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On Nov. 11, 1974, two research teams rocked the particle physics world when they announced they had independently discovered a new subatomic particle – the J/psi. The particle’s existence called for a revision of what scientists had thought the universe was made of, and, practically overnight, entire physics textbooks had to be rewritten.

50 years later, on Nov. 8,  the Department of Energy’s SLAC National Accelerator Laboratory hosted a symposium to celebrate the 50th anniversary of the J/psi discovery, a key moment in modern particle physics now known as the .

Back in 1974, one team including researchers from SLAC (then called the Stanford Linear Accelerator Center) and Lawrence Berkeley National Laboratory had discovered the particle while crashing beams of electrons and positrons into each other at SLAC’s SPEAR ring collider. The other team, led by scientists from the Massachusetts Institute of Technology, had found the same particle at Brookhaven National Laboratory, where they smashed protons into a beryllium target. In 1976, SLAC’s Burton Richter and MIT’s Samuel Chao Chung Ting were awarded the for their teams’ discoveries.

The J/psi, a composite of a charm quark and its antimatter sibling, proved there was a previously unknown member in the family of quarks. The discovery was crucial in paving the way for our current understanding of the fundamental particles and forces in the universe, known as the . Today we know there are six types of quarks, including the fundamental building blocks of protons and neutrons found in everything we see around us.

Remembering the launch of a new era in particle physics

The Nov. 8 event drew a full house to SLAC’s Kavli Auditorium, with additional viewers tuning in online to honor the milestone that redefined particle physics. 

featured personal stories and insights from pioneering scientists, including several members of the original J/psi experiment teams. Sau Lan Wu, professor of physics at the University of Wisconsin, Madison, and a former MIT postdoc on Ting’s team, shared a memorable exchange between Ting and Richter at the time of the discovery, met with laughter by the audience: Ting told Richter he had “some interesting physics to tell” him, only to hear Richter reply with the exact same phrase.

Other speakers included Martin Breidenbach, William Chinowsky, Gary Feldman, Robert Hollebeek, Vera Lüth, Harvey Lynch, and Charles Morehouse, all co-authors of the seminal 1974 J/psi paper from SLAC and Berkeley Lab. Brookhaven Lab Director JoAnne Hewett also spoke, honoring , who led the SLAC/Berkeley Lab team to this extraordinary discovery.

Through spirited discussions and warm recollections, speakers brought the past to life while inspiring the audience with the legacy of the November Revolution. “The course of science was changed by the things that happened 50 years ago,” said SLAC Lab Director John Sarrao, who opened the symposium. “My wish for the future of SLAC is that we continue to have and continue to make more revolutions.”

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Brookhaven National Laboratory will celebrate the J/psi discovery as part of a on Nov. 22.

About SLAC

SLAC National Accelerator Laboratory explores how the universe works at the biggest, smallest and fastest scales and invents powerful tools used by researchers around the globe. As world leaders in and bold explorers of the physics of the universe, we forge new ground in understanding our origins and building a healthier and more sustainable future. Our  help develop new materials and chemical processes and open unprecedented views of the cosmos and life’s most delicate machinery. Building on more than 60 years of visionary research, we help shape the future by advancing areas such as quantum technology, scientific computing and the development of next-generation accelerators.

SLAC is operated by Stanford University for the U.S. Department of Energy’s . The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time.