Speaker
Description
Cosmic rays are thought to be accelerated up to a few PeV by the most powerful sources, the so-called “PeVatron” in the Galaxy. On the other hand, gamma rays beyond 100 TeV are expected by the neutral pion decays caused by the interaction of these cosmic rays with the interstellar medium. Therefore, the gamma-ray observation is key to unveiling a long-standing mystery, the origin and the propagation of very-high-energy cosmic rays in the Galaxy, because gamma rays go straight unaffected by the magnetic field, pointing back to the sources.The Tibet air shower (AS) array and the underground water-Cherenkov-type muon detector (MD) array have been successfully operating, at an altitude of 4,300 m in Tibet, China since 2014. The gamma-ray energy and arrival direction are determined by the surface AS array, while the underground MD array enables us to drastically suppress the background cosmic rays above 100 TeV, by means of counting the number of muons in an air shower. Using these Tibet AS+MD arrays, we have succeeded for the first time in observing gamma rays above 100 TeV from the Crab Nebula [Amenomori et al. PRL, 123, 051101 (2019)] and the Galactic plane [Amenomori et al. PRL, 126, 141101 (2021)]. In this presentation, we will review recent observations with the Tibet ASgamma experiment and discuss the most powerful cosmic-ray source “PeVatron” in our Galaxy.
| Submitted on behalf of a Collaboration? | Yes |
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