[2] It began running in 1972, colliding electrons and positrons with an energy of 3 GeV.
During the 1970s, experiments at the accelerator played a key role in particle physics research, including the discovery of the J/ψ meson (awarded the 1976 Nobel Prize in Physics), many charmonium states, and the discovery of the tau (awarded the 1995 Nobel Prize in Physics).
The latest major upgrade of the ring in that finished in 2004 rendered it the current name SPEAR3.
[1] Though the name Stanford Positron Electron Asymmetric Ring is also used in official sources.
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