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University of Chicago

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PHYSICS NEWS UPDATE
A digest of physics news items prepared by Phillip F. Schewe, AIP
Public Information
Number 93   September 9, 1992

AND NOW, A COSMIC-RAY NEUTRINO PROBLEM.  When
cosmic rays collide with air molecules in the upper atmosphere,
they create neutrinos.  Experiments at Japan's Kamiokande
neutrino detector and a similar setup in a salt mine near
Cleveland, however, have found that the proportion of muon
neutrinos to electron neutrinos produced from cosmic rays is
significantly smaller than the Standard Model predicts.  One
possibility is that physicists have miscalculated the amount of
muon neutrinos that should be produced in the upper atmosphere. 
Other explanations, however, involve new physics.  One possibility
is that the muon neutrinos transform into another type of neutrino
on their way to Earth.  Such neutrino oscillations have been
offered as an explanation for the apparent shortfall of electron
neutrinos from the Sun.  Indeed, electron and muon neutrinos may
be in some kind of equilibrium, according to Thomas Gaisser of
the University of Delaware.  (Science, 22 August 1992.)  

DOUBTS ABOUT A 17-KEV NEUTRINO are growing. 
Scientists at last month's International High Energy Physics
meeting in Dallas discussed the results of the latest round of
experiments seeking to confirm the existence of a 17-keV neutrino. 
All of them came up short.  Eric Norman of LBL, using a
solid-state detector, found positive signs for the 17-keV neutrino
in the beta-decay of carbon-14, but not in iron-55.  Takayoshi
Oshima of the National Laboratory for High Energy Physics in
Japan looked for evidence of the neutrino in the most sensitive
mass spectrometer test designed yet, and found nothing.  Finally,
Stuart Freedman of LBL studied beta-decay of radioactive sulfur
using a solid-state detector, and did not see any signs of the
neutrino.  Freedman went so far as to test the sensitivity of his
detector by mixing in some carbon-14, which produces beta-decay
electrons at slightly lower energies than in sulfur, and managed to
produce a signal mimicking the 17-keV spike.  Although the
prospect of a superheavy neutrino now appears dead, physicists are
still at a loss to explain why positive signals had previously shown
up in six independent solid-state detector experiments.  (Science,
22 August 1992.)  

THE SMALLEST BATTERY consists of two pillars of silver
atoms and two of copper, assembled by STM on a graphite
substrate (August 6 issue of the Journal of Physical Chemistry). 
The battery arrangement generates about one-fiftieth of a volt and
lasts about 45 minutes.  Over that time, the copper pillars shrink
while the copper atoms migrate to the silver pillars.  One of the
Irvine scientists, Reginald Penner, hopes to use the device to study
proteins.  (Science News, 15 August 1992.)

THE PLUTO FAST FLYBY mission, under consideration at
NASA, would shoot a pair of light spacecraft (150 kg compared to
1500 kg for Galileo) toward Pluto aboard a Titan/Centaur rocket. 
If approved, the craft would depart as early as 1998 and take seven
or eight years to reach the ninth planet, where they would take
pictures and perform spectroscopy at radio, infrared, and
ultraviolet wavelengths.  (Nature, 27 August 1992.)