CERN

The convention establishing CERN was ratified on 29 September 1954 by 12 countries in Western Europe. The acronym CERN originally represented the French words for Conseil Européen pour la Recherche Nucléaire ('European Council for Nuclear Research'), which was a provisional council for building the laboratory, established by 12 European governments in 1952. During these early years, the council worked at the University of Copenhagen under the direction of Niels Bohr before moving to its present site near Geneva.

The acronym was retained for the new laboratory after the provisional council was dissolved, even though the name changed to the current Organisation européenne pour la recherche nucléaire ('European Organization for Nuclear Research') in 1954. According to Lew Kowarski, a former director of CERN, when the name was changed, the abbreviation could have become the awkward OERN, and Werner Heisenberg said that this could "still be CERN even if the name is [not]".

CERN's first president was Sir Benjamin Lockspeiser. Edoardo Amaldi was the general secretary of CERN at its early stages when operations were still provisional, and the first Director-General (1954) was Felix Bloch.

At the sixth session of the CERN Council in Paris from 29 June to 1 July 1953, the convention establishing the organization was signed, subject to ratification, by 12 states. The convention was gradually ratified by the 12 founding Member States: Belgium, Denmark, France, the Federal Republic of Germany, Greece, Italy, the Netherlands, Norway, Sweden, Switzerland, the United Kingdom, and Yugoslavia.

Several major achievements in particle physics have occurred in experiments at CERN. They include:

In September 2011, CERN attracted media attention when the OPERA Collaboration reported the detection of possibly faster-than-light neutrinos. Further tests showed that the results were flawed due to an incorrectly connected GPS synchronization cable.

The 1984 Nobel Prize for Physics was awarded to Carlo Rubbia and Simon van der Meer for the developments that resulted in the discoveries of the W and Z bosons. The 1992 Nobel Prize for Physics was awarded to CERN staff researcher Georges Charpak "for his invention and development of particle detectors, in particular the multiwire proportional chamber". …

CERN operates a network of seven accelerators and two decelerators, and some additional small accelerators. Each machine in the chain increases the energy of particle beams before delivering them to experiments or to the next more powerful accelerator. The decelerators naturally decrease the energy of particle beams before delivering them to experiments or further accelerators/decelerators. Before an experiment is able to use the network of accelerators, it must be approved by the various Scientific Committees of CERN. Currently (as of 2026) active machines are:

Many activities at CERN currently involve operating the Large Hadron Collider (LHC) and the experiments for it. The LHC represents a large-scale, worldwide scientific cooperation project.

The LHC tunnel is located 100 metres underground, in the region between Geneva International Airport and the nearby Jura mountains. The majority of its length is on the French side of the border. It uses the 27 km circumference circular tunnel previously occupied by the Large Electron–Positron Collider (LEP), which was shut down in November 2000. CERN's existing PS/SPS accelerator complexes are used to pre-accelerate protons and lead ions which are then injected into the LHC.

Eight experiments (CMS, ATLAS, LHCb, MoEDAL, TOTEM, LHCf, FASER and ALICE) are located along the collider; each of them studies particle collisions from a different aspect, and with different technologies. Construction for these experiments required an extraordinary engineering effort. For example, a special crane was rented from Belgium to lower pieces of the CMS detector into its cavern, since each piece weighed nearly 2000 tons. The first of the approximately 5000 magnets necessary for construction was lowered down a special shaft at in March 2005.

The LHC has begun to generate vast quantities of data, which CERN streams to laboratories around the world for distributed processing, making use of a specialized grid infrastructure, the LHC Computing Grid. In April 2005, a trial successfully streamed 600 MB/s to seven different sites across the world.

In August 2008, the initial particle beams were injected into the LHC. …

The smaller accelerators are on the main Meyrin site, also known as the West Area, which was originally built in Switzerland alongside the French border, but has been extended to span the border since 1965. The French side is under Swiss jurisdiction and there is no obvious border within the site, apart from a line of marker stones.

The SPS and LEP/LHC tunnels are almost entirely outside the main site, and are mostly buried under French farmland and invisible from the surface. They have surface sites at points around them, either as the location of buildings associated with experiments or other facilities needed to operate the colliders such as cryogenic plants and access shafts. The experiments are located at the same underground level as the tunnels at these sites.

Three of these experimental sites are in France, with ATLAS in Switzerland, and some of the ancillary cryogenic and access sites are in Switzerland. The largest of the experimental sites is the Prévessin site, also known as the North Area, which is the target station for non-collider experiments on the SPS accelerator. Other sites are the ones which were used for the UA1, UA2 and the LEP experiments. The latter are used by LHC experiments.

Outside of the LEP and LHC experiments, most are officially named and numbered after the site where they were located. For example, NA32 was an experiment looking at the production of so-called "charmed" particles and located at the Prévessin (North Area) site. WA22 used the Big European Bubble Chamber (BEBC) at the Meyrin (West Area) site to examine neutrino interactions. The UA1 and UA2 experiments were considered to be in the Underground Area, i.e. situated underground at sites on the SPS accelerator.

Most of the roads on the CERN Meyrin and Prévessin sites are named after famous physicists, such as Niels Bohr, who pushed for CERN's creation. Other notable names are Richard Feynman, Albert Einstein, and Wolfgang Pauli.

Since its foundation by 12 members in 1954, CERN regularly accepted new members. All new members have remained in the organization continuously since their accession, except Spain and Yugoslavia. Spain first joined CERN in 1961, withdrew in 1969, and rejoined in 1983. Yugoslavia was a founding member of CERN but quit in 1961. Of the 24 members, Israel joined CERN as a full member in January 2014, becoming the first, and currently only, non-geographically European full member.

The budget contributions of member states are computed based on their Net National Income at factor cost.

Also observers are the following international organizations:

Non-Member States (with dates of Co-operation Agreements) currently involved in CERN programmes are:

CERN also has scientific contacts with the following other countries and regions:

International research institutions, such as CERN, can aid in science diplomacy.

A large number of institutes around the world are associated to CERN through current collaboration agreements and/or historical links. The list below contains organizations represented as observers to the CERN Council, organizations to which CERN is an observer and organizations based on the CERN model:

.cern is a top-level domain for CERN. It was registered on 13 August 2014. On 20 October 2015, CERN moved its main website to home.cern.