Study on the sensitivity in detecting crab nebula by ARGO-YBJ experiment

A "full coverage" air shower array, ARGO (Astrophysical Radiation with Groundbased Observatory) experiment is under construction currently at YangBaJing in Tibet, China. Its altitude of 4,300m above see level is equivalent to an atmospheric depth of 606g/cm(2). ARGO experiment makes use of a full-coverage detector consisting of a layer of single gap Resistive Plate Chambers (RPC). The phase I detector, including a central (74 x 78m(2)) part and a guard ring in Size of 6400m(2). will be operated in 2005. One of the main goals of ARGO is to detect VHE gamma ray emission from galactic and extraglactic sources. With full Monte-Carlo simulation we studied the detector's angular resolution and found that the angular resolution Strongly depends on the number of fired pads N-pads. With three statistical methods we estimated ARGO's sensitivity in detecting Crab Nebula. According to our simulation, in one year's operation, Crab Nebula A will be detected by ARGO with a statistical significance of about 18 standard deviation without appeying any gamma/hadron identification technique.