Mainz 2014 – scientific programme
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T: Fachverband Teilchenphysik
T 3: Ultrahochenergetische kosmische Strahlung 1
T 3.1: Talk
Monday, March 24, 2014, 11:00–11:15, P3
A new method to search for ultra high-energy photons using the water-Cherenkov detectors of the Pierre Auger Observatory — •Lu Lu1,2 and Alan Watson2 for the Pierre Auger collaboration — 1University of Wuppertal, Germany — 2University of Leeds, United Kingdom
Photons with an energy of ∼1019 eV are expected to be detected if the highest-energy cosmic-rays are dominated by light nuclei (such as protons). Photons are also important for interpretations of astrophysical scenarios, for instance to constrain models of super-heavy dark-matter and magnetic monopoles.
On entering the atmosphere, they interact with particles in the air to create a cascade of around 10 billion secondary particles, known as an extensive air-shower. Compared to air showers initiated by hadronic primaries, photon showers contain few muons and are dominated by the electromagnetic component. Muons produced in showers travel in nearly straight lines while the electromagnetic component scatters and arrives on the ground with time delays. The FADC traces recorded from the water-Cherenkov detectors describe the energy deposited as a function of time. A new method – the entity method – uses both the shape of the mean time trace and the uncertainties in the early time bins to search for events that might have been initiated by photons. The likelihood method is used to identify photon-like time-traces. These are then combined with the likelihood from lateral distribution function fits. Photon upper limits based on the recent data of the Pierre Auger Observatory will be reported.