Oreste Piccioni 1915-2002
"Pinocchio, Niels Bohr called our experiment Pinocchio, the false puppet," explained Oreste Piccioni in a recent presentation to the students of the Liceo Virgilio in Rome, about the experiment he performed with Marcello Conversi and Ettore Pancini in the same liceo during the Second World War. "And nobody believed us at first. But our results were crystal clear and the paper of Fermi, Teller and Weisskopf put them in the proper perspective: the mesotron wasn't the particle of Yukawa, but a new kind of electron-like particle."
Born in 1915 in Siena, Italy, Piccioni graduated from the University of Rome in 1938 under Enrico Fermi. In 1942 he and Conversi started a direct precision measurement of the mesotron lifetime and tests of the behaviour of positive and negative mesotrons. According to contemporary theories, mesotrons, the penetrating component of cosmic rays, were the mediators of the strong force foreseen by Yukawa; therefore the negative mesotrons had to be more likely captured by nuclei, while the positive ones (repelled by positively charged nuclei) undergo spontaneous decay with higher probability.
After the bombing of the Rome University campus in July 1943, the researchers moved to the Liceo Virgilio, near the Vatican, which they hoped would be better protected. "We hid ourselves from the Nazis until the liberation of Rome in June 1944. Working in those days required guts." Then they were joined by Ettore Pancini, who graduated in Padua with Bruno Rossi and was a resistance leader in northern Italy. The team used magnetic lenses to distinguish between positive and negative mesotrons and fast electronic anti-coincidence detection. "Electronic tubes were not available and we had to build them by ourselves." Their striking result, published in 1947, demonstrated that negative mesotrons in light absorbers, like carbon, almost always decayed instead of being captured by the positive nucleus. The mesotron was not the Yukawa particle. Many authors, including Bethe and Alvarez, have frequently quoted their experiment as the one marking the origin of modern particle physics.
In 1946, Piccioni emigrated to the US, first at MIT with Bruno Rossi and then at Brookhaven National Laboratory, where he developed fast electronic circuitry - reaching a resolving time of 3 ns in 1954 - and devised a magnetic scheme to eject, steer and focus fast proton beams at the Cosmotron.
Based on his expertise in magnetic optics, Piccioni suggested a detecting scheme based on quadrupole focusing lenses and time-of-flight measurements to the Berkeley group lead by Emilio Segrè hunting for antiprotons at the newly built Bevatron. The experiment successfully detected antiprotons in 1955, and the achievement won Segrè and Chamberlain the 1959 Nobel prize.
In September 1955 Piccioni joined Berkeley where, with a beautiful experiment, he demonstrated the existence of antineutrons produced by antiprotons, and detected (by a spectrograph containing five quadrupole lenses) two timed-flight paths to eliminate pions simulating antiprotons. He remained proud of this discovery: "Everybody was convinced of the existence of antiprotons since the discovery of positrons in 1932, for reasons of symmetry, and it was only a question of an accelerator with the necessary energy. On the other side, there were much less compelling reasons for an antiparticle of the neutron, being electrically neutral".
Afterwards, Piccioni turned his attention to the puzzling properties of neutral kaons. With Abraham Pais, he developed the theory of "regeneration" of kaons: since the long-lived KL is a superposition of K0 and K0, the crossing of matter will upset the fine balance between the two amplitudes and therefore what will emerge will not be a pure KL but a superposition of KL and of the short-lived KS. With the help of a powerful Berkeley team, Piccioni experimentally confirmed the regeneration prediction.
At CERN at the end of 1960, Piccioni collaborated in the construction of the first secondary beam of antiprotons; his was the analogue computer used for studying the optics of the beam, based on magnetic deflectors and quadrupoles. Also in 1960, he became a professor at the University of California at San Diego (UCSD), where he founded the experimental particle physics group, which is involved in major experiments worldwide. He retired from UCSD in 1986, becoming a professor emeritus, and devoted himself to working on the foundations of quantum mechanics.
Piccioni felt he had been deprived of recognition for contributions to the discovery of the antiproton, and in 1972 he sued the two prize-winners. The courts dismissed the lawsuit, saying it had been filed too late. His challenge to the establishment triggered discussions in the scientific community on the social aspects of research and on professional ethics.
Oreste Piccioni died on 13 April at his home in Rancho Santa Fe, California. Our community has lost a combative pioneer in particle physics, a highly skilled experimentalist and a brilliant and creative genius.
Alessandro Pascolini, INFN Padua.
Boyce D McDaniel 1917-2002
On 8 May 2002 Boyce D McDaniel, emeritus professor and former director of the Cornell University Laboratory of Nuclear Studies, died of a heart attack at the age of 84 at his home in Ithaca, New York.
Mac, as he was known to everyone, came to Cornell as a graduate student in 1940 after a BA degree at Ohio Wesleyan University and an MA at Case School of Applied Science. As a graduate student of Robert Bacher, he built one of the first multichannel neutron time-of-flight spectrometers and used it to make precision measurements of the energy levels of indium. After his Cornell PhD in 1943 he spent a few months at MIT as a post-doc and the rest of the war years at Los Alamos working on the Manhattan Project. He returned to Cornell in 1946 as a faculty member in the Department of Physics.
Mac was a versatile experimenter in nuclear, particle and accelerator physics. He worked on each of the Cornell machines, the 2 MeV cyclotron (the first outside of Berkeley), the 0.3, 1, 2 and 10 GeV electron synchrotrons, and the Cornell Electron-Positron Storage Ring (CESR). The pair spectrometer, which he invented for the study of gamma-ray transitions in nuclear reactions, was the standard instrument for precision gamma spectroscopy for many years. He was a pioneer in sophisticated time-of-flight measurements and led the first experiments on strange particle photoproduction in the 1950s and 1960s.
Mac's prowess as a technical problem solver and accelerator expert was legendary. Besides having a vital role in the design, construction and successful operation of each of the Cornell machines, he spent several years leading the commissioning of the Fermilab accelerator. He was not only a master at making complex technical systems work, but also a skilled scientific leader. Mac served under Bob Wilson as associate director of the Cornell laboratory from 1960, becoming director in 1967 when Wilson left for Fermilab. He continued and enhanced Wilson's aggressive do-it-yourself effort to keep Cornell at the forefront of particle physics and accelerator development. In the late 1970s he spearheaded the effort to extend the reach of the 10 GeV synchrotron by adding an electron-positron storage ring in the same tunnel. The very successful CESR run of the past 23 years and the simultaneous exploitation of the by-product X-ray radiation by the CHESS laboratory could not have happened without Mac's crucial leadership in the early years. He would always be pitching in where the need was greatest - in the accelerator tunnel, the control room, the machine shop, or in Washington. Nothing was left to chance.
After his nominal retirement in 1985, Mac continued to serve the laboratory and the high-energy physics community. At CESR he took an active role in upgrade projects, designing and installing magnets and instrumentation, participating in control room accelerator dynamics experiments, building things and making them work. Other laboratories and agencies relied on Mac for his wisdom and experience. He served as trustee of Associated Universities Inc. (Brookhaven) and of Universities Research Association (Fermilab). He served on ICFA and HEPAP and was chairman of the board of overseers of the SSC. He helped guide many other projects for the NSF and DOE.
Mac's colleagues at Cornell and high-energy physicists everywhere will greatly miss his technical skills, leadership, wisdom, kindness, and his unselfish efforts for the general good.
Mac is survived by his wife Jane, daughter Gail and son Jim. A memorial get-together is being planned for the autumn.