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James D. Prentice

James D. Prentice (1930-2018)

Jim joined the physics department in 1959 and was the main instigator 
 in starting the particle physics/HEP experimental group in the 1960s. 
 During that decade and into the 1970s the group concentrated on analyzing 
 film from large bubble chamber experiments at Argonne National Laboratory 
 and Fermilab and built up a strong team for scanning and digitizing 
 the track information from the observed particle interactions using 
 PDP computers. The physics emphasis at the time was on finding new 
 particle resonances in the “particle zoo” that was emerging and 
 analyzing their properties. 
 In the 1970s the group’s focus shifted to so-called “counter” experiments, 
 which measured high energy particle interactions using electronic 
 techniques for reading out detectors such as scintillator arrays, 
 spark chambers, wire proportional chambers and Cerenkov counters. Jim 
 and some other group members joined an experiment called the charged 
 and neutral spectrometer at Argonne National Laboratory led by Ohio 
 State University. This experiment focussed on studying particles 
 decaying to photons, which were measured using spark chambers built 
 at Toronto. The group’s work shifted to Fermilab in the mid seventies 
 and Jim was the Toronto leader in a collaboration with groups from the 
 University of California at Santa Barbara and Fermilab that made the 
 first high-energy measurements of the photon total cross-section on 
 the proton and some heavy nuclei.
 After the discovery of the charm quark in 1974, many experiments were 
 mounted at Fermilab to attempt to study its properties. One of the first 
 and arguably best was E531, which included Jim and other Toronto group 
 members, Ohio State University and Nagoya University. This experiment 
 made the first measurements of charmed particle lifetimes by producing 
 the particles in an emulsion target with a neutrino beam. Particle 
 tracks measured in drift chambers built at Toronto were traced back into 
 the processed emulsion for each “event” to find the neutrino interaction 
 vertex and the charmed particle produced, which decayed typically less 
 than a millimetre from the vertex.
 In the 1980s the group moved its activities gradually to Europe. Jim led 
 Toronto into the ARGUS collaboration that was using the DORIS 
 electron-positron collider at the DESY laboratory in Hamburg to 
 produce hadrons with bottom quarks. This experiment was very successful 
 and in particular discovered a surprisingly large mixing of neutral 
 B and anti-B mesons (neutral mesons containing the bottom quark), 
 which indicated that the undiscovered top quark was much heavier than 
 thought at the time. A precision cylindrical vertex chamber was built 
 at Toronto for this experiment. Jim also was involved in the ZEUS 
 collaboration at the HERA electron-proton collider at DESY, which made 
 finely detailed measurements of the inner workings of the proton.  This 
 was his last experiment before retirement in 1994.
 In the late 1960s Jim was involved with a Canadian group who applied to 
 the National Research Council and the Canadian government to make a 
 contribution to the Fermilab laboratory near Chicago, Illinois. This 
 was unsuccessful, but led to the formation of the Institute of Particle 
 Physics, a national organization that coordinated and helped bring 
 together all the Canadian particle physicists to work collaboratively on 
 ever larger projects.  Jim was heavily involved in this process, and 
 eventually served a five-year term as director of IPP from 1976-81.
 His scientific legacy is not just the 220 peer-reviewed articles that he 
 authored and co-authored, but the many students and postdoctoral fellows 
 he trained over his 35-year career at the University of Toronto. - Stephen Julian, Pekka Sinervo and John Martin


Jim Prentice's Career in Nuclear Physics

He, with Henry Caplan and N W Gebbie (Can J Phys 1963 19(30 19-20), did some very fine work using the 4MV Van de Graaff at the old Princess Margaret Hospital on the gamma rays from the nucleus 19F, which at that time was of great interest to the developing collective model of the nucleus. Then when the EN Tandem was to be replaced by the MP Tandem at Chalk River in about 1962, Jim and others tried to get it to be relocated at the University of Toronto, instead of buying an electron Linac. They lost that struggle with Ken McNeill who wanted an electron linear accelerator - the Linac. So the EN tandem instead went to the University of Montreal where it is, I believe, still operating. The ill fated Linac was not viewed by the NRC and AECB committees with much favour and the apparent crisis resulted in Harry Welsh asking me to join the Physics Department. In those days Harry Welsh was persuaded to do so by Professors Lynn Trainor and Bill Sharp from Applied Mathematics.

The idea for IsoTrace was already born by 1961 at Chalk River, so if the tandem had later come to the

U of T and IF I had come also (not likely I expect), the science done here might have been quite different. Who knows what also might have been changed too.  Instead when I came to Toronto I carried on here with the VdG at the PMH with Dick Azuma and students and with students on the Linac. After the Linac closure, IsoTrace was later born at the University of Rochester with my help and that of the U of T students.  Later in 1979 with assistance from Prof D W Strangway of Geology a machine for isoTrace was obtained for the U of T.

- Ted Litherland

Obituary from the Globe and Mail from Saturday January 27, 2018