Study of discrimination between cosmic gamma rays and protons at multi-TeV energies with the Tibet air shower array

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 gammaand 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. IC R C 2007 P rocedings P re-C onrence E dtion