# First Detection of Photons with Energy Beyond 100 TeV from an Astrophysical Source

## TL;DR

This paper reports the first detection of photons with energies exceeding 100 TeV from an astrophysical source, specifically the Crab Nebula, using the Tibet air shower array with muon detectors, achieving high background suppression and significant statistical confidence.

## Contribution

The study introduces a novel detection of ultra-high-energy photons from an astrophysical source, demonstrating the effectiveness of muon number criteria for background suppression at energies above 100 TeV.

## Key findings

- Detected 24 photon-like events with E>100 TeV from Crab Nebula
- Achieved 99.92% background suppression using muon number criteria
- Observed a 5.6 sigma statistical significance for the photon detection

## Abstract

We report on the highest energy photons from the Crab Nebula observed by the Tibet air shower array with the underground water-Cherenkov-type muon detector array. Based on the criterion of muon number measured in an air shower, we successfully suppress 99.92% of the cosmic-ray background events with energies $E>100$ TeV. As a result, we observed 24 photon-like events with $E>100$ TeV against 5.5 background events, which corresponds to 5.6$\sigma$ statistical significance. This is the first detection of photons with $E>100$ TeV from an astrophysical source.