New Machines Will Help Study Mass PARTICLE PHYSICS

Article excerpt

EVERY time you turn on a light, use an electric motor, or watch television, you benefit from 19th-century research into a basic property of matter - the property of electric charge.

Michael Riordan likes to cite this fact to show why particle physicists are excited about a new study of a basic material property - the study of mass.

"We live in a century whose technologies are heavily dependent on our detailed understanding of the behavior of electric charge ... and its associated field - the electromagnetic field" that constitutes light and radio waves, he says. "Nobody could have anticipated such an outcome ... in the 19th century."

With the particle accelerators, Dr. Riordan says, "we embark on a new voyage to discover the nature and origin of mass, another key property of matter, and to understand its associated field. Who can anticipate what will emerge during the 21st century from the knowledge this epochal voyage will provide?"

A particle physicist himself, Riordan currently is on leave from Stanford University in California to serve as staff scientist for the Universities Research Association Inc. in Washington. The association has contracted with the United States Department of Energy to build one of the 'ships" on which physicists plan to set sail for this "epochal journey."

This is the Superconducting Supercollider (SSC) particle accelerator, under construction near Waxahachie, Texas, about 40 kilometers (25 miles) south of Dallas. The second "ship" may be a comparable machine proposed - but not yet authorized - for the European Laboratory for Particle Physics (CERN) at Geneva. As now planned, these machines would carry physicists' investigations into an energy range where the secrets of this mysterious property called mass should begin to reveal themselves.

Mass is the property that gives rise to gravity and to inertia - the tendency of matter to resist acceleration. It is a familiar property. Yet in spite of the deep insights physicists now have into matter's underlying nature, they do not know why the basic material particles have the particular masses they measure. They cannot even explain how mass itself arises.

The leading speculation suggests that there is a new type of energy-carrying field - called a Higg's field - that exists everywhere. Roughly speaking, the strength with which particles interact with this field determines their resistance to acceleration and, hence, their mass. If one or more such fields exist, they should have one or more new types of particle associated with them. The new accelerators are designed to concentrate enough energy in a small enough volume to create Higg's particles.

The machines would do this by smashing together counter-rotating beams of protons and antiprotons in head-on collisions. Antiprotons and protons share most characteristics except they have opposite charges.

Physicists specify particle energies in these colossal collisions in terms of a unit they call an electron volt (eV). …


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