Studies on wrapping materials and light collection geometries in plastic scintillators

The KOPIO experiment at BNL was intended to measure the branching ratio of the ultra-rare (SM prediction about 3×10-113×10-11) decay K0→π0νν¯ with a precision of O(10%)O(10%).Highly efficient veto systems are required to keep background from kaon decays with additional photons or charged particles under control. The planned charged particle veto system consists of about 40m2 organic scintillator operated in vacuum and aims at efficiencies >99.99%>99.99%. To reach the required 50keV detection threshold a very high light collection efficiency has to be achieved. We here report on our extensive studies of light guide geometries and different wrapping materials used to maximize light collection.