Page 94 - Building Big Data Applications

Chapter 4 Scientific research applications and usage 89

ElectronePositron Collider (LEP), one of the largest particle accelerators ever
constructed.
LEP collided electrons with positrons at energies that reached 209 GeV. It was a
circular collider with a circumference of 27 km built in a tunnel roughly 100 m (300 ft)
underground and used from 1989 until 2000. Around 2001 it was dismantled to make
way for the LHC, which reused the LEP tunnel. The LEP is the most powerful accelerator
of leptons ever built. LEP was built with four detectors, each 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 energy, momentum, and charge, thus
allowing physicists to infer the particle reaction that had happened and the elementary
particles involved. By performing statistical analysis of this data, knowledge about
elementary particle physics is gained. The four detectors of LEP were called Aleph,
Delphi, Opal, and L3. They were built differently to allow for complementary
experiments. The colliders and detectors created and used were the following:
ALEPH is an acronym for Apparatus for LEP PHysics at CERN. ALEPH is a detector
that determined the mass of the W-boson and Z-boson to within one part in a
1000. The number of families of particles with light neutrinos was determined to
be 2.982 0.013, which is consistent with the standard model value of 3.
DELPHI Is an acronym for DEtector with Lepton, Photon, and Hadron
Identification. Like the other three detectors, it recorded and analyzed the result of
the collision between LEP’s colliding particle beams. DELPHI was built in the
shape of a cylinder over 10 m in length and diameter, and a weight of 3500 tons.
In operation, electrons and positrons from the accelerator went through a pipe
going through the center of the cylinder, and collided in the middle of the detector.
The collision products then traveled outwards from the pipe and were analyzed by
a large number of subdetectors designed to identify the nature and trajectories of
the particles produced by the collision.
OPAL is an acronym for Omni-Purpose Apparatus for LEP. The name of the experi-
ment was a play, 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 Germany. OPAL was designed and built as 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.
L3 was another LEP experiment. Its enormous octagonal magnet return yoke
remained in place in the cavern and became part of the ALICE detector for the LHC.
LEP was successful in many experiments and had provided enough directions to what
physics directions it could base on the standard model, however we felt the need to
create and build a larger collider which will give us beyond the standard model and