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The Nobel Prize in Physics was awarded today for the color force contribution to the Standard Model of particle physics
Two American Physical Society members, David Gross of the Kavli Institute at UC Santa Barbara and Frank Wilczek of MIT, shared the 2004 Nobel Prize in physics with H. David Politzer of Caltech for their contributions to the theory describing the forces that hold quarks together.
The Nobel award cites the three "for the discovery of asymptotic freedom in the theory of the strong interaction," also known as the color interaction of quarks, which is a critical cornerstone in the Standard Model of particle physics. The Standard Model is the most complete description of the forces between fundamental particles that is consistent with theories of relativity and quantum mechanics. Fundamental particles include leptons, such as electrons and neutrinos, and hadrons, which are particles made up of quarks. The protons and neutrons in atoms are examples of hadrons.
Unlike gravity and electromagnetic force, which decrease in strength as interacting particles move away from each other, the color force increases as the quarks in hadrons move farther apart, and exerts very little force when the quarks are close together. The asymptotic freedom mentioned in the 2004 Physics Nobel citation refers to the fact that quarks act essentially as free particles when they are near other quarks in a hadron, while the force rises so rapidly as the particles are separated that individual, unbound quarks have not yet been detected. The strong force that holds protons and neutrons together in atoms is a residual effect of the color interaction between quarks.
All three of the papers listed in the Nobel Prize citation were published in APS journals in 1973. Two of the papers, one by Politzer and the other by Gross and Wilczek, appeared back to back in Physical Review Letters (PRL) on June 25, 1973. The third paper, by Gross and Wilczek, was published in Physical Review D (PRD) in November of the same year. "We are particularly pleased that the full theory of asymptotic freedom was laid out in PRD," says APS Editor in Chief Martin Blume. "PRL is our premier journal for brief accounts of important work with broad interest in the physics community. PRD is the premier journal of particle physics and related topics, where detailed reports are published. The PRD paper was the first complete publication of the 2004 Nobel work, and led to literally hundreds of subsequent papers and a burst of theoretical and experimental progress."
"We are very proud that two of the winners of the 2004 physics Nobel prize, Gross and Wilczek, are members of the American Physical Society," says Judy Franz, APS Executive Officer. "The contribution of Gross, Politzer, and Wilczek was a groundbreaking discovery that rapidly convinced people that quantum chromodynamics provided a true understanding of strong interactions. Their work created an explosion of interest, and made possible entirely unexpected advances in the Standard Model. The APS wholeheartedly supports the recognition of the work of Gross, Politzer, and Wilczek. In fact, the APS presented its prestigious J. J. Sakurai Prize for Theoretical Particle Physics to them in 1986, anticipating the Nobel committee's decision by18 years."
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The American Physical Society is a nonprofit membership organization working to advance and diffuse the knowledge of physics through its outstanding research journals, scientific meetings, and education, outreach, advocacy, and international activities. APS represents over 55,000 members, including physicists in academia, national laboratories, and industry in the United States and throughout the world. Society offices are located in College Park, MD (Headquarters), Ridge, NY, and Washington, D.C.