Number 166, February 25, 1994 by Phillip F. Schewe and Ben Stein
METASTABLE ANTIPROTONIC HELIUM ATOMS are made by shooting beams of antiprotons
into liquid helium. Experiments at the KEK lab in Japan in 1991 showed
that the annihilation of some antiprotons was greatly delayed (from an
expected lifetime of picoseconds to an observed interval as long as microseconds),
suggesting the creation of a metastable state. The same scientists, in
collaboration with physicists from Germany and Hungary, have now performed
the first laser spectroscopy studies of these exotic atoms. They conclude
that the longevity of the antiprotons in helium results from the formation
of a neutral atom consisting of an antiproton and a helium ion. The researchers
deduce that the observed emissions at a wavelength of 597 nm correspond
to the transition from one high-energy, high-orbital- momentum state (n=39,
l=35) to another (n=38, l=34). (N. Morita et al., 21 Feb. 1994, Physical
Review Letters.)
ARE ELLIPTICAL GALAXIES BORN IN THE COLLISIONS OF SPIRAL GALAXIES? The
main argument against this hypothesis is the fact that globular clusters
are more numerous in ellipticals than in spirals. One would have thought
that some of the globulars would be lost in the collision and that they
would therefore be less prevalent in ellipticals. Recent Hubble Space Telescope
pictures of colliding spirals suggest, however, that new globular clusters
may be formed in the collision process, notwithstanding the tendency (at
least in our galaxy) for globular clusters to be extremely old structures.
According to M.G. Edmunds of the University of Wales, the demonstration
that new globular clusters were being formed would buttress the view that
ellipticals and possibly other astrophysical objects are created out of
collisions. (Nature, 10 Feb. 1994.)
PARTICLE PHYSICS WITHOUT THE SSC was the subject of SLAC director Burton
Richter's talk at this week's meeting of the AAAS in San Francisco. Richter
said that it was inevitable that the field would suffer a shrinkage in
the number of graduate students but that there were still several labs---LEP,
HERA, Tevatron, etc.---and plenty of topics of interest---e.g., the top
quark, CP violation, deep inelastic scattering as a probe of the proton's
interior---to keep particle physics alive. As for the need for more powerful
accelerators, Richter suggested a scenario in which Europe would build
the next proton machine (the 14-TeV Large Hadron Collider) while Japan
and the U.S. would together build an electron-positron collider, a 0.5-1.5
TeV machine usually referred to generically as the Next Linear Collider
(NLC). The SSC had been a badly-managed project, Richter asserted. Before
attempting any such large project again, he said, a carefully prepared
consensus on goals and expectations (and costs) would have to be reached
among scientists, Congress, federal agency officials, and any prospective
foreign collaborators.
OBSERVATIONS OF SUPERCONDUCTIVITY AT 250 K are difficult to confirm
for a number of reasons. For one thing, the samples used by Michel Lagues
in Paris were painstakingly made atomic layer by layer, the better to control
the structure, and are therefore quite small, only 5 x 10**-8 cu.cm. This
complicates the task of making electrical contact, which limits the sensitivity
of resistance measurements. Other problems are stability and reproducibility;
similar samples don't act alike and don't retain fixed properties for more
than a few days. (Physics Today, Feb. 1994.)
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