N A 62 RICH

The N A 62 experiment at CERN, aimed to measure K+ → π+νν branching fraction (Ο(1011)), relies on a gas-based RICH detector for π/μ separation and L 0 trigger. A first prototype of such a detector has been built and tested in 2007; it is a full length (18 m) Ne-filled vessel equipped with a spherical mirror and 96 P Ms on its focal plane, ≅ 17 m upstream the mirror. This prototype has been tested at CERN Sps on a 200 GeV/c pion beam mainly as a first check of its time resolution and of the light collection technique; the time resolution has been found to be about 65 ps, and the light collection, i.e. the number of hit P Ms per ring, fairly as expected.