Tests of a proximity focusing RICH with aerogel as radiator

TL;DR

This paper reports on the construction and testing of a proximity focusing RICH detector using aerogel as a radiator, analyzing its resolution and photon detection efficiency in a beam test.

Contribution

It provides experimental measurements of Cherenkov angle resolution and photon yield using aerogel radiators with multianode PMTs, highlighting limitations and potential improvements.

Findings

Cherenkov angle resolution matches estimates from pixel size and emission point

Detected photon number aligns with aerogel and detector characteristics

Photon yield is limited by Rayleigh scattering and detector dead space

Abstract

Using aerogel as radiator and multianode PMTs for photon detection, a proximity focusing Cherenkov ring imaging detector has been constructed and tested in the KEK $\pi$2 beam. The aim is to experimentally study the basic parameters such as resolution of the single photon Cherenkov angle and number of detected photons per ring. The resolution obtained is well approximated by estimates of contributions from pixel size and emission point uncertainty. The number of detected photons per Cherenkov ring is in good agreement with estimates based on aerogel and detector characteristics. The values obtained turn out to be rather low, mainly due to Rayleigh scattering and to the relatively large dead space between the photocathodes. A light collection system or a higher fraction of the photomultiplier active area, together with better quality aerogels are expected to improve the situation. The reduction of Cherenkov yield, for charged particle impact in the vicinity of the aerogel tile side wall, has also been measured.