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| ALEPH | Apparatus forLEPPHysics |
|---|---|
| DELPHI | DEtector withLepton,Photon andHadronIdentification |
| OPAL | Omni-PurposeApparatus forLEP |
| L3 | Third LEP experiment |
OPAL was one of the major experiments atCERN'sLarge Electron–Positron Collider. OPAL studied particles and their interactions by collecting and analysing electron-positron collisions. There were over three-hundred physicists from 32 institutions involved in the collaboration.[1]
LEP was the largestparticle accelerator in the world. OPAL was one of four detectors associated with LEP, alongsideALEPH,DELPHI andL3.[2]
The OPALdetector was about 12 m long, 12 m high and 12 m wide. The detector components were arranged around the beam pipe, in a layered structure like that of an onion. The tracking system of OPAL consisted of a silicon microvertex detector, a vertex detector, a jet chamber, and z-chambers (from the beam pipe out).
The silicon microvertex detector and the vertex chamber were used to locate decay vertices of short-lived particles, and to improve the momentum resolution.[3] The central jet chamber identified particles from how muchionization they caused, and how far they curved in the magnetic field. These chambers worked well to identify tracks in the plane perpendicular to the beam axis. They were complemented by so-called "z-chambers" at the outside edge of the jet chamber, to provide precise measurements of the perpendicular coordinates of the tracks.[4]
Further out from the beam pipe, OPAL's calorimeter system was divided into electromagneticcalorimeters (mostly made of lead-glass blocks),hadron calorimeters (part of the return yoke of the magnet, largely made of iron) and forward calorimeters placed around, and close to, the beam pipe at the two ends of the detector to catch particles thrown forwards by collisions in LEP.[5] The end caps of the detector were also equipped withmuon detectors.
In its first phase of operation from 1989 to 1995,electrons andpositrons collided in LEP at 91 GeV. The aim was to produceZ bosons. OPAL accumulated millions of theseZ events for high-precision measurements. In LEP's second phase from 1996 to 2000, the collider's collision energy was increased to make pairs ofW bosons, and to search for possible new particles andnew physics.[6]
| Large Hadron Collider (LHC) | |
|---|---|
| Large Electron–Positron Collider (LEP) | |
| Super Proton Synchrotron (SPS) | |
| Proton Synchrotron (PS) | |
| Linear accelerators | |
| Other accelerators | |
| ISOLDE facility | |
| Non-accelerator experiments | |
| Future projects | |
| Related articles | |
