Upper limits on the isotropic diffuse flux of cosmic PeV photons from Carpet-2 observations

TL;DR

This paper reports new upper limits on the isotropic diffuse PeV gamma-ray flux using Carpet-2 data, providing constraints for astrophysical models and searches for new physics in high-energy cosmic phenomena.

Contribution

It introduces a novel statistical method based on muon-number distribution shape to set upper limits on PeV gamma-ray flux from extensive air-shower data.

Findings

Established new upper limits on PeV gamma-ray flux.

Demonstrated effectiveness of the muon-number shape analysis method.

Provided data constraints relevant for multimessenger astrophysics.

Abstract

Isotropic diffuse gamma-ray flux in the PeV energy band is an important tool for multimessenger tests of models of the origin of high-energy astrophysical neutrinos and for new-physics searches. So far, this flux has not yet been observed. Carpet-2 is an air-shower experiment capable of detecting astrophysical gamma rays with energies above 0.1 PeV. Here we report the upper limits on the isotropic gamma-ray flux from Carpet-2 data obtained in 1999-2011 and 2018-2022. These results, obtained with the new statistical method based on the shape of the muon-number distribution, summarize Carpet-2 observations as the upgraded installation, Carpet-3, starts its operation.