The Lateral Trigger Probability function for the Ultra-High Energy Cosmic Ray showers detected by the Pierre Auger Observatory

In this paper we introduce the concept of Lateral Trigger Probability (LTP) function, i.e., the probability for an Extensive Air Shower (EAS) to trigger an individual detector of a ground based array as a function of distance to the shower axis, taking into account energy, mass and direction of the primary cosmic ray. We apply this concept to the surface array of the Pierre Auger Observatory consisting of a 1.5 km spaced grid of about 1600 water Cherenkov stations. Using Monte Carlo simulations of ultra-high energy showers the LTP functions are derived for energies in the range between 10(17) and 10(19) eV and zenith angles up to 65 degrees. A parametrization combining a step function with an exponential is found to reproduce them very well in the considered range of energies and zenith angles. The LTP functions can also be obtained from data RI Chiavassa, Andrea/A-7597-2012; Verzi, Valerio/B-1149-2012; Chinellato, Carola Dobrigkeit /F-2540-2011; Fauth, Anderson/F-9570-2012; de souza, Vitor/D-1381-2012; Todero Peixoto, Carlos Jose/G-3873-2012; Shellard, Ronald/G-4825-2012; Caramete, Laurentiu/C-2328-2011; Petrolini, Alessandro/H-3782-2011; Albuquerque, Ivone/H-4645-2012; Muller, Marcio Aparecido/H-9112-2012; D'Urso, Domenico/I-5325-2012; Bleve, Carla/J-2521-2012; martello, daniele/J-3131-2012; Valino, Ines/J-8324-2012; Brogueira, Pedro/K-3868-2012; Chinellato, Jose Augusto/I-7972-2012; Yushkov, Alexey/A-6958-2013; Falcke, Heino/H-5262-2012; Beatty, James/D-9310-2011; Anjos, Joao/C-8335-2013; Sarkar, Subir/G-5978-2011 OI Shellard, Ronald/0000-0002-2983-1815; D'Urso, Domenico/0000-0002-8215-4542; Brogueira, Pedro/0000-0001-6069-4073; Falcke, Heino/0000-0002-2526-6724; Sarkar, Subir/0000-0002-3542-858X

In this paper we introduce the concept of Lateral Trigger Probability (LTP) function, i.e., the probability for an Extensive Air Shower (EAS) to trigger an individual detector of a ground based array as a function of distance to the shower axis, taking into account energy, mass and direction of the primary cosmic ray. We apply this concept to the surface array of the Pierre Auger Observatory consisting of a 1.5 km spaced grid of about 1600 water Cherenkov stations. Using Monte Carlo simulations of ultra-high energy showers the LTP functions are derived for energies in the range between 10(17) and 10(19) eV and zenith angles up to 65 degrees. A parametrization combining a step function with an exponential is found to reproduce them very well in the considered range of energies and zenith angles. The LTP functions can also be obtained from data