Number 116, March 3, 1993 by Phillip F. Schewe and Ben Stein
NEW MEASUREMENTS OF CP-VIOLATION , performed in an experiment which monitors
the way K-zero mesons transform into their own antiparticles (a process
also called mixing), have reached a level of precision twice as good as
that of previous experiments. The failure of interactions to be invariant
under the combined operations of charge conjugation (C) and parity inversion
(P) was first discovered in an early K-zero experiment in 1964. Since then
particle physicists have sought in vain for additional manifestations of
CP violation. Some scientists, suspecting that B mesons may exhibit the
phenomenon, hope to build colliders dedicated to producing B mesons. But
this could be years away, and so K-zero mixing remains the best physical
system for studying CP violation, which continues to be of interest to
theorists because it has a bearing on the asymmetry between matter and
antimatter in the universe and because it has not fully been accounted
for by the so-called Standard Model. The new experiment (L.K. Gibbons,
1 Mar. 1993 Physical Review Letters), carried out at Fermilab by a Chicago-Elmhurst-Fermilab-Princeton-Saclay
collaboration, measured a variety of K-zero parameters. CP violation was
observed to occur in the mixing of K-zeros but not in their decays. The
experiment also served to further verify the invariance of CPT, the compound
operation involving CP and the operation of time reversal (T).
GEMINGA'S PROPER MOTION has been measured. Geminga is a pulsar that
emits almost all its energy at gamma wavelengths. Its x-ray emission is
weaker by a factor of 1000 and its optical emission---if the identification
of an object called G'' as Geminga's optical counterpart is correct---is
2 million times less than the gamma; it seems to emit no radio at all.
Italian astronomers at the Universities of Milan and Cassino have now reanalyzed
optical images recorded over the period 1984-92 and have determined that
Geminga moves across the sky at a rate of 0.17 arcsec/year and that its
distance from Earth is about 300 light years (G.F. Bignami et al., Nature
25 Feb. 1993.) In the following article in the same issue of Nature, Neil
Gehrels and Wan Chen of NASA/Goddard suggest that the supernova that created
Geminga also created the "Local Bubble," the hot, low-density
region of interstellar space containing our solar system. Taking into account
Geminga's velocity and dating the presumed supernova (about 340,000 years
ago) with Gamma Ray Observatory data on the slowing of Geminga's spin rate,
Gehrels and Chen conclude that the supernova might have been in the right
place to clear away the gas in our vicinity, leaving behind the bubble.
(Science News, 2 Jan. 1993.)
PRINCETON'S INSTITUTE FOR ADVANCED STUDY had the highest rate (17.47)
of citations per published paper in the physical-science area---including
physics, chemistry, geoscience, astrophysics, and math---over the period
1981-91, according to the Institute of Scientific Information (ISI). The
next four institutions in order were Xerox, AT&T, Harvard, and Princeton
University. The Institute for Advanced Study fared so well because it has
several prominent authors of frequently-cited papers, including Edward
Witten, Frank Wilczek, and John Bahcall. In terms of total papers over
the decade, the leading institutions in order were AT&T (10,340 papers),
Caltech (including JPL), IBM, Harvard, and Princeton. (Science Watch, Feb.
1993.)
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