Abstract
Early results of the search for Eγ > 1 PeV cosmic photons from point sources with the data of Carpet–2, an air-shower array equipped with a 175 m2 muon detector, are presented. They include 95% CL upper limits on PeV photon fluxes from stacked directions of high-energy IceCube neutrino events and from four predefined sources, Crab, Cyg X-3, Mrk 421 and Mrk 501. An insignificant excess of events from Mrk 421 will be further monitored. Prospects of the use of the upgraded installation, Carpet–3 (410 m2 muon detector), scheduled to start data taking in 2019, for searches of Eγ > 100 TeV photons, are briefly discussed.
Highlights
The data on astrophysical photons with energies above ∼ 0.1 PeV are presently very scarce, though their observation or non-observation is very important for understanding many astrophysical and particle-physics phenomena
Any observation of an air shower induced by a primary gamma ray of that high energy would strongly constrain hypothetical models with tiny, though presently not excluded, deviations from the Lorentz invariance [4]
These results are based on the data obtained with the 175 m2 muon detector, shower cores in the central unit of 200 m2 area and the trigger of nμ > 1
Summary
The data on astrophysical photons with energies above ∼ 0.1 PeV are presently very scarce (no significant detection so far), though their observation or non-observation is very important for understanding many astrophysical and particle-physics phenomena. The cosmic gamma rays of Eγ ∼ (0.1 − 10) PeV produce electron-positron pairs on the Cosmic Microwave Background [1]. This process limits their mean free path to the size of the Galaxy. If no new physics is assumed, every single detected astrophysical photon of this energy is certainly Galactic. This makes PeV photons very useful in constraining unknown astrophysical sources, notably those of high-energy neutrinos detected by IceCube While future large-scale instruments like TAIGA [7] or LHAASO [8] aim at this energy band, this work presents early results of the search for cosmic photons with energies Eγ 1 PeV with the Carpet–2 extensive air shower array at the Baksan Neutrino Observatory of INR RAS
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