Beyond standard model particles in the atmospheric flux: a long-lived stau example

TL;DR

This paper explores the production and detection prospects of long-lived staus, a type of supersymmetric particle, in atmospheric cosmic-ray interactions at ultra-high energies, highlighting their potential observability in future detectors.

Contribution

It introduces a detailed calculation of atmospheric stau fluxes from cosmic-ray interactions, considering specific SUSY models and energy distributions, extending previous neutrino flux models.

Findings

Stau fluxes are comparable to prompt atmospheric neutrino fluxes at EeV energies.

Current collider constraints are more restrictive than future detector prospects.

Potential for future ultra-high energy detectors to observe atmospheric staus.

Abstract

We discuss fluxes of long-lived supersymmetric (SUSY) particles produced in the atmosphere from ultra-high energy cosmic-ray interactions with air nuclei. We consider long-lived particle production which proceeds first via the on-shell formation of heavier particles in the SUSY spectrum and then their decays. Specifically, we focus on the production of stau pairs from the decays of squarks produced in the initial cosmic ray-air collision under the purview of gauge-mediated symmetry breaking models that have the stau as the next-to-lightest SUSY particle. The calculation of the resulting stau flux schematically mirrors that of prompt atmospheric neutrino production, however, with the energy scale of initial hadronic collision set to EeV energy scales of the incident cosmic rays rather than the PeV energies where the prompt atmospheric neutrino fluxes dominate over neutrino fluxes from pions and kaons, and with the appropriate stau production cross section. We show the effect of accounting for the energy distribution of the staus relative to the squark energy distributions. We discuss the potential for future ultra-high energy detectors similar in scope to IceCube-Gen2 to detect atmospheric staus via tracks going through the detector volume. Current collider constraints on stau pair production within the SUSY framework considered here are more constraining than those from a detector like IceCube-Gen2 over ten years.