EUSO-SPB2 Cherenkov Telescope: Overview and First Neutrino Constraints

TL;DR

The paper reports on the EUSO-SPB2 Cherenkov telescope's first flight data, setting upper limits on high-energy neutrino fluxes and demonstrating methods for detecting astrophysical neutrinos via Cherenkov signals.

Contribution

It provides the first observational constraints on neutrino fluxes using the EUSO-SPB2 Cherenkov telescope during a balloon flight, and outlines methods for future transient neutrino detection.

Findings

Set upper limits on diffuse astrophysical neutrino flux.

Demonstrated Cherenkov telescope's capability for neutrino detection.

Outlined methodology for transient neutrino source searches.

Abstract

Earth-skimming tau neutrinos with energies above $\sim 10$ PeV can convert to tau leptons that decay in the atmosphere and initiate upward-going extensive air showers that generate optical Cherenkov signals. On a curtailed NASA balloon flight in May 2023, the Cherenkov telescope (CT) on the Extreme Universe Space Observatory on a Super Pressure Balloon 2 (EUSO-SPB2) was launched and had a short flight at $\sim 30$ km altitude. With some time pointing below the Earth's limb, EUSO-SPB2 CT data allow searches for neutrino events that yield optical flashes from the forward-beamed Cherenkov light. We present an overview of the CT and provide upper limits for the diffuse astrophysical neutrino flux from flight data as a proof-of-principle demonstration. We also briefly describe how the methodology is extended to potential transient neutrino point sources.