Study on the sensitivity of high energy GRB detection with a 22500 m 2 water Cherenkov array at 5200 m altitude

HAWC experiment is currently under construction in Mexico at altitudes of 4100 m a.s.l and the energy threshold can be as low as a few hundred GeV. Owing to the large field of view and high duty cycle, HAWC is capable for observing high energy GRBs. Traveling through cosmological distance, gamma rays with energy higher than 100 GeV are strongly attenuated due to the pair production interaction between gamma rays and extra-galactic background lights. It is crucial to further decrease the energy threshold down to tens of GeV. Recently, some interesting candidate sites were found in Pumajiangtang (5200 m a.s.l) of Tibet, China. Based on full MC simulation, this work shows that the effective area for 50 GeV at 5200 m is 4 times larger than that at 4100 m. By adopting the popular GRB model parameters, 1 ∼ 2 high energy GRBs are expected to be observed every year with a HAWC-like experiment at 5200 m.