The NA58 experiment, or COMPASS (Common Muon and Proton Apparatus for Structure and Spectroscopy) is a fixed-target particle physics

Particle physics

Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...

 experiment at the Super Proton Synchrotron

Super Proton Synchrotron

The Super Proton Synchrotron is a particle accelerator of the synchrotron type at CERN. It is housed in a circular tunnel, in circumference, straddling the border of France and Switzerland near Geneva, Switzerland. The SPS was designed by a team led by John Adams, director-general of what was...

, a particle accelerator

Particle accelerator

A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...

 at the European Organization for Nuclear Research (CERN

CERN

The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...

). It is a two-level magnetic spectrometer with calorimeters

Calorimeter (particle physics)

In particle physics, a calorimeter is an experimental apparatus that measures the energy of particles. Most particles enter the calorimeter and initiate a particle shower and the particles' energy is deposited in the calorimeter, collected, and measured. The energy may be measured in its...

 in both levels and particle

Subatomic particle

In physics or chemistry, subatomic particles are the smaller particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles...

 identification in the first level.

There are several research projects underway at COMPASS:

• understanding the contribution of the gluon
  Gluon
  Gluons are elementary particles which act as the exchange particles for the color force between quarks, analogous to the exchange of photons in the electromagnetic force between two charged particles....
  
  s to the spin
  Spin (physics)
  In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...
  
   of the proton
  Proton
  The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
  
   and other nuclei
  Atomic nucleus
  The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
  
  ,
• production and investigation of exotic meson
  Exotic meson
  Non-quark model mesons include#exotic mesons, which have quantum numbers not possible for mesons in the quark model;#glueballs or gluonium, which have no valence quarks at all;...
  
  s,
• production and investigation of charmed
  Charm quark
  The charm quark or c quark is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks...
  
   mesons.

About 240 physicists from 11 countries and 28 institutions work in COMPASS. Until the start of the LHC experiments, COMPASS was the largest experiment at CERN taking data. It has also been a pioneer in adopting new detector and readout technologies such as Micromega

Micromegas detector

The “Micromegas “ detector is a gaseous particle detector coming from the development of wire chamber. Invented in 1992 by Georges Charpak and Ioannis Giomataris, the Micromegas detectors are mainly used in experimental physics, in particular in particle physics, nuclear physics and astrophysics...

 and GEM

Gas Electron Multiplier

The Gas Electron Multiplier is a type of gaseous ionization detector used in nuclear and particle physics and radiation detection.All gaseous ionization detectors are able to collect the electrons released by ionizing radiation, guiding them to a region with a large electric field, and thereby...

detectors.

External links

• Collaboration Web site.
• COMPASS experimental setup.
• "COMPASS homes in on the nucleon spin", The CERN Courier, 25 July 2006 (accessed 26 June 2008).