Detection of GRBs in Auger and the LAGO project

The detection of a high energy tail of photons from GRBs should be possible with the single particle counting technique. A group of detectors would detect a higher rate of events on a short time scale, of the order of the second. This technique has already been used with plastic scintillators. Use of water Cherenkov detectors gives a better sensitivity with respect to scintillators as secondary photons can be detected through their conversion in the water volume. This increases significantly the detection efficiency as the ratio photons to electrons in GRB photon showers is about 9 to 1 in the shower tail. The Pierre Auger Observatory, with 1600 water Cherenkov detectors, is a good candidate to check the efficiency of the technique. The Large Aperture GRB Observatory (LAGO) uses similar detectors at higher altitude (Puebla 4550m a.s.l., Chacaltaya 5250 m a.s.l.), and will bring better sensitivity to the high energy part of the GRB photon spectrum with much less surface to be covered