Stanford physicists published the first experimental evidence of quarks
On 20 October 1969, researchers at the Stanford Linear Accelerator Center published results showing that high-energy electrons scattered off protons as if hitting point-like sub-particles.
The experiments directed high-energy electron beams from the two-mile linear accelerator at liquid hydrogen targets. When electrons bounced off at unusually wide angles, the data revealed that protons are not solid spheres, but composites made of smaller, point-like components originally termed partons and later identified as quarks.
The discovery confirmed theoretical predictions by Murray Gell-Mann and George Zweig, fundamentally reshaping modern physics and establishing the foundation for the Standard Model of particle physics.
Sources
- Physical Review Letters: Observed Behavior of Highly Inelastic Electron-Proton Scattering
- SLAC National Accelerator Laboratory History Archives
The earlier calendar listing linked to Wikipedia. This article was written from the Physical Review Letters publication.