Number 11, December 3, 1990 by Phillip F. Schewe and Ben Stein
HERA, THE ELECTRON-PROTON COLLIDER in Hamburg, Germany, is now built and will undergo tests. The only machine of its type in the world, HERA (Hadron Elektron Ring Anlage) will send beams of 30-GeV electrons against beams of 820-GeV protons. The electron-proton collisions, which will be observed in two large detectors, called ZEUS and H1, will, like the much lower-energy fixed-target collisions that won Henry Kendall, Jerome Friedman, and Richard Taylor a Nobel Prize in October, probe the inner structure of the proton. (Nature, November 22, 1990.)
LIGHT-FRONT TAMM-DANCOFF (LFTD) theory attempts to describe how particles interact via the strong interaction in a way that avoids various problems that have troubled other theories in recent years. Scientists at the Ohio State University, including Kenneth G. Wilson (614-292-8686) and Robert J. Perry (614-292-6506), begin by using a coordinate system in which light moving in one direction stands still; in other words, the coordinate system moves with light along a "light front." This insures that pairs of virtual particles cannot pop out of the vacuum and go off in opposite directions (an occurrence that plagues normal field theory) because everything is flung backward. A second step involves a "Tamm-Dancoff truncation," named for I. Tamm and S.M. Dancoff, which cuts off the number of possible virtual particles that "mediate" the interaction. Theorists at Ohio State and elsewhere are hoping that in coming years the LFTD approach will help to solve a number of problems in nuclear physics and particle physics. (Upcoming article in Physical Review Letters.)
A PROTON ACCELERATOR FOR CANCER THERAPY was recently installed at the Loma Linda University Medical Center in southern California. The $30-million clinical instrument, a direct descendent of accelerators used in particle physics research, is presently the world's most costly medical machine. Protons--unlike x rays, which do not stop once they reach the tumor--give up their energy mostly at the tumor site, where they help to kill tumor cells, while doing much less damage to surrounding tissue. (Scientific American, December 1990.)
THE CRAF AND CASINI SPACECRAFT , like the Galileo orbiter on its way to Jupiter, have a more complex task than the earlier Voyager planet flyby missions. Casini (named for the 17C Italian astronomer who discovered the gap in Saturn's rings and several of its moons) will orbit Saturn for four years, observing its moons and rings, and will send a probe into Titan's (Saturn's largest moon) atmosphere. It is scheduled for launch in 1996. CRAF (the Comet Rendezvous/Asteroid Flyby), scheduled for launch in 1995, will meet asteroid 449 Hamburga (with a diameter of 53 miles) and then journey near Jupiter to study Comet Kopft. (Astronomy, December 1990.)
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