[1] CESR was a particle accelerator designed to collide electrons and positrons at a center-of-mass energy of approximately 10 GeV.
Once the CUSB experiment was discontinued in the late 1980s, CLEO then spent most of its time at the Υ(4S)[8] and measured many important properties of the B mesons.
[10] When the BaBar and Belle B factories began to collect large amounts of data in the early 2000s, CLEO was no longer able to make competitive measurements of B mesons.
Between the proposal for and construction of CESR and CLEO, Fermilab discovered the Υ resonances and suggested that as many as three states existed.
[35] The shutdown for the installation of DR2 allowed ARGUS to beat CLEO to the observation of B mixing, which was the most cited measurement of any of the symmetric B experiments.
Observation of time-dependent asymmetries in the production of certain flavor-symmetric final states (such as J/Ψ K0S) was an easier way to detect CP violation in B mesons, both theoretically and experimentally.
[44] After losing the competition for the B factory, CESR and CLEO proceeded with a two-part plan to upgrade the accelerator and the detector.
[45] The silicon detector provided excellent vertex resolution, allowing precise measurements of D0, D+, Ds and τ lifetimes and D mixing.
With the advent of the high luminosity BaBar and Belle experiments, CLEO could no longer make competitive measurements of most of the properties of the B mesons.
CLEO-c was the final version of the detector, and it was optimized for taking data at the reduced beam energies needed for studies of the charm quark.
It replaced the CLEO III silicon detector, which suffered from lower-than-expected efficiency, with a six layer, all stereo drift chamber (ZD).
It operated at 1.5 T until CLEO-c, when the magnetic field was reduced to 1.0 T. The original CLEO detector used three separate tracking chambers.
The new drift chamber had the same outer radius as the original one so that it could be installed before the rest of the CLEO II upgrades were ready.
The axial sense wires had a half-cell stagger to help resolve the left-right ambiguity of the original drift chamber.
The inner and outer field layers of the chamber were cathode strips to make measurements of the longitudinal coordinate of tracks.
When the beampipe radius was reduced from 7.5 to 5.0 cm in 1986, a three-layer straw chamber (IV) was built to occupy the newly available space.
The IV was replaced during the CLEO II upgrade with a five-layer straw tube with a 3.5 cm inner radius.
The outer wall of the drift chamber was instrumented with 1 cm wide cathode pads to provide additional z measurements.
The silicon detector achieved 85% efficiency after installation, but soon began to suffer increasingly large inefficiencies.
[56] The silicon detector was replaced for CLEO-c because of its poor performance, the reduced need for vertexing capabilities, and the desire to minimize the material near the beampipe.
Five types of long-lived, charged particles are produced at CLEO: electrons, pions, muons, kaons and protons.
The outer portion of the CLEO detector was divided into independent octants that were primarily dedicated to charged particle identification.
[64] The dE/dx system demonstrated superior particle identification performance and aided in tracking, therefore in September 1981 all eight octants were equipped with dE/dx chambers.
[4] The CLEO I muon detector was far away enough from the interaction region that in-flight decays of pions and kaons were a significant background.
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 photons traveled through a nitrogen expansion volume, which allowed the cone angle to be precisely determined.
[38] 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|.
[34][35] Exclusive charmless semileptonic B meson decays were first observed by CLEO six years later in the modes B → πlν, ρlν,[72] and were used to determine |Vub|.
[41] These charmless hadronic decay modes can probe CP violation and are sensitive to the angles α and γ of the unitarity triangle.
Finally, CLEO observed many exclusive charmed decays of B mesons, including several that are sensitive to |Vcb|: B→ D(*)K*−,[83] B0→ D*0π0[84] B→ Λ+cpπ−, Λ+cpπ+π−,[85] B0→ D*0π+π+π−π−,[86] B0→ D*ρ′−,[87] B0→ D*−ppπ+, D*−pn,[62] B→ J/Ψ φ K,[88] B0→ D*+D*−,[89] and B+→ D0 K+.