München 2009 – scientific programme
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T: Fachverband Teilchenphysik
T 95: Kosmische Strahlung 3
T 95.8: Talk
Tuesday, March 10, 2009, 18:30–18:45, M118
Photon background for neutrino induced showers* — •Oana Tascau, Markus Risse, and Karl-Heinz Kampert — Bergische Universität Wuppertal
The Pierre Auger Observatory is sensitive to ultra high energy (UHE) neutrinos. In this study down-going, close to horizontal neutrinos are considered, because the amount of atmosphere traversed increases the interaction probability, thus the produced showers may be detected by Auger. The challenge lies in the identification of these neutrino induced showers in the background of down-going cosmic rays. Here we investigate the neutrino background that may arise from UHE photons within the experimental photon flux limits set so far. Photon induced showers are investigated to see how deeply they penetrate and how often this may occur close to the detector. There are 2 possible phenomena: 1. Photon showers may start to cascade deep in the atmosphere, due to a suppression of the Bethe-Heitler cross-section by the Landau-Pomeranchuck-Migdal (LPM) effect. 2. Very deep sub cascades might occur also after the main depth of shower maximum from LPM-suppressed high-energy secondaries. High statistics Corsika simulations show the existence of near-horizontal photon showers which develop close to the detector. These showers could be mis-identified as neutrino candidates, thus the fraction of the rare showers which may have a late Xmax, above 2000 g/cm2, is determined. A total of 150 000 showers for various angle and energy bins were generated and analyzed. The photon background for neutrino searches with Auger is calculated. * Gefördert durch die BMBF Verbundforschung Astroteilchenphysik.