-27}$ cm$^3$ s$^{-1}$ that are competitive with CMB constraints and stronger than Voyager bounds. It also forecasts gamma-ray fluxes from DM annihilation in the Galactic Center, showing that next-generation MeV telescopes like AMEGO and VLAST could detect or constrain several channels, thereby providing a complementary, independent probe. The paper advocates a multi-messenger approach that combines charged cosmic rays and MeV gamma-ray observations to close the MeV gap and sharpen the search for sub-GeV DM signatures.

Abstract

If sub-GeV Dark matter(DM) annihilates to the charged particles such as $e^+ e^-$, $μ^+ μ^-$, or $π^+ π^-$, it generates an additional source of electrons and positrons in the cosmic ray (CR) population within our Milky Way. During propagation, these secondary electrons and positrons undergo reacceleration processes, boosting their energies to the GeV scale. Observatories like AMS-02 can detect these high-energy particles, enabling constraints on the properties of sub-GeV DM. By analyzing AMS-02 electron and positron data, the 95\% upper limits on the DM annihilation cross-section have been established in the range of $10^{-28}$ to $10^{-27}$ cm$^3\,$s$^{-1}$, corresponding to DM masses ranging from 100 MeV to 1 GeV. Meanwhile, MeV telescopes will provide complementary constraints on DM properties by detecting photon emissions from such annihilation processes. Notably, the sensitivity of future MeV gamma-ray observatories is projected to approach or match the constraints derived from CR data.

Figures (5)

• Figure 1: Our constrains of DM annihilation cross section $\langle\sigma v\rangle$ (black solid lines), compared with existing results from: Voyager data (blue solid lines) and AMS-02 data (red solid line) by M. Boudaud et al. Boudaud:2016mos, X-ray observations (green solid and dotted lines) by M. Cirelli et al. Cirelli:2020bpcCirelli:2023tnx, and CMB analyses (yellow and purple dashed lines) Slatyer:2015jlaLeane:2018kjk. Figure \ref{['fig:Electron']} shows the results for $e^+e^-$, and Fig. \ref{['fig:Muon']} presents those for $\mu^+\mu^-$.
• Figure 2: Our constrains of DM annihilation cross section $\langle\sigma v\rangle$ (black solid lines). The results of 4 electrons are shown in Fig. \ref{['fig:4 electrons']} (compared with results from CMB analyses (purple dashed line) Slatyer:2015jlaLeane:2018kjk), along with those of 4 muons in Fig. \ref{['fig:4 muons']}.
• Figure 3: Our constrains of DM annihilation cross section $\langle\sigma v\rangle$ for pion channel (black solid line), compared with results from X-ray observations (green solid and dotted lines) by M. Cirelli et al. Cirelli:2020bpcCirelli:2023tnx.
• Figure 4: Impact of parameter uncertainties on the limits of DM annihilation cross section $\langle\sigma v\rangle$ in $e^+e^-$ channel. Fig. \ref{['fig:DMprofile']}: Different DM density profile models. Fig. \ref{['fig:prop']}: Different propagation parameters.
• Figure 5: The energy flux of gamma-ray photons resulting from the final state radiation of DM in the Galactic halo across different annihilation channels is depicted. The black dashed line represents the sensitivity of AMEGO AMEGO:2019gnyNegro:2021urm, while the dotted line corresponds to VLAST fanyizhong.