Composition sensitive parameters measured with the surface detector of the Pierre Auger Observatory

PIERRE AUGER COLLABORATION (J. ABRAHAM, ... , A. MARIAZZI, ET AL)

Merida, Mejico

Conferencia; 30th International Cosmic Ray Conference; 2007

A key step towards the understanding of the origin ofultra-high energy cosmic rays is their mass composition.Primary photons and neutrinos produce markedly differentshowers from nuclei, while showers of nuclear species arenot easy to distinguish. To maximise the discriminationwith the Pierre Auger Observatory ideally all mass-sensitiveobservables should be combined, but the 10% duty cycle ofthe fluorescence telescopes largely prevents the use ofhybrid data, and therefore of the depth of shower maximum,for the very highest energies.Therefore, we investigate mass-sensitive observables accessible with the surface detectors alone. These include the signal risetime in the Cherenkov tanks, the curvature of the shower front, the asymmetry of the signal in azimuth, and various methods to assess the muon-to-electromagnetic ratio. The mass sensitivity of these variables is demonstrated and their application for composition studies is discussed.