Large Electron–Positron Collider
Geneva, Switzerland | |
Coordinates | 46°14′06″N 06°02′42″E / 46.23500°N 6.04500°E |
---|---|
Institution | CERN |
Dates of operation | 1989–2000 |
Succeeded by | Large Hadron Collider |
The Large Electron–Positron Collider (LEP) was one of the largest particle accelerators ever constructed. It was built at CERN, a multi-national centre for research in nuclear and particle physics near Geneva, Switzerland.
LEP collided electrons with positrons at energies that reached 209 GeV. It was a circular collider with a circumference of 27 kilometres built in a tunnel roughly 100 m (300 ft) underground and passing through Switzerland and France. LEP was used from 1989 until 2000. Around 2001 it was dismantled to make way for the Large Hadron Collider, which re-used the LEP tunnel. To date, LEP is the most powerful accelerator of leptons ever built.
Collider background
LEP was a circular lepton collider – the most powerful such ever built. For context, modern colliders can be generally categorized based on their shape (circular or linear) and on what types of particles they accelerate and collide (leptons or hadrons).
The shape of the collider is also important. High energy physics colliders collect particles into bunches, and then collide the bunches together. However, only a very tiny fraction of particles in each bunch actually collide. In circular colliders, these bunches travel around a roughly circular shape in opposite directions and therefore can be collided over and over. This enables a high rate of collisions and facilitates collection of a large amount of data, which is important for precision measurements or for observing very rare decays. However, the energy of the bunches is limited due to losses from synchrotron radiation. In linear colliders, particles move in a straight line and therefore do not suffer from synchrotron radiation, but bunches cannot be re-used and it is therefore more challenging to collect large amounts of data.
As a circular lepton collider, LEP was well suited for precision measurements of the electroweak interaction at energies that were not previously achievable.
History
Construction of the LEP was a significant undertaking. Between 1983–1988, it was the largest civil engineering project in Europe.[2]
When the LEP collider started operation in August 1989 it accelerated the electrons and positrons to a total energy of 45
Operation
LEP was fed with electrons and positrons delivered by CERN's accelerator complex. The particles were generated and initially accelerated by the LEP Pre-Injector, and further accelerated to nearly the speed of light by the Proton Synchrotron and the Super Proton Synchrotron. From there, they were injected into the LEP ring.
As in all
Detectors
The Large Electron–Positron Collider had four detectors, built around the four collision points within underground halls. Each was the size of a small house and was capable of registering the particles by their
ALEPH
ALEPH stands for Apparatus for LEP pHysics at CERN. The detector determined the mass of the
DELPHI
DELPHI stands for DEtector with Lepton, Photon and Hadron Identification.
OPAL
OPAL stands for Omni-Purpose Apparatus for LEP. The name of the experiment was a play on words, as some of the founding members of the scientific collaboration which first proposed the design had previously worked on the JADE detector at DESY in Hamburg.[4] OPAL was a general-purpose detector designed to collect a broad range of data. Its data were used to make high precision measurements of the Z boson lineshape, perform detailed tests of the Standard Model, and place limits on new physics. The detector was dismantled in 2000 to make way for LHC equipment. The lead glass blocks from the OPAL barrel electromagnetic calorimeter are currently being re-used in the large-angle photon veto detectors at the NA62 experiment at CERN.
L3
L3 was another LEP experiment.
Results
The results of the LEP experiments allowed precise values of many quantities of the
Higgs boson
Near the end of the scheduled run time, data suggested tantalizing but inconclusive hints that the
For years, this observation was the only hint of a Higgs Boson; subsequent experiments until 2010 at the
See also
References
- ^ Myers, Steve (September 11, 2019). "The Greatest Lepton Collider". CERN Courier. Retrieved 22 April 2022.
- ^ ISSN 0010-7514.
- ^ "Welcome to ALEPH". Retrieved 2011-09-14.
- ^ "The OPAL Experiment at LEP 1989–2000". Retrieved 2011-09-14.
- ^ "L3 Homepage". Retrieved 2011-09-14.
- arXiv:1007.4587 [hep-ex].)
{{cite arXiv}}
: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link - ^ "New results indicate that new particle is a Higgs boson - CERN". home.web.cern.ch. Archived from the original on 20 October 2015. Retrieved 24 April 2018.
External links
Media related to Large Electron–Positron Collider at Wikimedia Commons
- LEP Working Groups
- The LEP Collider from Design to Approval and Commissioning excerpts from the John Adams memorial lecture delivered at CERN on 26 November 1990
- A short but good (though slightly outdated) overview (with nice photographs) about LEP and related subjects can be found in this online booklet of the British Particle Physics and Astronomy Research Council.
- Experiment Record for LEP on INSPIRE-HEP