The OPERA RPC system

Abstract

The OPERA experiment was designed to detect νμ→ντ oscillations through τ appearance in the CERN Neutrinos to GranSasso (CNGS) beam.The detector consists of two identical supermodules, each made by a target section followed by a muon spectrometer.The target sections are made of nuclear emulsion layers alternated to lead plates; a scintillator target tracker is used to locate the neutrino interactions.The muon spectrometers are composed of a dipole iron magnet, precision drift tubes and resistive plate chambers, used as trigger and as tracker.The experiment took data with the neutrino beam from 2006 to 2012, with limited statistics during the first two years. The RPC data taking ended in December 2012.Results about the RPC performance and the aging of the system are brieflypresented.The use of the RPC data in the OPERA analysis is also addressed.During the 2012 run, the OPERA RPC system was used to check the measurement of the neutrino velocity with a dedicated set-up in parallel to the standard DAQ of OPERA, to check the preliminary results of 2011and to improve the precision.For this measurement, the absolute response time of the detector was measured.Finally, RPC data were also used to determine the charge of the third observed τ candidate.