A Schematic Model of Baryons and Mesons, in Physics Letters, 8, Number 3, 1 February 1964, pp. 214-215

FIRST EDITION OF MURRAY GELL-MANN'S SEMINAL PAPER POSITING THE IDEA OF ‘QUARKS' INSIDE THE ATOMIC NUCLEUS. Bound full volume. Gell-Mann took nearly a year to write this short, Nobel Prize winning paper, and yet in it, three quarks later named ‘up,' ‘down,' and ‘strange' "explained phenomena that theorists had been puzzling over for years" (Crease, The Second Creation, 283).

"A landmark in contemporary physics, the eight-paragraph note is a model of scientific prose: brief, logical, achingly clear, so tightly and modestly drawn that its full scope may elude the reader. In the first line, the author sets forth his intention: "If we assume that the strong interactions of baryons and mesons are correctly described in terms of the broken eightfold way, we are tempted to look for some fundamental explanation of the situation."

And then he did just that. Gell-Mann's paper "explained how various combinations of three particles from a triplet could produce baryons (such as protons and neutrons), while two members from the triplet could combine to form a meson (the most famous example at the time being the pi meson, or pion). Maintaining standard electric charges required a fourth particle for this approach to work, Gell-Mann noted in his paper. But "a simpler and more elegant scheme can be constructed if we allow non-integral values for the charges," he wrote. "We then refer to the members ... of the triplet as ‘quarks.'"

Gell-Mann "proposed the quark hypothesis to account for the explosion of subatomic particles discovered in accelerator and cosmicray experiments during the 1950s and early 1960s. Over a hundred new particles, most of them strongly interacting and very short-lived, had been observed. These particles, called hadrons, are not elementary; they possess a definite size and internal structure, and most can be transformed from one state into another.

"The quark hypothesis suggested that different combinations of three quarks—the up (u), down (d), and strange (s) quarks—and their antiparticles could account for all of the hadrons then known. Each quark has an intrinsic spin of 1/2 unit and is presumed to be elementary, like the electron. So far, quarks appear to have no size or internal structure and thus represent the smallest known constituents of matter. To explain the observed spectrum of hadrons, quarks had to have electric charges that are fractions of the electron charge. The u quark has charge 2/3 while the d and s quarks have charges 1/3 (in units where the electron charge is 1).

"The observed hadron spectrum agreed remarkably well with the expected states formed from combinations of three quarks or a quark-antiquark pair. Quarks also seemed to form a counterpart to the other class of elementary particles, the leptons, which then included the electron (e) and muon (µ) (both with unit charge) and their companion chargeless neutrinos, e and µ. The leptons do not feel the strong interaction, but they do participate in the electromagnetic interactions and the weak interaction responsible for radioactive decays. They have the same spin as the quarks and also have no discernible size or internal structure" (Carithers & Grannis, SLAC: Discovery of the Top Quark, 6).

In 1969, Gell-Mann was awarded the Nobel Prize in Physics "for his contributions and discoveries concerning the classification of elementary particles and their interactions" (Nobel Media). CONDITION & DETAILS: Complete volume containing Vol. 8, Nos 1-5 (Jan.-March, 1964). Amsterdam: North-Holland Publishing Company, 1964. Ex-libris bookplate and pocket from General Electric General Engineering Laboratory. Quarto, full brown cloth library binding. Slight scuffing at the foot of the spine; gilt-lettered at the spine. Fine.