Beam test of a dual radiator Cherenkov detector with aerogel and wavelength-shifting acrylic plastic

Abstract The response of a wavelength shifting acrylic plastic has been determined for particles passing through the plastic and for Cherenkov light incident on the plastic from an external silica-aerogel radiator. The results have been obtained during a beam test at the KEK PS facility. The photoelectron yield for internally created Cherenkov light has been determined as a function of particle velocity. A comparison with an empirical parameterization gives rough estimates for the photon collection efficiency of 39% and 92% for internal Cherenkov emission below and above the critical angle for total internal reflection, respectively. A comparatively low efficiency of ≈13% for external light is likely due to losses in the external aerogel radiator.