No. 68 (00190, 00194) Family name : Ramos Given name : Ricardo Affiliation : Federal University of Rio de Janeiro Abbreviation : UFRJ / COPPE / EP E-mail address : ric3@lps.ufrj.br Title : A Matched Filter System for Muon Detection with Tilecal Authors : R. R. Ramos, J. M. Seixas and A. S. Cerqueira Abstract : The Level 1 (LVL1) trigger of the ATLAS detector relies very much in the calorimetry system, as both electromagnetic and hadronic calorimeters are fast and provide detailed information on the way classes of particles deposit their energy in the calorimeters. For the hadronic calorimeter (Tilecal) , the LVL1 trigger requires analogue signal summation along the three sampling layers (up to six calorimeter readout channels) of the calorimeter, forming the so called trigger tower signals. Each adder circuit also fanouts the information corresponding to the third layer of the calorimeter, which is used for muon detection. As muons deposit very small energy levels in the calorimeter, muon detection using Tilecal information from adder's muons output is performed under severe low signal-to-noise ratio conditions. In this paper, muon detection with Tilecal is developed using an optimal filter system that matches the response of the muon signal, which is treated as a random process. The detection system includes a whitening filter for proper treatment of the background noise, so that the matched filter based detection system can be considered optimal in the sense of the signal-to-noise ratio. Using experimental data from recent testbeam periods, a detection efficiency of 94% is achieved for a false alarm probability of 10%. In addition, the matched filter detection is compared with different classical methods currently being used by the Tilecal collaboration.