The Tibet air shower array, consisting of 533 scintillation counters which are placed in a lattice with 7.5 m spacing, has been in operation since 1999 at Yangbajing in Tibet, China at an altitude of 4,300 m above sea level. We found a modest discrimination between gamma- and proton-initiated air showers based on air shower profiles observed by the Tibet air shower array. This method is applied to the Crab Nebula as the standard gamma-ray source in the northern sky and excesses of anisotropy components, such as Tail-In region and the Cygnus arm direction, in multi-TeV energies. Further, we will try to judge whether these excesses are of gamma or proton origin, comparing our data between before discrimination and after discrimination.

The Tibet ASgamma Collaboration

Proceedings of the 30th International Cosmic Ray Conference; Rogelio Caballero, Juan Carlos D'Olivo, Gustavo Medina-Tanco, Lukas Nellen, Federico A. Sánchez, José F. Valdés-Galicia (eds.); Universidad Nacional Autónoma de México, Mexico City, Mexico, 2008; Vol. 3 (OG part 2), pages 1493-1494