Time-of-propagation (TOP) counter tested in LEPS at SPring-8

We have tested a time-of-propagation (TOP) counter which is a ring-image Cherenkov counter utilizing position and propagating time of Cherenkov light produced by particles moving in a quartz radiator. Position sensitive photomultipliers are attached to the end of quartz bar to detect the produced Cherenkov-ring image. Velocity of the charged particle was determined by comparing the time-of-propagation spectra of the Cherenkov light with results of Monte Carlo simulation. From analysis of the test experiment using 1.22 GeV/c electron beam at SPring-8, we determined velocity of the electron beam as 1.001 with a resolution of 0.002. On the basis of this study, we designed a full set-up of the detector for separating pion and kaon for the momentum region from 1.5 to 2.0 GeV/c by more than three standard deviations-separation level.