Burton Richter

Burton Richter, born in 1931, American physicist and Nobel laureate. In 1976, Richter shared the Nobel Prize for physics with American physicist Samuel C.C. Ting for their independent discoveries of the subatomic particle J/psi.

Born in New York City, Richter received his bachelor's degree in 1952 and his doctoral degree in 1956 from the Massachusetts Institute of Technology (MIT). In 1956 he became a research associate at Stanford University. He was made an assistant professor at Stanford in 1960, and became an associate professor at the Stanford Linear Accelerator Center (SLAC) in 1963. In 1967, he was made a full professor of physics at Stanford. He served as the director of SLAC from 1984 to 1999.

Richter's research focused on high-energy particle physics, the study of subatomic particles moving extremely fast. To explore this field, physicists have built particle accelerators, devices used to speed charged elementary particles to high energies. The accelerators Richter used at MIT were cyclotrons, which move particles in a spiral path as they gained speed, and synchrotrons, which move particles in a circular path. Both these accelerators direct the high-energy particles at stationary atoms when the particles have reached the desired speed. The linear accelerator at SLAC can generate positively charged particles as well as the negatively charged particles used in other accelerators. Because of the particles' opposite charges, the magnetic field used to contain and accelerate them affect them differently. The positively charged particles, or positrons, move through the accelerator counterclockwise, while the negatively charged particles, or electrons, move clockwise in the same area. Thus physicists can create much higher-energy collisions between the two moving beams of particles than they could with one moving beam of particles and stationary atoms.

In 1973, Richter began experimenting with a device, called the Stanford positron-electron accelerating ring (SPEAR), designed to create those high-energy collisions between positrons and electrons. When the positrons and electrons collided, they produced a burst of electromagnetic energy out of which other particles were produced. In 1974, Richter's group was studying the rate at which such collisions produced hadrons, a class of particles related to the proton and neutron. They noticed that the production rate of hadrons peaked sharply, often a sign of a new particle, at a particular energy. Richter gave the new particle the name psi. At the same time, Ting had discovered the particle using a different technique at MIT. Ting had named the particle J, so the two names were joined into J/psi. The discovery of the J/psi particle gave experimental evidence of the theorized fourth elementary particle known as a quark. This fourth quark was called charm.