A Monte Carlo method to generate fluorescence light in extensive air showers Vitor de Souza * , Henrique Barbosa, Carola Dobrigkeit Instituto de Fı ´sica Gleb Wataghin, Universidade Estadual de Campinas, 13083-970 Campinas-SP, Brazil Received 3 December 2003; received in revised form 1 July 2004; accepted 15 July 2004 Available online 20 August 2004 Abstract A new approach to simulate fluorescence photons produced in extensive air showers is described. A Monte Carlo program based on CORSIKA produces the fluorescence photons for each charged particle in the development of the shower. This method results in a full three-dimensional simulation of the particles in a shower and of the fluores- cencelightgeneratedintheatmosphere.Thephotonsproducedbythisprogramaretrackeddowntoatelescopeandthe simulationofaparticulardetectorisapplied.Thedifferencesbetweenthismethodandone-dimensionalapproachesare quantitativelydeterminedasafunctionofthedistancebetweenthetelescopeandtheshowercore.Asaparticularappli- cation,themaximumdistanceatwhichtheAugerfluorescencetelescopemightbeabletomeasurethelateraldistribu- tion of a shower is determined as a function of energy. Ó 2004 Elsevier B.V. All rights reserved. PACS: 96.40.Pq Keywords: Cosmic-ray; Fluorescence telescopes; Simulation 1. Introduction There are several questions yet to be solved about cosmic rays with energy above 10 18 eV. The most exciting topics concern the existence of a cut-off in the energy spectrum, the possible anisotropy of the sources, the chemical composi- tion and the propagation mechanisms. Particles with these energies arrive on the Earth with a very low flux and therefore can only be studied by the detection of the extensive air showers (EAS) they produce in the atmosphere. The present HiRes [1] and the AGASA [2] exper- iments have contributed to our understanding of the nature of high energy cosmic rays and future detectors(Auger [3],EUSO [4],OWL [5] andTele- scope Array [6])areverypromisingduetothein- crease in collection area and the use of new technologies. 0927-6505/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.astropartphys.2004.07.006 * Corresponding author. E-mail address: vitor@ifi.unicamp.br (V. de Souza). Astroparticle Physics 22 (2004) 263–273 www.elsevier.com/locate/astropart