The photon veto system for the NA62 rare kaon decay experiment

Three possible solutions for a system of large-angle vetoes (LAV) have been analyzed and tested in order to choose the best option for the NA62 experiment, expected to take data in 2011/12 at CERN. The rejection power assured by the veto system, whose goal is mainly to veto photons from the K + → π + π 0 and K + → π + π 0 π 0 decays, is a key-point to collect ∼ 100 events of the K + → π + ν ν ¯ decay ( BR ∼ 10 - 10 ) with a total background (BG) of the order of 10%, thus providing a very stringent test of the Standard Model (SM) and a measurement of the V td element of the Cabibbo–Kobayashi–Maskawa (CKM) matrix. The details of this study and the final decision taken will be reviewed in this paper.