Observing muon decays in water Cherenkov detectors at the Pierre Auger Observatory

P. ALLISON; F. ARNEODO; X. BERTOU; N. BUSCA; P.L. GHIA; C. MEDINA; G. NAVARRA; L. NELLEN; H. SALAZAR IBARGUEN; S. RANCHON; M. URBAN; L. VILLASENOR

Pune, India

Conferencia; 29th International Cosmic Ray Conference; 2005

Muons decaying in the water volume of a Cherenkov detector of the Pierre Auger Observatory provide a useful calibration point at low energy. Using the digitized waveform continuously recorded by the electronics of each tank, we have devised a simple method to extract the charge spectrum of the Michel electrons, whose typical signal is about 1/8 of a crossing vertical muon. This procedure, moreover, allows continuous monitoring of the detector operation and of its water level. We have checked the procedure with high statistics on a test tank at the Observatory base and applied with success on the whole array.