BERKELEY, Calif., Nov. 21, 2012 — Stuart Freedman, an investigator of fundamental physical laws and a nuclear physicist with Lawrence Berkeley National Laboratory and the University of California, Berkeley, died unexpectedly Nov. 9 while attending a conference in Santa Fe, N.M. He was 68.
Freedman used the radioactive decay of calcium atoms to rule out “local hidden variable” theories during his graduate work at UC Berkeley in 1972. He went on to exclude a number of other possible excursions from standard physics, including the existence of naked quarks, faster-than-light particles and very light Higgs bosons. He was also a leading authority on neutrinos, refuting widely heralded results suggesting that neutrinos have a mass of 17 keV — about 100,000 times heavier than current expectations.
Courtesy of Roy Kaltschmidt, Lawrence Berkeley National Laboratory
“Stuart started as a particle theorist but became an extraordinarily versatile and creative experimentalist, with a reputation for getting the right answer, often when others didn’t,” said Freedman’s friend and longtime associate, Berkeley Lab physicist Robert Cahn.
“He loved people with crazy ideas, if only for a good argument, and he was a source of brilliant ideas himself,” said Berkeley Lab’s Brian Fujikawa, who had worked closely with Freedman since 1984 and helped perform the decisive 17-keV experiment. “Stuart used a spectrometer that eliminated likely sources of error, and on top of that he created a small ‘fake’ signal by mixing carbon-14 into the sulfur-35 source whose decays we were measuring. Since we could detect that fake in the data, if there had been a real signal in the beta spectrum at 17 keV, we would have seen it.”
Some searches were less conclusive. Leading theorist Roberto Peccei of the University of California, Los Angeles, whose work with Helen Quinn led to the proposal of particles called axions, recalls writing an early paper with Freedman in 1978, when both were at Stanford. “It was called, appropriately, ‘Do axions exist?’ We are, incidentally, still asking the same question today.” Peccei confirms that Freedman “was not afraid to go against orthodoxy. In fact, he relished this role! The world has lost a wonderful physicist, but his impact on our field will remain.”
Freedman joined Argonne National Laboratory in 1982 and later became a professor in the University of Chicago’s Fermi Institute, where he “provided a crucial link between Argonne and the university,” said UChicago cosmologist Michael Turner. “Stuart provided the key connection to weak-interaction physics with his important experiments on the properties of neutrons and neutrinos.”
Freedman established the parameters of the weak interaction in the coupling of weak currents to the neutron. These measurements were crucial to understanding nuclear fusion, which made it “possible for us to determine the temperature at the center of the sun,” Cahn said.
In 1991, Freedman and his wife, Joyce, who had led the sponsored research office at UChicago, moved to Berkeley, joining Berkeley Lab and UC Berkeley while maintaining his affiliation with Argonne and Chicago. His fame for neutrino work grew, notably following the 2003 confirmation from the KamLand experiment in Japan that different neutrinos have different tiny masses and oscillate from one “flavor” to another. KamLand benefited from detector technology and signal processing contributed by US participation, inaugurated and led by Freedman.
“The KamLand oscillations result was one of Stuart’s proudest accomplishments,” said Jason Detwiler, an assistant professor at the University of Washington who met Freedman during the construction of KamLand and subsequently worked with him at Berkeley Lab for many years.
Freedman’s experimental style was “like a Grand Master in chess, always thinking many steps ahead,” Detwiler said. “He always had the clearest view of the science and the experiment’s essential rationale.”
Besides neutrino oscillations, Freedman’s contributions to neutrino science include KamLand’s detection of “geoneutrinos” originating from radioactive decays inside the Earth (See: Neutrino Detector Focuses on Earth
). He also played the role of US spokesperson and US construction project manager of the CUORE experiment at the Gran Sasso underground laboratory in Italy, a search for the as-yet-undetected process of neutrinoless double-beta decay; finding this would indicate that neutrinos are their own antiparticles.
He co-chaired studies, reports and surveys for the National Academy of Science, the National Research Council and the American Physical Society. At the time of his death, he was the leader of the Weak Interaction Group based in the Nuclear Science Division, a program that brings together international collaborations like KamLand and CUORE to examine the weak interaction between electrons and neutrinos and the quarks that constitute protons and neutrons.
“Somehow, Stuart just kept growing as a scientist,” said Gerald Garvey of Los Alamos, an experimental nuclear physicist and expert in science policy whose collaborations with Freedman began over 30 years ago. “Most of us start slowing down after 50, but Stuart continued to get stronger and stronger.”
He was named the Luis W. Alvarez Memorial Chair in Experimental Physics at UC Berkeley in 1999 and has received numerous awards and honors, including election to the National Academy of Science in 2001 and the 2007 Tom W. Bonner Prize for Nuclear Physics from the American Physical Society.
Freedman is survived by his wife, Joyce; his son, Paul, and daughter-in-law, Emily; his sister, Ina Jo Scheid; nephew Jason Sturman; and two grandchildren.
For more information, visit: www.lbl.gov