Design optimization of the proximity focusing RICH with dual aerogel radiator using a maximum-likelihood analysis of Cherenkov rings

The use of a sequence of aerogel radiators with different refractive indices in a proximity focusing Cherenkov ring imaging detector has been shown to improve the resolution of the Cherenkov angle. In order to obtain further information on the capabilities of such a detector, a maximum-likelihood analysis has been performed on simulated data, with the simulation being appropriate for the upgraded Belle detector. The results show that by using a sequence of two aerogel layers with different refractive indices, the K/πK/π separation efficiency is improved in the kinematic region above 3 GeV/c  . In the low momentum region, the focusing configuration (with n1n1 and n2n2 chosen such that the Cherenkov rings from different aerogel layers at 4 GeV/c overlap) shows a better performance than the defocusing one (where the two Cherenkov rings are well separated).