Detection of GRB with Water Cherenkov Detectors Xavier Bertou Instituto Balseiro Denis Allard University of Chicago

Water Cherenkov Detector EAS Detector Want uniform answer to incoming particles Diffuse Cherenkov Cone Xavier Bertou - RICH 2004 - Mexico

The single Particle Technique We want to study the high energy (above 100 MeV) component of the GRB spectrum At these energies, photon showers give only isolated particles at ground level A GRB would be seen by an EAS array as an increase in background counting rate on the whole array Xavier Bertou - RICH 2004 - Mexico

Xavier Bertou - RICH 2004 - Mexico Photon Flux Photon Showers Xavier Bertou - RICH 2004 - Mexico

Photon Shower Simulation 250 millions showers generated: Corsika 6.0 No thinning 50 MeV to 100 GeV 0, 10, 20 and 30° zenith angle Ground at 1400 m (Auger) Xavier Bertou - RICH 2004 - Mexico

Auger Mean number is very small The number of particles decreases with the zenith angle For the lowest energy showers the probability to reach the ground is very low Xavier Bertou - RICH 2004 - Mexico

Particles at ground level Photons dominate: Cherenkov detectors welcome! Xavier Bertou - RICH 2004 - Mexico

independent of primary energy! Secondary spectrum Secondary spectrum independent of primary energy! Photon spectrum Electron spectrum Xavier Bertou - RICH 2004 - Mexico

Going to higher altitude Xavier Bertou - RICH 2004 - Mexico

Altitude/Zenith effect: Overall flux normalization Xavier Bertou - RICH 2004 - Mexico

Xavier Bertou - RICH 2004 - Mexico Detector Simulation we simulated 200 000 photons and e+e- with SDSim between 1 and 100 MeV and arrival direction between 0 and 60° Estimation of the probability to detect secondary particles as a function of their nature, energy and arrival direction Xavier Bertou - RICH 2004 - Mexico

Simple detector trigger Xavier Bertou - RICH 2004 - Mexico

90% of detected secondaries are photons Cherenkov tanks are efficient GRB detectors Xavier Bertou - RICH 2004 - Mexico

Guetta & Granot ApJ 2003 (=600 t=1s) Auger GRB model: Guetta & Granot ApJ 2003 (=600 t=1s) Xavier Bertou - RICH 2004 - Mexico

What could be done in Auger Tanks talk to central every second: Set low threshold and just count Use 1-fold trigger for low energy particle Send the count every second to central At Central: Moving window of one minute Look for “n” sigma effect Currently: We can apply this method to T2 rates Only a proof of concept Xavier Bertou - RICH 2004 - Mexico

Astroparticle Physics: recycling welcome! Conclusions Cherenkov tanks are efficient GRB detectors Auger is at low altitude but it’s big: Could see something Easy to implement (and free) Projects at higher altitude: 4200 m (Puebla) 5200 m (Chacaltaya ?) Astroparticle Physics: recycling welcome! Xavier Bertou - RICH 2004 - Mexico