Obituary: Burton Richter
Particle physicist who helped to transform the science of matter
Burton Richter, who has died aged 87, shared the 1976 Nobel Prize with Sam Ting for their discovery of a subatomic particle which triggered a revolution in the understanding of matter.
The hunt for the quark, now enshrined as one of the basic particles of matter, began in the late 1960s when scientists working at the 3km-long particle accelerator at Stanford University bombarded protons (which were then considered to be fundamental particles) with electrons.
The way the electrons bounced off led them to believe there were small hard points within the protons. In other words the “fundamental” protons were made of yet smaller particles. Nowadays it is agreed these smaller particles were quarks, the building blocks of protons, neutrons and numerous exotic particles known as mesons.
Theorists had been kicking round the concept of quarks for years but there were problems with the theory and many scientists saw quarks as abstractions rather than things which had a physical existence. So the Stanford scientists named these smaller particles “partons” – a term that did not carry the same theoretical baggage as “quark”.
In 1974, however, everything changed. Two new particles were found: one, called the psi, by Richter at Stanford, using the new Stanford Positron Electron Accelerating Ring (which accelerated electrons and positrons in opposite directions around a circular ring to cause high-energy collisions releasing new particles); the other, called the J, at Brookhaven National Laboratory, by Ting.
The two men met on November 11 and as Richter recalled: “Sam said to me, ‘Burt, I have some interesting physics to tell you about’. My response was, ‘Sam, I have some interesting physics to tell you about!'”
It was quickly decided the two particles were one and the same and after some debate the new particle became known as the J/psi meson.
Richter had been surprised when the Stanford machine produced the new particle. But the simultaneous discovery by Ting – using a different procedure – ruled out the possibility of a mistake.
As it turned out the odd behaviour of this new particle could only be explained according to the theory of quarks, which meant that there was now only one way to understand all other particles. Belief in quarks was no longer optional.
The “November revolution”, as it became known, marked the beginning of a new era of particle physics. Less than two years later, an unusually short period of time, Richter and Ting were summoned to Stockholm.
Before the J/psi discovery, standard theory included three quarks, known as up, down and strange.
Some theorists had suggested a fourth quark should exist. They gave it the whimsical name “charm” and it soon became clear that the J/psi was made of a charm quark paired with a charm antiquark, each circling the other.
Burton Richter was born on March 22, 1931 in Brooklyn to a textile worker and educated at Far Rockaway High School, Queens, and at the Massachusetts Institute of Technology, graduating in physics in 1952 and taking a doctorate in 1956.
He then joined Stanford University’s High-Energy Physics Laboratory, where he became an assistant professor of physics in 1960.
In 1963 he also joined the Stanford Linear Accelerator Center where, in the early 1970s, he designed the Stanford Positron Electron Accelerating Ring.
In the 1980s he oversaw the construction of the Stanford Linear Collider, which fired positrons and electrons at each other along straight trajectories. Later he turned to energy issues, becoming an advocate of nuclear power.
Richter, who died on July 18, is survived by his wife, Laurose, and a son and daughter.