ALEPH was a

particle detector In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify ionizing particles, such as those produced by nu ...

at the Large Electron-Positron collider (LEP). It was designed to explore the physics predicted by the Standard Model and to search for physics beyond it.

Detector

The ALEPH detector was built to measure events created by

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

positron collisions in LEP. It operated from 1989 to 1995 in the energy range of the Z particle (around 91 GeV) and later (1995 to 2000) above the threshold of W pair production (up to 200 GeV). Typical events have many particles distributed in jets over the entire detector volume. The event rate ranged from around 1 Hz at the peak of the Z to at least a factor hundred smaller at the highest energies. The ALEPH detector was therefore designed to accumulate, for each event, as much information over as much

solid angle In geometry, a solid angle (symbol: ) is a measure of the amount of the field of view from some particular point that a given object covers. That is, it is a measure of how large the object appears to an observer looking from that point. The poi ...

as was practical. This was achieved by a cylindrical arrangement around the beam pipe with the electron-positron interaction point in the middle. A magnetic field of 1.5 Tesla was created by a

superconducting Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike ...

coil 6.4 m long and 5.3 m in diameter. The iron return yoke was a dodecagonal cylinder with two end-plates that left holes for a focusing magnet (quadrupole) of the LEP machine. The iron was 1.2 m thick and was subdivided into layers that left space for the insertion of layers of streamer tubes. In this way the iron yoke was a fully instrumented

hadron In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the e ...

calorimeter A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimete ...

(HCAL), which was read out in 4608 projective towers. Outside the iron, there were two double layers of streamer tube chambers to record the position and angle of muons that had penetrated the iron. Inside the coil was the electron-photon

(ECAL), designed for the highest possible angular resolution and electron identification. It consisted of alternating layers of lead and proportional tubes read out in 73,728 projective towers, each subdivided into three depth zones. The central detector for charged particles was the

time projection chamber In physics, a time projection chamber (TPC) is a type of particle detector that uses a combination of electric fields and magnetic fields together with a sensitive volume of gas or liquid to perform a three-dimensional reconstruction of a particl ...

(TPC), 4.4 m long and 3.6 m in diameter. It provided a three dimensional measurement of each track segment. In addition, it provided up to 330

ionisation Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecu ...

measurements for a track; this was useful for particle identification. The TPC surrounded the inner track chamber (ITC); an axial-wire drift chamber with inner and outer diameters of 13 cm and 29 cm and a length of 2 m. It provided 8 track coordinates and a trigger signal for charged particles that came from the interaction point. Closest to the beam pipe, was a silicon strip vertex detector. For each track, this measured two pairs of coordinates, 6.3 cm and 11 cm away from the beam axis over a length of 40 cm along the beam line. The beam pipe, made out of beryllium, had a diameter of 16 cm. The vacuum inside was about 10⁻¹⁵ atm. ALEPH Website
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References

External links

Record for ALEPH experiment
on INSPIRE-HEP {{DEFAULTSORT:ALEPH Experiment CERN experiments Particle experiments