Prospective annual detection rate of high energy gamma ray bursts with LHAASO-WCDA

The γ-ray bursts (GRBs) are the most violent explosion events in the universe ever since the Big Bang and can be served as the high redshift probes for cosmological study. Particularly, the observations on the GeV emission have had fruitful application, Such examples include the determination of the extra-galactic background light and stringent constraint on the Lorentz Invariance Violation effect. Owing to the advantages in very large effective area, the low threshold energy, the wide field of view and high duty cycle, the LHAASO-WCDA will have potential sensitivity in discovering the GRBs in 100 GeV energy region. In this work, a sample of GRBs has been generated and examined according to the observation of Fermi experiment. We extrapolate the Fermi spectra to high energy by taking into account the absorption due to the pair production process happening between gamma ray and extragalactic background light. With an assumption that ultra high energy component accounts for 10% of the total luminosity, we find that the LHAASO-WCDA has a GRB detection rate of ∼ 1/yr.