Quark finders win Nobel.

Quark finders win Nobel

This year's Nobel Prize in Physics honors three researchers whose work demonstrated the existence of the quark, a subatomic particle that is one of the basic building blocks of matter. The Royal Swedish Academy of Sciences awarded the prize last week to Richard E. Taylor of Stanford University and to Jerome I. Friedman and Henry W. Kendall of the Massachusetts Institute of Technology.

The trio studied results from "deep inelastic scattering" experiments conducted at the Stanford Linear Accelerator Center from 1967 to 1973. Electrons were accelerated along a 2-mile-long tube to an energy of 20 billion electron-volts and then smashed into samples of liquid hydrogen or deuterium so violently that their protons or neutrons shattered. Two magnetic spectrometers recorded the electrons' postcollision energy and direction.

To the physicists' surprise, electron-scattering patterns indicated that a large number of electrons were ricocheting at large angles, as if they had struck hard, point-like objects inside the protons and neutrons. The scientists gradually realized that this discovery "was going to change the way people looked at subatomic particles," Friedman told SCIENCE NEWS. The results furnished the first experimental evidence that protons and neutrons, once believed indivisible, are made up of quarks--elementary particles with fractional charges of +2/3 or -1/3.

The research confirmed the 1964 proposal of quarks' existence by George Zweig and Nobel laureate Murray Gell-Mann, two theorists at the California Institute of Technology in Pasadena. For years, physicists thought of quarks only as "mathematical entities," Friedman says, because they had failed to find these particles anywhere -- whether searching in seawater, meteorites or high-energy particle accelerators.