was far away enough from the interaction region that in-flight decays of pions and kaons were a significant background. The more compact structure of the CLEO II detector allowed the muon detectors to be moved closer to the interaction point. Three layers of muon detectors were placed behind layers of iron absorbers. The streamer counters were read out from each end to determine the z position. The CLEO III upgrade included the addition of the RICH subdetector, a dedicated particle identification subdetector. The RICH detector was required to be less than 20 cm in the radial direction, between the drift chamber and the calorimeter, and less than 12% of a radiation length. The RICH detector used the Cerenkov radiation of charged particles to measure their velocity. Combined with the momentum measurement from the tracking detectors, the mass of the particle, and therefore its identity, could be determined. Charged particles produced Cerenkov light as they pass through a LiF window. Fourteen rings of thirty LiF crystals comprised the radiator of the RICH, and the four centermost rings had a sawtooth pattern to prevent total internal reflection of the Cerenkov photons. The photons traveled through a nitrogen expansion volume, which allowed the cone angle to be precisely determined. The photons were detected by 7.5 mm × 8.0 mm cathode pads in a multi-wire chamber containing a methane-triethylamine gas mixture. Physics program CLEO has published over 200 articles in Physical Review Letters and more than 180 articles in Physical Review. The reports of inclusive and exclusive b → s γ have both been cited over 500 times. B physics was usually CLEO's top priority, but the collaboration has made measurements across a wide spectrum of particle physics topics. B mesons CLEO's most cited paper reported the first measurement of the flavor-changing neutral current decay b→sγ. The measurement agreed well with the Standard Model and placed significant constraints on numerous beyond the Standard Model proposals, such as charged Higgs and anomalous WWγ couplings. The analogous exclusive decay B+,0→ K*+,0 γ was also measured. CLEO and ARGUS reported nearly simultaneous measurements of inclusive charmless semileptonic B meson decays, which directly established a non-zero value of the CKM matrix element |Vub|. Exclusive charmless semileptonic B meson decays were first observed by CLEO six years later in the modes B → πlν, ρlν, and were used to determine |Vub|. CLEO also discovered many of the hadronic analogs: