Progress of the NA62 RICH detector

NA62 is the last generation Kaon experiment at CERN. Its main goal is to collect about 100 K+ →π+vv events with 10% background. This implies to collect more than 1013 K+ decays with a backgound rejection factor better than 1012. The challenging aspect of the experiment is the suppression of Kaon decays with branching ratioes up to 10 orders of magnitude higher than the signal and similar experimental signature, such as K+ → μ+v. To this purpose good PID (Particle IDentification) and kinematic rejection are required. Precise timing is also needed to correctly associate the π + with the parent K+ in an high rate environment. A RICH (Ring Imaging Cherenkov) detector is proposed as PID element, to identify μ contaminating the π sample in the 15-35 GeV/c momentum range with inefficiency lower than 1% and to measure the arrival time with precision smaller than 100 ps. It will also be a key element for the NA62 trigger. A vacuumproof cylindrical vessel with 4m diameter, 17m long, will be filled with Neon gas at atmospheric pressure. The Cherenkov light will be reflected by a mosaic of 20 hexagonal mirrors with 17mfocal length and collected by 2000 photomultipliers. The progress in the construction of the detector is described: the installation will start in January 2014, with completion foreseen in time for the first physics run of the NA62 experiment in the fall of 2014.