The W Boson Weighs In

"They look like W's, they feel like W's, they smell like W's, they must be W's!" So Carlo Rubbia is said to have remarked as he pondered evidence for the existence of the W boson in January 1983. The discovery, made by the rival UA1 and UA2 experiments at CERN's Super Proton Synchrotron (SPS), was a historic moment in particle physics – with Rubbia and the UA1 collaboration narrowly beating the UA2 experiment to the prize (see "Carlo Rubbia and the discovery of the W and the Z" on pages 23–28). The discovery of the Z boson followed hot on the heels of the W in June and together they put the Standard Model of particle physics on a solid footing.