The search for the W boson

To find the W boson, CERN converted Europe's largest accelerator, the Super Proton Synchrotron, into the world's first proton-antiproton collider. The bold move paid off 

08 06, 1976
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At the International Neutrino Conference in Aachen, Germany, (8-12 June 1976) physicists Carlo Rubbia, Peter McIntyre and David Cline suggest modifying the Super Proton Synchrotron (SPS) from a one-beam accelerator into a two-beam collider. The two-beam configuration would collide a beam of protons with a beam of antiprotons, greatly increasing the available energy in comparison with a single beam colliding against a fixed target.

Their paper on the subject, Producing Massive Neutral Intermediate Vector Bosons with Existing Accelerators is published in the conference proceedings the following year.

17 06, 1976
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At 2.2 kilometres in diameter the Super Proton Synchrotron is Europe's largest particle accelerator. Commissioning of the accelerator begins in mid-March 1976 using beams of protons. Then on 17 June 1976 the SPS accelerates a beam of protons at its design energy of 400 GeV for the first time. The machine is ready to supply beams to experiments.

19 02, 1971
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The Super Proton Synchrotron is designed to provide protons at 400 GeV for fixed-target experiments. Construction for this underground synchrotron begins on 19 February 1971.


10 08, 1972
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Simon van der Meer at CERN writes a paper describing a technique he had first though of in 1968 to reduce the energy spread and angular divergence of a beam of charged particles. During this process of "stochastic cooling", the particles are "compressed" into a finer beam with less energy spread and less angular divergence. By increasing the particle density to close to the required energy, this technique improved the beam quality and, among other things, brings the discovery of the W boson within reach.