Search

The mechanisms of origin of ultrahigh-energy gamma radiation are poorly studied. One way to find out is to search for temporal and directional coincidences of high-energy galactic neutrinos with photons of similar energies. The results of such a search could provide indications of the hadronic origin of this radiation. In this paper, we report on the search for photons with energies above 300 TeV in coincidence with high–energy neutrinos. The searches of ultrahigh–energy gammas were carried out at the Carpet–2 EAS array, using three years of data taking.

An experiment for measuring the flux of cosmic gamma rays with energy above 100 TeV is currently being prepared at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. At present the plastic scintillation counters with a total continuous area of 410 m2 are installed in the muon detector (MD) underground tunnels, and they are totally equipped with electronics. Six modules of shower detectors have been already placed on the surface of the MD absorber. In each of them 9 standard plastic scintillation counters are placed with an area of 1 m2 each. These modules are components of the ground surface part of Carpet-3 shower array. The data acquisition system for this array is almost ready. Expected flux limits for cosmic diffuse gamma rays of galactic origin in this work is close to existing experimental limits in the range lower than about 5 PeV, and with improved sensitivity of Carpet-3 one can hope to detect this flux or at least to obtain the best upper limit.

At present an experiment for measuring the flux of cosmic diffuse gamma rays with energy higher than 100 TeV (experiment "Carpet-3") is being prepared at the Baksan Neutrino Observatory of the Institute for Nuclear Research, Russian Academy of Sciences. The preparation of the experiment implies considerable enlargement of the area of both muon detector and surface part of the shower array. At the moment the plastic scintillation counters with a total continuous area of 410 m2 are installed in the muon detector (MD) underground tunnels, and they are totally equipped with electronics. Adjusting of the counters and their electronic circuits is in progress. Six modules of shower detectors (out of twenty planned to be installed) have already been placed on the surface of the MD absorber. A new liquid scintillation detector is developed for modules of the ground –surface part of the array, whose characteristics are presented. It is shown that the "Carpet-3" air shower array will have the best sensitivity to the flux of primary gamma rays with energies in the range 100TeV – 1PeV, being quite competitive in gamma-ray astronomy at such energies.