Bjorken scaling
| James Bjorken | |
|---|---|
 |
|
| Born |
June 22, 1934 Chicago, Illinois, United States |
| Nationality | American |
| Fields | Theoretical physics |
| Institutions | Fermilab, SLAC |
| Alma mater |
MIT (B.S., 1956) Stanford University (Ph.D., 1959) |
| Doctoral students |
Davison Soper Helen Quinn |
| Known for | Bjorken scaling, Co-predicting the charm quark |
| Notable awards |
Putnam Fellow (1954) Heineman Prize (1972) E. O. Lawrence Award (1977) Pomeranchuk Prize (2000) ICTP Dirac Medal (2004) Wolf Prize in Physics (2015) European Physical Society High Energy and Particle Physics Prize (2015) |
James Daniel "BJ" Bjorken (born 1934) is an American theoretical physicist. He was a Putnam Fellow in 1954, received a BS in physics from MIT in 1956, and obtained his PhD from Stanford University in 1959. He was a visiting scholar at the Institute for Advanced Study in the fall of 1962. Bjorken is Emeritus Professor at the Stanford Linear Accelerator Center, and was a member of the Theory Department of the Fermi National Accelerator Laboratory (1979–1989).
He was awarded the Dirac Medal of the ICTP in 2004; and, in 2015, the Wolf Prize in Physics and the EPS High energy and particle physics prize. ()
Bjorken discovered in 1968 what is known as light-cone scaling, (or Bjorken scaling) a phenomenon in the deep inelastic scattering of light on strongly interacting particles, known as hadrons (such as protons and neutrons): Experimentally observed hadrons behave as collections of virtually independent point-like constituents, when probed at high energies.
Properties of these hadrons scale, that is, they are determined not by the absolute energy of an experiment, but, instead, by dimensionless kinematic quantities, such as a scattering angle or the ratio of the energy to a momentum transfer. Because increasing energy implies potentially improved spatial resolution, scaling implies independence of the absolute resolution scale, and hence effectively point-like substructure.
This observation was critical to the recognition of quarks as actual elementary particles (rather than just convenient theoretical constructs), and led to the theory of strong interactions known as quantum chromodynamics, where it was understood in terms of the asymptotic freedom property. In Bjorken's picture, the quarks become point-like, observable objects at very short distances (high energies), shorter than the size of the hadrons.
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