The LHCb collaboration observes a new class of particles composed of five quarks, called pentaquarks. Later, in 2020, LHCb reports the observation of a particle composed of four quarks, a tetraquark. In addition to two-quark and three-quark particles, which include protons and neutrons, the quark model predicts the existence of other composite states of quarks,…

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The Large Electron-Positron (LEP) collider is decommissioned in November. Over its 11 years of operation, from 1989 to 2000, it has produced 17 million Z bosons, uncharged mediators of the weak force, and approximately 40 000 pairs of W bosons, charged mediators of the weak force. The precision measurements conducted at LEP have provided stringent tests…

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The Antiproton Decelerator (AD) starts delivering low-energy antiprotons to antimatter experiments. This 188-metre-long machine decelerates antiprotons so that they can be trapped by experiments. The aim is to study antimatter in depth to determine any difference compared to ordinary matter. In 2017, a newer deceleration ring, ELENA (Extra Low ENergy Antiproton), is connected to the…

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A combination of results from several experiments provides evidence for the existence of Quark–gluon plasma (QGP), a state of matter believed to have existed just after the Big Bang. The experiments all measured different aspects of collisions between the nuclei of heavy atoms and a fixed target at the Super Proton Synchrotron (SPS). This result…

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The Large Hadron Collider project is approved in December. The successful tests of several superconducting magnets demonstrate the feasibility of this innovative machine. The civil engineering works to build the new service tunnels and experimental caverns start in 1998 and are completed in 2005. The development and production of the LHC components, including the impressive…

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The Large Electron-Positron collider (LEP) is commissioned in July 1989. With its 27-km circumference, the LEP is the largest accelerator ever built. Fed by CERN’s accelerator complex, it provides particle collisions to four enormous detectors – ALEPH, DELPHI, L3, and OPAL.

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Only a year after the discovery of the W and Z bosons, the two key scientists behind it receive the Nobel Prize in Physics. Carlo Rubbia, the instigator of the SPS accelerator’s conversion into a proton-antiproton collider and spokesperson of the UA1 experiment, shares the prize with Simon van der Meer, inventor of the stochastic…

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The Isotope Separator On-Line Device (ISOLDE), a nuclear research experiment, comes into service in October. Over the years, ISOLDE has grown to provide beams of atomic nuclei for several dozen experiments annually. Fundamental research at ISOLDE ranges from studies of the structure of atomic nuclei to materials science, radiation protection, life sciences and astrophysics.

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On 13 September, the French and Swiss states sign an agreement to extend the CERN site across the French-Swiss border, in preparation for the construction of a new machine – the Intersecting Storage Rings (ISR) – due to start the following year. With this expansion, CERN becomes the only research centre in the world to…

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A team led by Antonino Zichichi using the Proton Synchrotron at CERN, and a team led by Leon Lederman at the Brookhaven National Laboratory (USA), simultaneously observe the antideuteron, the antimatter nucleus composed of an antiproton and an antineutron. This discovery is an important step in understanding how antimatter behaves.

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