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1976 Nobel Prize for Physics 1976 Nobel Prize for Physics Burt Richter (left) with his wife Laurose A smiling Sam Ting at his experiment at the enjoy a joke with Stan Flatte during the party CERN Intersecting Storage Rings where he at SLAC to celebrate the Nobel prize award. continues the search for leptons which has (Photo Stanford News Service) dominated his research life. ... to be shared equally between Professor Burton Richter, Stanford Linear Accelerator Center USA, and Professor Samuel C.C. Ting, Massa­ chusetts Institute of Technology Cam­ bridge USA, for their pioneering work in the discovery of a heavy elementary particle of a new kind.' With this citation the physics Nobel Prize went to Burt Richter and Sam Ting who led the teams which found the J/psi particle just two years ago. It is rare that discoveries are so rapidly recognized by the highest award in science. This reflects the dramatic effect of J/psi on the world of high energy physics — so dramatic that since the events of 1974, we talk of 'the new physics'. Sam Ting was born in the USA in 1936 of Chinese parents. His early years were spent in China in a Uni­ versity environment but without regular schooling until he was 12 years old. At the age of 20 he returned to the USA and took a physics degree at the University of Michigan. His first schooling in experimental techniques was at Berkeley with W. Jones and Martin Perl and then at CERN with Giuseppe Cocconi. He worked at CERN with Marcel Vivargent Klaus Winter and Gustaf Weber. In 1965 he joined Columbia University, which was then blessed with Leon Lederman, Jack Steinberger, Mel Schwartz, T.D. Lee and I.I. Rabi, and a year later launched on a long, painstaking pro­ gramme of research looking at lepton pairs emerging from particle inter­ actions. The programme started at the DESY electron synchrotron at Hamburg, then moved to the Brookhaven proton synchrotron and now continues at the CERN Intersecting Storage Rings. During this time, Sam Ting has refined to a remarkable extent the experimental techniques which are necessary to sift out leptons from whatever other particle debris is flying around. He has CERN 213.10.76 383 The double arm spectrometer of the MIT/ Brookhaven beam which detected electron- positron pairs coming from the decay of the JI psi particle. The measurement of the decay in the midst of a very high background from other interactions was a triumph of experimental technique. (Photo BNL) ring. Also, during a sabbatical year at CERN in 1975-76, in addition to participating in an ISR experiment, he outlined the physics interest and the design of an electron-positron storage ring with an energy of about 100 GeV per ring. The discovery of J/psi Returning to 1974, the story of the discovery which led to the Nobel Prize awards bears retelling: Sam Ting led a MIT/Brookhaven team looking at collisions between two protons which yielded (amongst many other things) an electron and a positron. The aim was to study some of the electromagnetic features of particles where energy is manifest in the form of a photon which material­ ized in an electron-positron pair. The experiments are not easy to do because the probability that the collisions will been driven by a strong intuition, now Stanford Linear Accelerator Center. yield such a pair is very low. The so abundantly confirmed, that good The construction of SPEAR, under detection system has to be capable of physics is hiding in the study of Burt Richter and John Rees, began in picking out an event from a million particles which materialize into lepton 1970 and was completed, with great or more other types of event. pairs. rapidity and at modest cost, in 1972. It was with long experience of such Burt Richter was born in New York At the same time he led, with Martin problems behind them that the MIT/ in 1931. In 1956 he took his Ph.D. at Perl, Willy Chinowsky, Gerson Gold- Brookhaven team led by Ting, Jean Massachusetts Institute of Technology haber and George Trilling, a Berkeley/ Aubert, Ulrich Becker and Peter Biggs (where he was particularly influenced Stanford team which built a multi­ brought into action a detection system by Francis Friedman) and moved to purpose detection system surrounding with a double arm spectrometer in a Stanford to devote his research life to one of the SPEAR interaction regions. slow ejected proton beam at the electrons since the study of quantum This dual role of storage ring Brookhaven 33 GeV synchrotron in electrodynamics at short distances had builder and experimenter gives him a the Spring of 1974. They used beams caught his imagination. A key point in rare understanding of the physics of 28.5 GeV bombarding a beryllium determining his future career was possibilities with colliding beams. target. involvement with Gerry O'Neil and Like Sam Ting he has been driven by From about August, the realization others from Stanford and Princeton in a strong conviction that the electron- that they were on to something the building of the 300 MeV electron positron system, which does not have important began to grow. The spectro­ storage rings which first collided the complications of colliding hadron meter was totting up an unusually beams in 1965. During the building of systems, is a clean way to extract large number of events where the this machine he sketched, together physics. combined energies of the electron and with Dave Ritson, an outline of a Burt Richter continues to pursue positron were equal to 3.1 GeV. This 3 GeV electron-positron colliding the same path. He is prominent in the is the classic way of spotting a reso­ beam facility which evolved to become experimental programme being pre­ nance. An unstable particle, which the famous SPEAR storage ring at the pared for the Stanford PEP storage breaks up too quickly to be seen itself, 384 The famous magnetic detector of the Berkeley I Stanford team which surrounds one of the intersection regions at the SLAC SPEAR electron-positron storage ring. This detector found the J/psi and several other members of the 'charmonium' family of particles and, this year, has added the discovery of charmed mesons. (Photo SLAC) is identified by adding up the energies of more stable particles which emerge from its decay. The particle decaying into the elec­ tron and positron they were measuring was a difficult one to swallow. The energy region has been scoured before, though not so thoroughly, without anything being seen. Also the resonance was looking 'narrow' — the energy sums were coming out at 3.1 GeV with great precision rather than, for example, spanning from 2.9 to 3.3 GeV. The width is a measure of the stability of the particle and a narrow width means that the particle lives a long time. No other particle of such a heavy mass (over three times the mass of the proton) has anything like that stability. By the end of October, the team had about 500 events from the 3.1 GeV particle and were getting ready to publish their result They baptised it J which is a letter close to the Chinese symbol for 'ting'. The apparition of the same particle apparatus? While meditating in the over the resonance again. The beams at the Stanford Linear Accelerator following months during the transfor­ were nudged from 1.55 to 1.57 and Center was nothing short of shatter­ mation of the storage ring, from everything went crazy. The inter­ ing. Burt Richter described it as 'the SPEAR I to SPEAR II, the gremlin action probability soared higher; from most exciting and frantic week-end in was looked for but not found. It was around 20 nanobarns the cross sec­ particle physics I have ever been then that the suspicion grew that tion jumped to 2000 nanobarns and through'. between 3.1 and 3.2 GeV collision the detector was flooded with events The Berkeley/Stanford team went energies could lie a resonance. producing hadrons. Pief Panofsky, the into action during the week-end During the night of 9-10 Novem­ Director of SLAC, paced around the 9-10 November to check back on ber the hunt began, changing the control room invoking the Deity in some 'funny' readings they had seen beam energies in 0.5 MeV steps. By utter amazement at what was being in June, when cross sections (the 11.00 a.m. Sunday morning the new seen. This heavy particle, displaying probability of an interaction between particle had been unequivocally found. such extraordinary stability, they called an electron and positron occurring) A set of cross section measurements psi and they announced it in a paper were measured with electrons and around 3.1 GeV showed that the beginning with the words 'We have positrons at 1.5, 1.55 and 1.6 and probability of interaction jumped by observed a very sharp peak 1.65 GeV energy in each beam. The a factor of ten from 20 to 200 nano- Within hours of the SPEAR meas­ measurement at 1.6 GeV was a little barns. In a state of euphoria, the urements, the telephone wires across high but 1.55 GeV was even more champagne was cracked open and the Atlantic were humming as informa­ peculiar. In eight runs, six measure­ the team began celebrating an im­ tion, enquiries and rumours were ments agreed with the 1.5 GeV data portant: discovery. exchanged. On the Monday morning while two were higher (one of them While Gerson Goldhaber retired to following the week-end of the disco­ five times higher).
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