From: revu@ellis.uchicago.edu (Sendhil Revuluri)
Newsgroups: sci.physics
Subject: Physics News Update #91 (8/12)
Summary: First posting of PNUP to sci.physics
Keywords: physics news interesting banana
Date: 14 Aug 92 19:33:26 GMT
Article-I.D.: midway.1992Aug14.193326.19268
Reply-To: revu@midway.uchicago.edu
Distribution: usa
Organization: University of Chicago

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In response to the requests for "real" physics information, I am going
to post this and future "Physics News Updates" distributed by AIP
Public Information's Phillip Schewe to sci.physics.  (Sorry for the
delay; it took me this long to get permission, etc.)  For those who
want to receive PNUPs via email, mail pfs2@aip.org with your address
and you will be added to the distribution list.

Complaints or suggestions are welcome; please mail them to me at the
address below.


Sendhil Revuluri (s-revuluri@uchicago.edu)
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 91   August 12, 1992

MEASUREMENTS OF MULTI-JET PRODUCTION RATES in
deep inelastic muon-proton scattering support the theory of
quantum chromodynamics (QCD).  Stealing a march on HERA---
the electron-proton collider in Hamburg, where proton-lepton
(electrons instead of muons) scattering will be the exclusive
concern---scientists at Fermilab (contact: Jorge Morfin, 708-840-
4561) have studied what happens when a beam of 490-GeV muons
is smashed into a stationary hydrogen target.  Quite often the
muon can be thought of as scattering not from the proton as a
whole but from individual quarks within the proton.  Some of
these quark-muon interactions will be highly inelastic; that is,
much of the collision energy will be converted into new particles,
some of which emerge from the collision vertex in jets.  QCD
holds that in certain reactions, gluons (the carriers of the strong
nuclear force between quarks) may also spawn jets through a sort
of radiative process, much like photon bremsstrahlung.  Fermilab
has not only seen such multi-jet (in particular, 3-jet) events, but
has for the first time measured their rate of production, a value
which agrees with the QCD prediction.  (M.R. Adams et al., 17
August issue of Physical Review Letters.)

THE FIRST EXTRAGALACTIC GAMMA RAYS in the TeV
energy range have been observed by a group of astronomers at the
Whipple Observatory in Arizona. The gamma source, the galaxy
Markarian 421 (400 million light years away), had previously been
seen at radio, visible, and x-ray wavelengths, and at gamma
energies into the GeV range by the Gamma Ray Observatory. The
Whipple measurements, made with Cerenkov counters that detect
showers engendered by the gammas hitting our atmosphere, show
that the gamma flux from Mk421 is only a factor of three lower
than that of the Crab Nebula (which, sitting in our own galaxy,
serves as the standard candle for TeV gammas) even though it is
100,000 times further away. Mk421 is considered to be a "blaser,"
a category of active galaxy---possibly containing a black hole---that
emits light strongly across the whole electromagnetic spectrum. 
(Nature, 6 August.)

BUCKYBALL CRYSTALS HAVE DIELECTRIC PROPERTIES
that require the existence of a permanent, non-symmetrical
distribution of electric charge in the material at lower
temperatures.  Below 260 K, C-60 crystals undergo a phase change
in which the lattice structure changes and the individual molecules
assume a fixed orientation instead of rotating freely in the lattice. 
Theorists previously believed that the molecules in the low
temperature phase were oriented in such a way as to ensure a zero
electric dipole.  However, Glenn B. Alers and Brage Golding (517-
355-9708) of Michigan State University and their co-workers at
AT&T Bell Labs found that single C-60 crystals subjected to low-
frequency electric fields exhibited a dielectric response containing
frequency-dependent contributions that require the existence of
permanent dipoles in the material.  The researchers propose that
the dipoles are induced by misoriented C-60 molecules which
maintain their own spherical symmetries but break the charge
symmetry of the lattice.  These imperfections in the C-60 lattice
would have implications for the optical and nonlinear properties
of buckyball films, and may mean that the crystal can interact with
a wider variety of electromagnetic frequencies than previously
thought.  (Science, 24 July 1992).

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-- 

Sendhil Revuluri (s-revuluri@uchicago.edu)
University of Chicago
Newsgroups: sci.physics