Burton Richter (1931–2018) Physicist Who Helped to Discover the First Particle Containing a Charm Quark

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COMMENT OBITUARY Burton Richter (1931–2018) Physicist who helped to discover the first particle containing a charm quark.

he burst of scientific activity that machines. To achieve even-higher-energy began with the discovery of the J/ψ collisions, Burt long advocated setting up particle in 1974 is known to parti- two linear accelerators head-to-head. He Tcle physicists as the ‘November revolution’, instigated efforts to plan one, but such because it so radically changed their per- a machine has yet to be built. spective. Charm quarks, heavier than Richter recognized that SLAC had to the quarks that make up protons and diversify to survive. When SPEAR was neutrons, were predicted by theory that under construction, condensed-matter became the standard model of particle physicists Sebastian Doniach and William physics. Finding particles containing them Spicer at Stanford University convinced EDDIE ADAMS/AP/REX/SHUTTERSTOCK opened up a new chapter in physics. him to add a small window in the vacuum Burton Richter, who died on 18 July, pipe of the storage ring, so that the X-rays made that revolution possible by designing produced by circulating electrons or and building the positron–electron accel- positrons could get out. This created the erator SPEAR and an innovative detector most intense X-ray source then available, facility, both at the Stanford Linear opening the door to X-ray science. Intense Accelerator Center (SLAC) in California. X-ray pulses have many applications in Richter received the 1976 Nobel Prize in materials science, chemistry and in deci- Physics for the J/ψ discovery. (The double phering biological structures. Today, this name for the particle is because two exp- science is one of the main uses of SLAC. erimental groups announced their results where he spent the rest of his career. He Richter also brought particle astro- on the same day; Samuel Ting, who led the was director of SLAC from 1984 until 1999, physics to the science mix at the lab, and other experiment, shared the Nobel prize.) and remained involved in physics research supported a plan to convert the SLAC It has to be said that Burt was not and policy until the day he died. accelerator into the world’s first X-ray looking for this particle. He agreed to Particle physicists generally fall into laser (itself a tour de force of accelerator let his colleagues, Marty Breidenbach, one of three categories: theorist, experi- design) to produce pulses of even-more- Vera Lüth and Roy Schwitters, “waste mentalist or accelerator physicist. Each intense X-rays. a weekend” (as he put it) to redo meas- requires specialized expertise, and so few Burt served the community in other urements to check an anomaly in their people master more than one. Burton ways. He was a member of the JASON data. They found this new particle Richter was the exception. He excelled at group, providing technical advice to the immediately — noting in the log book designing and building accelerators, as US government. He served on countless that the data “came pouring in”. Within well as designing and leading experiments national and international science- months, they made further discoveries that used them. advisory panels, and as councillor and that confirmed their interpretation of the Richter’s enthusiasm for storage president of the American Physical particle as a charm quark. rings — accelerators in which particles Society. His interest in energy policy led This breakthrough would not have circulate for hours — began at Stanford. to his encyclopaedic book Beyond Smoke happened without Richter’s energy and With physicist Gerald O’Neill of Princeton and Mirrors: Climate Change and Energy persistence. Most physicists did not see University, in New Jersey, Richter helped in the 21st Century. SPEAR as a priority, and the US Congress to build the world’s first pair of rings to Burt Richter cared about ideas, not would not fund it. After years of rejections, store electrons. SPEAR was his next pro- status or recognition. He would share his Richter redesigned the project to cut costs. ject, with electrons and positrons held in a technical insight and acumen with anyone He convinced his laboratory director and single ring. The positron–electron project to improve an experiment. If a postdoc or the Atomic Energy Commission to let (PEP), a larger and higher-energy storage student had a good idea, he would support him build it using ongoing funding. Once ring, came online at SLAC in 1980. it; if he disagreed with a high-status scien- repackaged as an improvement to an exist- Burt was keen to push for ever-higher tist, he made it clear. He argued furiously ing facility, rather than a new project, it particle energies. To produce lots of in the service of getting to the answers, did not need congressional approval. Z-particles, a carrier of the weak nuclear and expected others to do the same. He Burton Richter was born in Brooklyn, force, he invented the SLAC linear collider. gave responsibility to those he found most New York, on 22 March 1931, and grew Short pulses of high-energy electrons and capable, without regard to seniority. up in Queens, another borough of the positrons, in beams the width of a human Burt loved doing physics, constructing city. Graduating from high school with hair, travel for miles along the SLAC experiments capable of reaching frontiers a passion for science experiments, he accelerator. They pass along separate arcs and breaking beyond them. ■ enrolled at the Massachusetts Institute of and then collide, occasionally producing Technology, Cambridge, where he obtained Z-particles. The collider yielded, among Helen Quinn is a theoretical physicist and his undergraduate degree in 1952 and his other results, a tight upper bound on professor emerita at SLAC, where she did her PhD in physics four years later. He moved the mass of the Higgs boson and, just as PhD and spent most of her career as a staff to Stanford University and in 1963 to the importantly, it demonstrated the viability scientist and faculty member. new Stanford Linear Accelerator Center, of the linear-collider concept for future e-mail: [email protected]