James Daniel "BJ" Bjorken (born 1934) is one of the world's foremost theoretical physicists. He was a Putnam Fellow in 1954, received a BS in physics from MIT in 1956, and obtained his PhD from Stanford University

Stanford University

The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...

 in 1959. He is Emeritus Professor at the Stanford Linear Accelerator Center

Stanford Linear Accelerator Center

The SLAC National Accelerator Laboratory, originally named Stanford Linear Accelerator Center, is a United States Department of Energy National Laboratory operated by Stanford University under the programmatic direction of the U.S...

, and was a member of the Theory Department of the Fermi National Accelerator Laboratory (1979–1989).

Bjorken discovered what is known as light-cone scaling, (or "Bjorken scaling") a phenomenon in the deep inelastic scattering

Deep Inelastic Scattering

Deep inelastic scattering is the name given to a process used to probe the insides of hadrons , using electrons, muons and neutrinos. It provided the first convincing evidence of the reality of quarks, which up until that point had been considered by many to be a purely mathematical phenomenon...

 of light on strongly interacting

Strong interaction

In particle physics, the strong interaction is one of the four fundamental interactions of nature, the others being electromagnetism, the weak interaction and gravitation. As with the other fundamental interactions, it is a non-contact force...

 particles, known as hadron

Hadron

In particle physics, a hadron is a composite particle made of quarks held together by the strong force...

s (such as proton

Proton

The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

s and neutron

Neutron

The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...

s). This was critical to the recognition of quark

Quark

A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly...

s as actual elementary particle

Elementary particle

In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which...

s (rather than just convenient theoretical constructs), and led to the theory of strong interaction

Strong interaction

In particle physics, the strong interaction is one of the four fundamental interactions of nature, the others being electromagnetism, the weak interaction and gravitation. As with the other fundamental interactions, it is a non-contact force...

s known as quantum chromodynamics

Quantum chromodynamics

In theoretical physics, quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons . It is the study of the SU Yang–Mills theory of color-charged fermions...

. In Bjorken's picture, the quarks become point-like, observable objects at very short distances (high energies).

Richard Feynman

Richard Feynman

Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics...

 subsequently reformulated this concept into the parton model

Parton (particle physics)

In particle physics, the parton model was proposed by Richard Feynman in 1969 as a way to analyze high-energy hadron collisions. It was later recognized that partons describe the same objects now more commonly referred to as quarks and gluons...

, 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

Asymptotic freedom

In physics, asymptotic freedom is a property of some gauge theories that causes interactions between particles to become arbitrarily weak at energy scales that become arbitrarily large, or, equivalently, at length scales that become arbitrarily small .Asymptotic freedom is a feature of quantum...

".

Bjorken co-authored, with Sidney Drell

Sidney Drell

Sidney David Drell is an American theoretical physicist and arms control expert. He is a professor emeritus at the Stanford Linear Accelerator Center and a senior fellow at Stanford University's Hoover Institution. Drell is a noted contributor in the field of quantum electrodynamics and particle...

, a classic companion volume textbook on relativistic quantum mechanics and quantum fields that is still used by many practicing particle physicists.

Papers