Performance of the LiF-TEA ring imaging Cherenkov detector at CLEO
We describe the particle identification capability of the CLEO RICH system. This system consists of a 1 cm thick LiF radiator coupled to a photon detector that uses wire proportional chambers filled with a mixture of CH4 and TEA. We discuss the yield of photoelectrons observed per ring and the angular resolution. We show the efficiencies achieved for particle identification and the associated fake rates from data collected with both CLEO III and CLEO-c detectors. Finally we show examples of the particle separation ability which is excellent for both CLEO III and CLEO-c data.
Evidence for $B^{(*)}_s$ Production at the ϒ(5S)
Based on data collected by the CLEO III detector at CESR, we started a series of investigations to open the mysteries of the ϒ(5S) resonance decay properties. Bs mesons are expected to decay predominantly into Ds meson, while the lighter B mesons decay into Ds only about 10% of the time. We exploit this difference to present the first evidence of a substantial production of Bs mesons at the ϒ(5S) resonance. We make here a preliminary model dependent estimate of the ratio of to the total quark pair production at the ϒ(5S) energy to be (21 ± 3 ± 9)%.
The CERES RICH detector system
Abstract We describe the two RICH detectors of the CERES electron pair spectrometer at the CERN SPS which are used for electron identification and, in conjunction with a novel silicon drift detector, for tracking in pp, pA and AA collisions. The RICH detectors are operated at a high γ th ⋍ 32 (CH4 at 1 atm.) and are thus rather insensitive to hadrons. The UV-detectors are multistep counters with a multiwire chamber as the last stage. They are operated at gains of 2–4 × 105 using a mixture of He + 6% C2H6 (or CH4) + TMAE. The two UV-detectors are equipped with 53 800 (48 400) square pads. The front end electronics consists of modules with 256 (121) channels, based on a 64-channel charge-sensitive preamplifier VLSI chip. The total readout time is 280 (1600) μs per event. Subsets of the pad data are used as input to a fast trigger processor selecting events with at least two separated electron rings. The trigger achieved an enrichment factor of ∼ 100 in proton-induced interactions, and a factor of ∼3 in 32SAu collisions. The RICH detectors perform very close to their design values. We observe clean Cherenkov rings with an average number of 11.2 (12.5) photons/ring. This is consistent with the calculated value N0 = 131 (75) cm−1 within the systematical error of about 10%. The spatial resolutions of 1.0 and 0.8 mrad (rms) for individual photons are dominated by chromatic aberration and in very good agreement with theoretical expectations.