CLEO (particle detector)

CLEO was a general purpose <a href="/facts/Particle_detector/rYj0qKtA">particle detector</a> at the <a href="/facts/Cornell_Electron_Storage_Ring/GkE1q9PF">Cornell Electron Storage Ring</a> (CESR), and the name of the collaboration of physicists who operated the detector. The name CLEO is not an acronym; it is short for <a href="/facts/Cleopatra_VII_of_Egypt/zxUlkxUF">Cleopatra</a> and was chosen to go with CESR (pronounced <a href="/facts/Julius_Caesar/ptR603Gv">Caesar</a>). CESR was a <a href="/facts/Particle_accelerator/Pkuc08xC">particle accelerator</a> designed to collide <a href="/facts/Electron/L0KBo5cW">electrons</a> and <a href="/facts/Positron/HgV4zBzA">positrons</a> at a center-of-mass energy of approximately 10 <a href="/facts/GeV/YMT1fqX9">GeV</a>. The energy of the accelerator was chosen before the first three <a href="/facts/Bottom_quark/2s4rJRSo">bottom quark</a> <a href="/facts/Upsilon_meson/Ap9wz1cs">Upsilon resonances</a> were discovered between 9.4 GeV and 10.4 GeV in 1977. The fourth Υ resonance, the Υ(4S), was slightly above the threshold for, and therefore ideal for the study of, <a href="/facts/B_meson/4669MSRM">B meson</a> production.
CLEO was a <a href="/facts/Hermetic_detector/jIfoeU5a">hermetic detector</a> that in all of its versions consisted of a <a href="/facts/Tracking_(particle_physics)/daUap6y2">tracking</a> system inside a solenoid magnet, a <a href="/facts/Calorimeter_(particle_physics)/FCA2evfS">calorimeter</a>, <a href="/facts/Particle_identification/90Asw9Ns">particle identification</a> systems, and a <a href="/facts/Muon/BP2fLVIR">muon</a> detector. The detector underwent five major upgrades over the course of its thirty-year lifetime, both to upgrade the capabilities of the detector and to optimize it for the study of B mesons. The CLEO I detector began collecting data in October 1979, and CLEO-c finished collecting data on March 3, 2008.
CLEO initially measured the properties of the Υ(1–3S) resonances below the threshold for producing B mesons. Increasing amounts of accelerator time were spent at the Υ(4S) as the collaboration became more interested in the study of B mesons.
Once the <a href="/facts/CUSB/p4poua5Q">CUSB</a> experiment was discontinued in the late 1980s, CLEO then spent most of its time at the Υ(4S) and measured many important properties of the B mesons.
While CLEO was studying the B mesons, it was also able to measure the properties of <a href="/facts/D_meson/o6pW8BLc">D mesons</a> and <a href="/facts/Tau_lepton/6DW8j6PC">tau leptons</a>, and discover many new charm <a href="/facts/Hadron/C0sd1zty">hadrons</a>. When the <a href="/facts/BaBar/qh6z0s5M">BaBar</a> and <a href="/facts/Belle_experiment/hor4Nxnp">Belle</a> <a href="/facts/B-Factory/NJUkVHbs">B factories</a> began to collect large amounts of data in the early 2000s, CLEO was no longer able to make competitive measurements of B mesons. CLEO revisited the Υ(1-3S) resonances, then underwent its last upgrade to CLEO-c. CESR ran at lower energies and CLEO measured many properties of the ψ resonances and D mesons. CLEO was the longest running experiment in the history of particle physics.

CLEO (particle detector) open-in-new

CLEO (particle detector)