Enhanced Cosmic-Ray Antinuclei Fluxes with Dark Matter Annihilation into SUEPs

TL;DR

The paper investigates whether dark matter annihilation into a confining dark sector can enhance heavy antinuclei production in cosmic rays via Soft Unclustered Energy Patterns (SUEPs). By modeling a quasi-conformal dark sector and simulating a large multiplicity of soft dark mesons that promptly decay to SM quarks, the authors show substantial boosts in antideuteron and antihelium-3 yields relative to standard WIMP scenarios, while keeping antiproton fluxes within AMS-02 limits. They employ a full event-by-event coalescence framework, realistic Galactic propagation, and a careful treatment of annihilation cross sections bounded by unitarity and indirect constraints to derive fluxes and event expectations for AMS-02 and GAPS. Their results identify parameter regions where AMS-02 could observe tens to hundreds of antideuteron events and a non-negligible number of antihelium events, providing a potential indirect window into hidden confining dynamics; non-detection would constrain the SUEP parameter space and guide future searches, including collider tests of soft, isotropic dark-showers. The study highlights the interplay between DM model-building, hadronization physics, and cosmic-ray propagation in shaping novel indirect signatures of hidden sectors.

Abstract

Standard-Model (SM) hadronic parton showers initiated by secondary cosmic-ray production or dark matter (DM) annihilations robustly predict very low antinuclei yields and a strong additional suppression for heavier antinuclei. We show that an important exception can arise if DM annihilates into a confining dark sector that produces Soft Unclustered Energy Patterns (SUEPs). The hallmark of SUEPs is the emission of very large multiplicities of soft dark mesons ($π_D$), which can overcome the usual phase-space suppression of antinuclei formation in parton showers, provided that the dark mesons decay promptly into SM quarks, i.e. within a SM hadronization length. We study several benchmark realizations and find that for DM masses $m_{\rm DM}\sim\mathcal{O}(10~\mathrm{TeV})$, dark meson masses $m_{π_D} \sim 400~\mathrm{GeV}$, $π_D$ dominantly decaying to $t\bar t$, and a SUEP temperature $T_{\rm SUEP}\simeq 0.1\,m_{πD}$, DM annihilation into SUEPs can yield tens of antideuterons and a few antihelium--3 events at AMS-02 at kinetic energies of $\mathcal{O}(\mathrm{GeV}$/n) and a few antideuterons and antihelium-3 events in GAPS at energies below 0.5 GeV/n. A future confirmation of an antinuclei signal by the AMS-02 or GAPS experiments could provide hints for hidden confining dynamics and would significantly constrain the relevant SUEP parameters.

Figures (10)

• Figure 1: Scheme of the DM annihilation process into SM antinuclei, with relevant distance scales for the case of producing two boosted SUEPs. Only one SUEP decay is shown for simplicity, but the other SUEP state will decay in the same manner. DM annihilation directly to dark quarks gives rise to a single SUEP, which evolves analogously.
• Figure 2: Value of the ratio $N_{\overline{\rm{D}}}/N_{\overline{p}}$ in the SUEP model as a function of $T_{\rm SUEP}/m_{\pi_D}$ for different decay products. This plot is for $m_{\rm SUEP}=80$ TeV and $m_{\pi_D}=380$ GeV. The numbers on the vertical axis approximately correspond to the enhancement for $N_{\overline{\rm{D}}}/N_{\overline{p}}$ with respect to the standard WIMP case of Eq. \ref{['eq:ratios']} for which $N_{\overline{\rm{D}}}/N_{\overline{p}}\sim 10^{-4}$. Comparable rates are found for hadronic channels with up to $\mathcal{O}(1)$ differences, while a Higgs portal leads to no enhancement due to the long lifetime of an on-shell Higgs.
• Figure 3: Comparison of the propagation function $\mathcal{G}(K/n)$ for $\overline{p}$, $\overline{\mathrm D}$ and ${}^3\overline{\mathrm{He}}$ (see Eq. \ref{['eq:fluxprim']}), for an NFW dark matter density profile.
• Figure 4: Black contours: enhancements of the ratio $N_{\overline{\rm{D}}}/N_{\overline{p}}$ (left panel) and $N_{^3\overline{\rm{He}}}/N_{\overline{p}}$ (right panel) in SUEP decays for a dark meson mass $m_{\pi_D}=380$ GeV and decay portal to $t \bar{t}$, with respect to the standard WIMP expectation for the same antinuclei ratio, i.e. $10^{-4}$ and $10^{-8}$ for $\overline{\rm{D}}$ and $^3\overline{\rm{He}}$ respectively. Red dashed contours show the average multiplicity of dark mesons in a SUEP shower. There are slight fluctuations in the contours in the $^3\overline{\rm{He}}$ enhancement plot which are not present in the antideuteron plot; this is just an artefact of the lower $^3\overline{\rm{He}}$ statistics and interpolating function.
• Figure 5: Comparison of the flux of antimatter from DM annihilation in two scenarios: (1) $m_{\rm DM}=80$ TeV and $T/m_{\pi_D}=0.1$ in the 1 SUEP scenario (blue dot-dashed curves), and (2) $m_{\rm DM}=90$ TeV and $T/m_{\pi_D}=0.1$ in the 2 SUEPs scenario (green dotted curves), together with the GAPS (green dashed) and AMS-02 sensitivities (black dot-dashed) lines. We show the cases of $\overline{p}$ (top panel), $\overline{\mathrm{D}}$ (central panel) and ${}^3\overline{\mathrm{He}}$ (bottom panel). For reference, we also show the standard WIMP expectation for DM annihilating into $b\bar{b}$ with $m_{\rm DM}=50$ GeV and a thermal cross section (red dotted curves), and the secondary $\overline{p}$ production (orange dashed curve).