The Tibet AS+MD Project; status report 2017

Abstract

We built a large (approximately 4,000 m 2 ) water Cherenkov-type muon detector array under the existing Tibet air shower array at 4,300 m above sea level, to observe 10-1000 TeV gamma rays from cosmic-ray accelerators in our Galaxy with wide field of view at very low background level. A gamma-ray induced air shower has significantly less muons compared with a cosmic-ray induced one. Therefore, we can effectively discriminate between primary gamma rays and cosmicray background events by means of counting number of muons in an air shower event by the muon detector array. We make a status report on the experiment.