Search for TeV GRBs using Tibet ASγ data

TeV energy emission from gamma ray bursts （GRB） is very important for studying the origin and the radiation mechanism of GRB. Searching for TeV GRBs is carried out by using the Tibet ASγ data. A GRB candidate is a shower cluster appearing in a given small sky window and a given time interval. An equi-zenith-angle method is used to estimate the background. In this analysis，two methods are applied in searching for possible GRBs signals，one considers the coincidence with satellite GRB data and the other doesnt. No significant TeV GRBs is detected in either case. The upper flux limit on top of the atmosphere at the 95% confidence level is estimated to be about 3.32×10 -9 —1.24×10 -7 cm -2 ·s -1 accordingly.