Number 113, February 3, 1993 by Phillip F. Schewe and Ben Stein
THE SHAPE OF PARTICLE JETS produced in high-energy proton-antiproton
collisions at Fermilab is determined largely by the radiation of gluons.
Collisions in which the outgoing particles have a large momentum perpendicular
to the beam axis are believed to come about by the scattering of a single
quark inside the proton with a single quark inside the antiproton. The
scattered quarks will then convert some of their energy into new particles;
sometimes the particles emerge in a conelike spray or jet. A study of 100-GeV
jets, the highest-energy jets ever seen in a particle physics experiment,
shows that as expected the likelihood of the scattered quark emitting a
gluon goes up at higher energies and that the shape of the ensuing jet
(the width of the cone) depends on the opening angle between the quark
and gluon. (CDF collaboration; F. Abe et al., 8 Feb. 1993 Physical Review
Letters.)
CARBON NANOTUBES FILLED WITH ATOMIC MATERIAL have been made by a group
of scientists working at NEC Fundamental Laboratories in Japan. P.M. Ajayan
and Sumio Iijima reported that heating nanotubes in the presence of lead
and air destroyed the nanotubes' closed ends and caused molten material
to be drawn inside the tubes. It is not currently known whether the inner
material is pure lead or a compound formed by the mixture of lead and air.
Nonetheless, this technique represents a possible way of making nanometer-scale
electric wires. In addition, the filled nanotubes are likely to offer new
insights into the behavior of matter in confined spaces. (Nature, 28 January
1992).
THE VERY LONG BASELINE ARRAY (VLBA) , consisting of 10 25-m radio dishes
far-flung from Hawaii to the Virgin Islands, will have an angular resolution
of 0.0002 arcseconds, equivalent to that of a 8000-km-wide telescope. The
headquarters for the array (which will be operational in a few months)
is Socorro, New Mexico, home of the Very Large Array. With such good resolution,
astronomers can get a much sharper view of galactic and quasar cores, where
they hope to find something unexpected. Through the use of "phase
referencing," a technique for synchronizing the different telescopes
over longer periods (currently the finite precision of atomic clocks and
atmospheric turbulence conspire to limit synchrony to a few minutes) by
intermittently measuring a nearby reference radio source, astronomers also
expect to be able to study even weakly radio-emitting objects in the Milky
Way. (Science, 22 Jan.)
THE INSTITUTO NAZIONALE DI FISICA NUCLEARE in Italy operates four national
labs. At the Frascati lab a new electron-positron machine, called Daphne,
will be finished by 1995. Daphne will be dedicated to the production of
phi mesons for the purpose of studying the CP-violation phenomenon. The
Gran Sasso National Lab is the world's largest underground physics lab.
It houses the GALLEX solar-neutrino detector, a magnetic monopole detector,
a high-energy muon detector (in coincidence with a cosmic-ray air shower
detector on top of the mountain overhead), and detectors for double beta
decay and for supernova neutrino bursts. At the two other labs, heavy-ion
facilities are being built: a superconducting linear accelerator, ALPI,
at Legnaro and a cyclotron at Catania. ("Physics in Italy" special
issue, Physics World, Jan. 1993.)
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