PHYSICS NEWS UPDATE A digest of physics news items prepared by Phillip F. Schewe, AIP Publ

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PHYSICS NEWS UPDATE A digest of physics news items prepared by Phillip F. Schewe, AIP Public Information Number 166 February 25, 1994 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 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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