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We search for steady TeV ν-rays from 18 pulsars in the Fermi-LAT pulsar catalog using the Tibet air shower array. We observe 8 sources including the Crab against expected 0.41 sources at a significance of 2σ or more among the 18 pulsars. The chance probability from Poisson statistics is estimated to be 1.4×10-8.With the Crab excluded, it is estimated to be 1.8×10-7. These low chance probabilities clearly show that the Fermi pulsars have a statistically significant correlation with TeV ν-ray excesses observed by the Tibet air shower array. [ABSTRACT FROM AUTHOR]

We propose to build a large water-Cherenkov-type muon-detector array (Tibet MD array) around the 37 000 m2 Tibet air shower array (Tibet AS array) already constructed at 4300 m above sea level in Tibet, China. Each muon detector is a waterproof concrete pool, 6 m wide × 6 m long × 1.5 m deep in size, equipped with a 20 inch-in-diameter PMT. The Tibet MD array consists of 240 muon detectors set up 2.5 m underground. Its total effective area will be 8640 m2 for muon detection. The Tibet MD array will significantly improve gamma-ray sensitivity of the Tibet AS array in the 100 TeV region (10-1000 TeV) by means of gamma/hadron separation based on counting the number of muons accompanying an air shower. The Tibet AS+MD array will have the sensitivity to gamma rays in the 100 TeV region by an order of magnitude better than any other previous existing detectors in the world. [ABSTRACT FROM AUTHOR]