Abstract
We report on the development and operation of an imaging atmospheric Cherenkov telescope (IACT) designed to detect extensive air showers (EAS) from Earth-emergent tau neutrinos and cosmic rays from sub-orbital altitudes. The telescope flew on the Extreme Universe Space Observatory Super Pressure Balloon 2 (EUSO-SPB2) on May 13th and 14th, 2023. Successfully operating an IACT for the first time at such altitudes was a crucial step towards opening a new window in high-energy astrophysics, the very-high energy (VHE: >1 PeV) neutrino band. VHE neutrinos probe hadronic processes in cosmic accelerators, including those producing Ultra-High Energy Cosmic Rays (UHECRs) while providing a measure of the composition of UHECRs and exploring neutrino/particle physics at the highest energies. During our short flight, the telescope was pointed above and below the Earth's limb and at different azimuth angles, assessing the telescope operation and exploring the ambient background light levels while detecting EAS images initiated by horizontal cosmic rays in the atmosphere for the first time. In this presentation, the performance of our telescope, recorded air-shower images, and preliminary results searching for Earth-skimming neutrinos will be discussed.
* The authors acknowledge the support by NASA awards 11-APRA-0058, 16-APROBES16-0023, 17-APRA17-0066, NNX17AJ82G, NNX13AH54G, 80NSSC18K0246, 80NSSC18K0473, 80NSSC19K0626, 80NSSC18K0464, 80NSSC22K1488, 80NSSC19K0627 and 80NSSC22K0426, the French space agency CNES, National Science Centre in Poland grant n. 2017/27/B/ST9/02162, and by ASI-INFN agreement n. 2021-8-HH.0 and its amendments. This research used resources of the US National Energy Research Scientific Computing Center (NERSC), the DOE Science User Facility operated under Contract No. DE-AC02-05CH11231. We acknowledge the NASA BPO and CSBF staffs for their extensive support. We also acknowledge the invaluable contributions of the administrative and technical staffs at our home institutions.
