Speaker
Description
Cosmic-ray antinuclei, in particular antideuterons ($\overline{\rm D}$) and antihelion-3 (${}^3\overline{\rm He}$), are among the most promising messengers for indirect dark matter (DM) searches. Their interest arises from the strong suppression of secondary production in cosmic-ray interactions with the interstellar medium at kinetic energies $K\sim 0.1–1$ GeV/n, where the expected astrophysical background lies one to two orders of magnitude below the flux predicted in many DM scenarios. In this context, recent tentative evidence reported by the Alpha Magnetic Spectrometer (AMS-02) for candidate ${}^3\overline{\rm He}$ events—together with a comparable number of $\overline{\rm D}$—would have profound implications for cosmic-ray physics and dark matter searches if confirmed.
A major theoretical uncertainty in interpreting such signals is the formation of antinuclei, typically modeled through phenomenological coalescence prescriptions. We present a study showing that physically motivated coalescence models can simultaneously reproduce collider measurements in two distinct regimes: (anti)deuteron production in $pp$ collisions measured by ALICE at $\sqrt{s}=0.9-13$ TeV and antideuteron multiplicities in hadronic $Z$ decays measured by ALEPH. These results support an approximately universal coalescence scale and provide a robust framework for predicting antinuclei yields.
Within this framework we also investigate a recently proposed Standard Model mechanism for antihelion-3 production via displaced-vertex decays of $\overline{\Lambda}_b^0$ baryons. Using a dedicated PYTHIA tuning consistent with LEP measurements of $b$-quark fragmentation and with ALICE and ALEPH data on $\overline{\rm D}$ and ${}^3\overline{\rm He}$ production, we derive predictions for antinuclei yields from heavy-flavor decays that are compatible with current LHCb limits. We find that the contribution of beauty-hadron decays to ${}^3\overline{\rm He}$ production is subdominant relative to direct hadronization.
Our results strengthen the theoretical basis for interpreting current and upcoming cosmic-ray antinuclei searches, particularly in light of future measurements by AMS-02 and the upcoming GAPS experiment, which will provide unprecedented sensitivity to low-energy antideuterons from dark matter.