Dark Matter Annihilation Can Produce a Detectable Antihelium Flux through $\bar{\Lambda}_b$ Decays

TL;DR

This paper shows that a standard model process involving $ar{ ext{Lambda}}_b$ decays can greatly increase the expected antihelium flux from dark matter, potentially explaining AMS-02 observations.

Contribution

It introduces a previously neglected decay process that significantly enhances dark matter-induced antihelium production, aligning theoretical predictions with experimental data.

Findings

Displaced-vertex decay of $ar{ ext{Lambda}}_b$ boosts antihelium flux.

This process can triple prompt antihelium production.

It can dominate the high-energy antihelihelium observed by AMS-02.

Abstract

Recent observations by the Alpha Magnetic Spectrometer (AMS-02) have tentatively detected a handful of cosmic-ray antihelium events. Such events have long been considered as smoking-gun evidence for new physics, because astrophysical antihelium production is expected to be negligible. However, the dark-matter-induced antihelium flux is also expected to fall below current sensitivities, particularly in light of existing antiproton constraints. Here, we demonstrate that a previously neglected standard model process -- the production of antihelium through the displaced-vertex decay of $\bar{\Lambda}_b$-baryons -- can significantly boost the dark matter induced antihelium flux. This process can triple the standard prompt-production of antihelium, and more importantly, entirely dominate the production of the high-energy antihelium nuclei reported by AMS-02.