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Register a new userSearch for astrophysical PeV gamma rays from point sources with Carpet-2
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Early results of the search for E_gamma>1 PeV cosmic photons from point sources with the data of Carpet-2, an air-shower array equipped with a 175 m^2 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 m^2 muon detector), scheduled to start data taking in 2019, for searches of E_gamma>100 TeV photons, are briefly discussed.
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Carpet-2 is an air-shower array at Baksan Valley, Russia, equipped with a large-area (175 m^2) muon detector, which makes it possible to separate primary photons from hadrons. We report the first results of the search for primary photons with energies E_gamma>1 PeV, directionally associated with IceCube high-energy neutrino events, in the data obtained in 3080 days of Carpet-2 live time.
Carpet is an air-shower array at Baksan, Russia, equipped with a large-area muon detector, which makes it possible to separate primary photons from hadrons. We report first results of the search for primary photons with energies E>100 TeV. The experiments ongoing upgrade and future sensitivity are also discussed.
Gamma-ray induced air showers are notable for their lack of muons, compared to hadronic showers. Hence, air shower arrays with large underground muon detectors can select a sample greatly enriched in photon showers by rejecting showers containing muons. IceCube is sensitive to muons with energies above ~500 GeV at the surface, which provides an efficient veto system for hadronic air showers with energies above 1 PeV. One year of data from the 40-string IceCube configuration was used to perform a search for point sources and a Galactic diffuse signal. No sources were found, resulting in a 90% C.L. upper limit on the ratio of gamma rays to cosmic rays of 1.2 x 10^(-3)for the flux coming from the Galactic Plane region (-80 deg < l < -30 deg; -10 deg < b < 5 deg) in the energy range 1.2 - 6.0 PeV. In the same energy range, point source fluxes with E^(-2) spectra have been excluded at a level of (E/TeV)^2 dPhi/dE ~ 10^(-12)-10^(-11) cm^2/s/TeV depending on source declination. The complete IceCube detector will have a better sensitivity, due to the larger detector size, improved reconstruction and vetoing techniques. Preliminary data from the nearly-final IceCube detector configuration has been used to estimate the 5 year sensitivity of the full detector. It is found to be more than an order of magnitude better, allowing the search for PeV extensions of known TeV gamma-ray emitters.
We report on the search of astrophysical gamma rays with energies in the 100 TeV to several PeV range arriving in directional and temporal coincidence with public alerts from HAWC (TeV gamma rays) and IceCube (neutrinos above ~100 TeV). The observations have been performed with the Carpet-2 air-shower detector at the Baksan Neutrino Observatory, working in the photon-friendly mode since 2018. Photon candidate showers are selected by their low muon content. No significant excess of the photon candidates have been observed, and upper limits on gamma-ray fluences associated with the alerts are obtained. For events with good viewing conditions, the Carpet-2 effective area for photons is of the order of the IceCube effective area for neutrinos of the same energy, so the constraints start to probe the production of neutrinos in fast flares of Galactic sources.
We report, for the first time, the long-awaited detection of diffuse gamma rays with energies between 100 TeV and 1 PeV in the Galactic disk. Particularly, all gamma rays above 398 TeV are observed apart from known TeV gamma-ray sources and compatible with expectations from the hadronic emission scenario in which gamma rays originate from the decay of $pi^0$s produced through the interaction of protons with the interstellar medium in the Galaxy. This is strong evidence that cosmic rays are accelerated beyond PeV energies in our Galaxy and spread over the Galactic disk.
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