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.
(de:High Energy and Particle Physics Prize)
== Work ==
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.
Bjorken was also among the first to point
out to the phenomena of jet quenching in heavy
ion collisions in 1982.
Richard Feynman subsequently reformulated
this concept into the parton model, used to
understand the quark composition of hadrons
at high energies. The predictions of Bjorken
scaling were confirmed in the early late 1960s
electroproduction experiments at SLAC, in
which quarks were seen for the first time.
The general idea, with small logarithmic modifications,
is explained in quantum chromodynamics by
"asymptotic freedom".
Bjorken co-authored, with Sidney Drell, a
classic companion volume textbook on relativistic
quantum mechanics and quantum fields.
== Publications ==
=== 
Books ===
J.D. Bjorken, S. Drell (1964). Relativistic
Quantum Mechanics. McGraw-Hill. ISBN 0-07-005493-2.
J.D. Bjorken, S. Drell (1965). Relativistic
Quantum Fields. McGraw-Hill. ISBN 0-07-005494-0.
=== Selected papers ===
J. D. Bjorken (1968). "Current Algebra at
Small Distances", in Proceedings of the International
School of Physics Enrico Fermi Course XLI,
J. Steinberger, ed., Academic Press, New York,
pp. 55–81. Online, SLAC-PUB-338
J.D. Bjorken (1969). "Asymptotic Sum Rules
at Infinite Momentum". Physical Review. 179
(5): 1547–1553. Bibcode:1969PhRv..179.1547B.
doi:10.1103/PhysRev.179.1547.J.D. Bjorken
(1982). "Energy Loss of Energetic Partons
in Quark-Gluon Plasma: Possible Excitation
of High pT Jets in Hadron-Hadron Collisions".
FERMILAB-Pub-82/59-THY.
=== 
Full list of papers ===
INSPIRE-HEP -- Bjorken
== Notes
