OPAL (detector)
The OPAL detector was an experiment at the LEP - storage ring of CERN , which collected data from 1989 to 2000.
The name is an acronym for " O mni P urpose A pparatus at L EP".
aims
In the first phase of the LEP, which was operated from 1989 to 1995, which was mass energy at about 90 GeV and in the region of Z 0 - mass , d. H. the data collected during this time were used to a large extent to precisely measure the mass of this very particle.
In November 1995 the LEP was operated for about a month with a main energy of 130 to 140 GeV (LEP 1.5), before the second expansion stage (LEP2) was completed in July 1996 with energies up to over 200 GeV. With this higher energy, pairs of W bosons could now be created, on the basis of which the standard model of particle physics was further checked.
construction
Around the point of collision between electrons and positrons , the individual detectors were attached one behind the other in a shell-like construction . The primary detector, i.e. the detector closest to the collision, has to prove the location of the resulting particles most precisely from all subsequent detectors. At OPAL, these were the so-called vertex semiconductor detectors . These were then followed by the jet chambers and the Z chambers, which recorded the traces of the particles in order to use them and the like. a. to be able to infer the impulse . The next bowl consisted of calorimeters , which recorded the energy of the particles. The last layer consisted of the muon detectors, which were both concentric around the other detectors and formed the end caps of the detector.
Results
The publications that were and are still being made in the course of the OPAL experiment run into the thousands, which is why only the most relevant results are listed here:
- Exact measurement of the Z 0 mass
- Generation of the W boson pairs and study of the decay products as a test of the electroweak force
- Look for clues about the Higgs mechanism