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Synergy

Throughout the course of particle physics, results from one accelerator have stimulated discoveries at another. Early experiments smashing protons on protons produced new particles but did not reveal the structure of the proton itself. Finally experiments with electron beams discovered that protons are made of quarks and gluons. Later experiments showed clearly how quarks and gluons are distributed inside the proton – a requirement for understanding collisions at proton colliders. Experiments at electron-positron colliders discovered that high-energy quarks and gluons produce “jets” of particles inside detectors. Soon, physicists discovered such jets in collisions at a new CERN proton-antiproton collider. Jets are now a tool in all searches for new particles whose decays involve quarks and gluons.

The discovery of the J/psi particle at SLAC and Brookhaven in 1974 revealed the charm quark and antiquark. The proton-proton Intersecting Storage Rings were in operation at CERN, but the “trigger” for ISR detectors was set to detect different phenomena and missed the J/psi. Redesigning the detectors with different triggers allowed observation of the J/psi and showed how it is produced by the strong interactions in proton-proton collisions.

After the discovery at Fermilab of the Upsilon, containing the bottom quark, electron-positron machines soon found a whole spectrum of related particles. They led to an understanding of the strong force that binds quarks to antiquarks and to measurements of the properties of the bottom quark.

Electron-positron collider detectors equipped to measure submillimeter distances around a collision point allowed physicists to separate the point where the b quark is produced from the vertex of tracks at the point where it decays. Using this telltale “displaced vertex” of the b quark in top quark decays, experimenters discovered the top at the Tevatron collider.