EUSO-SPB2 Cosmic Ray Searches and Observations (2509.05147v1)

Abstract: The Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) flew in May of 2023, marking an important step towards the observation of ultra-high-energy cosmic rays (UHECR) and neutrino-induced showers from space. The ultimate goal of this endeavor is to complement ground-based detectors and achieve unprecedented exposure and nearly uniform full-sky coverage at the highest energies, thereby enabling charged particle astronomy and enriching the multi-messenger approach to high-energy astrophysics and astroparticle physics. As a pathfinder to the POEMMA mission (Probe Of Extreme Multi-Messenger Astrophysics), EUSO-SPB2 flew two distinct cameras at the focus of two Schmidt telescopes, one made of multi-anode photomultiplier tubes (MAPMTs), looking towards the nadir for fluorescence light detection, the other made of Silicon photomultipliers (SiPMs), looking towards the limb of the Earth for direct Cherenkov light detection. The flight was terminated prematurely due to a failure in the balloon, and thus no showers were detected in the fluorescence mode. However, several lower-energy (PeV scale) cosmic-ray events were observed in the Cherenkov channel. The data collected by both telescopes also confirmed the pertinence and maturity of the technology. We will report on the mission's cosmic ray results, and lessons learned for future balloon and satellite missions, notably the POEMMA Balloon with Radio (PBR), currently under development.