Recently, the Alpha Magnetic Spectrometer (AMS-02) Collaboration presented tentative evidence for the detection of cosmic antihelion-3 ($\overline{{}^3\mathrm{He}}$) events, alongside a comparable number of antideuterons ($\overline{\mathrm{D}}$). If confirmed, these observations could revolutionize our understanding of cosmic-ray production and propagation and/or serve as compelling indirect evidence for dark matter. Given that the detection of cosmic $\overline{\mathrm{D}}$ is already at the limit of AMS-02 sensitivity, explaining the observation of $\overline{{}^3\mathrm{He}}$ even within the standard coalescence framework poses a significant challenge. It has recently been shown that a previously overlooked mechanism within the Standard Model of particle physics—namely, the production of antihelion via the displaced-vertex decay of ${\overline{\mathrm{\Lambda }}}_b^0$ baryons—could substantially enhance the $\overline{{}^3\mathrm{He}}$ flux arising from dark matter-induced processes. In light of these challenges, we present a tuning of pythia that is consistent with LEP data on the fragmentation function of $b$ quarks into $b$ hadrons—a critical factor for determining the ${\overline{\mathrm{\Lambda }}}_b^0$ multiplicity—and with ALICE and ALEPH data for the $\overline{\mathrm{D}}$ and $\overline{{}^3\mathrm{He}}$ spectra, which we employ to determine our coalescence model. Our refined pythia tuning, in conjunction with our coalescence model, results in a predicted branching ratio for the production of $\overline{{}^3\mathrm{He}}$ from ${\overline{\mathrm{\Lambda }}}_b^0$ decays that is consistent with the recent upper limit measured by LHCb. Furthermore, our prediction indicates that the contribution of $\overline{\mathrm{D}}$ and $\overline{{}^3\mathrm{He}}$ from beauty-hadron decays is negligible relative to the direct production from hadronization.

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• Cosmic rays & astroparticles
• Dark matter
• Particle dark matter