Vernon Hughes

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Vernon Willard Hughes (born May 28, 1921 in Kankakee , Illinois , † March 25, 2003 in New Haven , Connecticut ) was an American experimental physicist who dealt with atomic and particle physics and was known for his precision measurements.

Life

Hughes studied at Columbia University (bachelor's degree in 1941), where he received his doctorate in 1950 with Isidor Isaac Rabi (who named him one of his best students) and was a lecturer from 1949 to 1952. Before that he was involved in radar development at the Radiation Laboratory of the Massachusetts Institute of Technology during World War II , for example in the construction of precise clocks. From 1952 to 1954 he was an assistant professor at the University of Pennsylvania . From 1954 (as Assistant Professor ) until his retirement in 1991 he was Professor at Yale University , from 1969 as Donner Professor and from 1978 as Sterling Professor .

From 1961 to 1969 he headed the physics faculty on the recommendation of Robert Oppenheimer . In 1984 he was I. I. Rabi visiting professor at Columbia University.

He received the 1978 Davisson-Germer Prize in Atomic Physics and in 1990 the Tom W. Bonner Prize in Nuclear Physics . In 1961 he was elected to the American Academy of Arts and Sciences . He had been a member of the National Academy of Sciences since 1967 and was an honorary doctor from Heidelberg University .

He was married twice and had two sons from his first marriage (1950) to the German emigrant Inge Michaelson, who died in 1979. His son Emlyn Hughes is a physics professor at Caltech and continued his father's high-energy experiments with polarized electrons at SLAC.

plant

In his dissertation, he and Lou Grabner dealt with the electromagnetic interaction with nuclear quadrupole moments, which led to the first observation of a two-photon transition. In the 1950s he studied, among other things, the positronium (shortly after its discovery by Martin Deutsch ) and the helium atom, on which he carried out precision measurements until the 1980s, among other things to test quantum electrodynamics and to precisely determine the fine structure constant. In 1960 he was the first to investigate muonic atoms ( muonium ), on which he carried out precision measurements for decades, for example at the LAMPF meson factory of the Los Alamos National Laboratory . Hughes himself developed ideas for such a meson factory (a proton linear accelerator, also for the production of muons) in Yale in 1958, but they were not implemented there.

In 1960 he carried out precise direction-dependent measurements of the inertial mass of the proton to test Mach's principle ( they found no deviations with a relative accuracy of ). Also in the 1950s he determined the charge difference between electrons and protons and upper limits for the neutron charge with high accuracy.

From 1959 he was also a pioneer at SLAC in the use of polarized electrons (and muons) in high-energy accelerators, which enabled spin-sensitive structural investigations, for example of the proton, which Hughes carried out from 1972 in deep inelastic scattering experiments at CERN , which later became part of the European Muon Collaboration (EMC) of CERN were continued by him. It turned out that a much smaller portion of the spin than expected was carried by the quarks ( spin crisis ) and from 1987 Hughes was given the opportunity to investigate this more closely in the Spin Muon Collaboration at CERN, of which he was the spokesman (she collected from 1992 to 1996 data). Also with such polarization experiments, Hughes and co-workers demonstrated the parity violation in deep inelastic electron scattering on nucleons and, at low energy, in elastic electron scattering on carbon nuclei.

Most recently he carried out (with plans from 1982) at Brookhaven National Laboratory precision measurements of the anomalous magnetic moment (g-2 factor) of the muon, with significantly higher accuracy than before at CERN (in the end with a relative accuracy in the billionth range). The determination of the (g-2) factor of the muon is a precision test of the Standard Model . The theoretical predictions, however, contain a part (loops with hadrons ), which in turn can only be determined through experiments. The results, first published in 2001, did not agree with the best theoretical calculations in 2007 (with a difference of more than three standard deviations), which, according to some physicists, is an indication of a necessary extension of the Standard Model (for example through supersymmetry ).

Fonts

  • Muonium . In: Annual Review Nuclear Science , Volume 16, 1966, pp. 445-470

literature

  • Robert K. Adair: Obituary. In: Biographical Memoirs of the National Academy of Sciences .

Web links

Individual evidence

  1. ↑ The book Waveforms with Burton Chance and others emerged from the work after the war (MIT Radiation Laboratory, McGraw Hill 1949)
  2. ↑ Grabner, Hughes. In: Physical Review , Volume 82, 1951, p. 561
  3. ↑ Hughes, McColm, Ziock, Prepost: Formation of Muonium and Observation of its Larmor precession . In: Physical Review Letters , Volume 5, 1960, p. 63
  4. ↑ Hughes, Robinson, Beltran-Lopez. In: Physical Review Letters , Volume 4, 1960, p. 342
  5. ↑ Physical Review , Volume 105, 1957, p. 170
  6. ↑ Hughes et al. a. In: Physical Review Letters , Volume 65, 1990, p. 694
  7. ^ GW Bennett, Hughes et al. a .: Final Report, Brookhaven . In: Physical Review , D, Volume 73, 2006, arxiv : hep-ex / 0602035 . Further improvements to the experiment would have been possible in a sequel, but were not made for reasons of cost.
  8. ^ Hagiwara, Martin, Nomura, Teubner: Improved prediction for g-2 of the muon . In: Physics Letters , B, Volume 649, 2007, p. 173, arxiv : hep-ph / 0611102
personal data
SURNAME Hughes, Vernon
ALTERNATIVE NAMES Hughes, Vernon Willard (full name)
BRIEF DESCRIPTION American experimental physicist
DATE OF BIRTH May 28, 1921
PLACE OF BIRTH Kankakee , Illinois
DATE OF DEATH March 25, 2003
Place of death New Haven , Connecticut