Proton-Antiproton Collider

Hadron colliders

Schematics of the SppS complex
Intersecting Storage Rings	CERN, 1971–1984
Proton-Antiproton Collider (SPS)	CERN, 1981–1991
ISABELLE	BNL, cancelled in 1983
Tevatron	Fermilab, 1987–2011
Relativistic Heavy Ion Collider	BNL, 2000–present
Superconducting Super Collider	Cancelled in 1993
Large Hadron Collider	CERN, 2009–present
Future Circular Collider	Proposed

The Proton–Antiproton Collider (also known as the Super Proton–Antiproton Synchrotron, or SppS) was a particle accelerator that operated at CERN from 1981 to 1991. To operate as a proton-antiproton collider the Super Proton Synchrotron (SPS) underwent substantial modifications, altering it from a one beam synchrotron to a two-beam collider. The main experiments at the accelerator were UA1 and UA2, where the W and Z boson were discovered in 1983. Carlo Rubbia and Simon van der Meer received the 1984 Nobel Prize in Physics for their decisive contribution to the SppS-project, which led to the discovery of the W and Z bosons. Other experiments conducted at the SppS were UA4, UA5 and UA8.

Around 1968 Sheldon Glashow, Steven Weinberg, and Abdus Salam came up with the electroweak theory, which unified electromagnetism and weak interactions, and for which they shared the 1979 Nobel Prize in Physics. The theory postulated the existence of W and Z bosons. It was experimentally established in two stages, the first being the discovery of neutral currents in neutrino scattering by the Gargamelle collaboration at CERN, a process that required the existence of a neutral particle to carry the weak force — the Z boson. The results from the Gargamelle collaboration made calculations of the mass of the W and Z bosons possible. It was predicted that the W boson had a mass value in the range of 60 to 80 GeV/c², and the Z boson in the range from 75 to 92 GeV/c² – energies too large to be accessible by any accelerator in operation at that time. The second stage of establishing the electroweak theory would be the discovery of the W and Z bosons, requiring the design and construction of a more powerful accelerator.