[Brahms-l] Physics News Update 669 (fwd)

Hi

It seems that BRAHMS (and it's "new" spokesperson) made it to the 
general physics updates. 

Cheers
   Peter

---------- Forwarded message ----------
Date: Wed, 14 Jan 2004 14:56:55 -0500
From: physnews@aip.org
To: pchristi@nbi.dk
Subject: Physics News Update 669

PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 669 January 14, 2004   by Phillip F. Schewe, Ben Stein, and
James Riordon
	
SUPERSOLID, QUANTUM CRYSTAL, A BOSE-EINSTEIN CONDENSATE IN SOLID
FORM---all of these expressions apply to a weird substance observed
bla bla bla

COLOR GLASS CONDENSATE (CGC) is the name for an extreme form of
nuclear matter that may have been created in recent experiments at
Brookhaven's Relativistic Heavy Ion Collider (RHIC).  At this week's
Quark Matter 2004 conference in Oakland, California,
experimentalists presented possible preliminary evidence for this
novel state of matter.  While nuclear physicists are debating the
evidence for a CGC, the concept itself is an accepted, if evolving,
theoretical idea that may describe a universal form of matter at
high energies. In RHIC experiments, researchers ordinarily collide a
beam of gold ions with another beam of gold ions. But during the
first quarter of 2003, they studied the collision of gold ions with
deuterons, nuclei which each consist of a proton and neutron. They
used a deuteron beam precisely to avoid making the coveted
quark-gluon plasma (QGP), the hypothetical soup of individual quarks
and gluons that the RHIC researchers hope to recreate in their
future experiments. They do this in order to better observe the CGC
state, which many believe would be a precursor to QGP
So what is a color glass condensate?  According to Einstein's
special theory of relativity, when a nucleus travels at near-light
(relativistic) speed, it flattens like a pancake in its direction of
motion.  Also, the high energy of an accelerated nucleus may cause
it to spawn a large number of gluons, the particles that hold
together its quarks.  These factors--relativistic effects and the
proliferation of gluons--may transform a spherelike nucleus into a
flattened "wall" made mostly of gluons.  This wall, 50-1000 times
more dense than ordinary nuclei, is the CGC (see
www.bnl.gov/bnlweb/pubaf/pr/2003/colorglasscondensate-background.htm
for a letter-by-letter explanation of the CGC's name).  How does the
gluon glass relate to the much sought quark-gluon plasma?  The QGP
might get formed when two CGC's collide.
Reporting their gold-deuteron data at the Quark Matter conference,
researchers in the BRAHMS collaboration (Jens Jorgen Gaardhoje,
gardhoje@nbi.dk) observed fewer-than-usual high-momentum particles
emitted transverse (sideways) to the direction of the collision.
According to Gaardhoje, the data, which includes BRAHMS's ability to
detect particles at small angles to the beam, provided evidence that
the deuteron nucleus formed a CGC. Meanwhile, the PHOBOS
collaboration (Gunther Roland, MIT, gunter.roland@cern.ch) confirms
the experimental effect seem by BRAHMS, though Roland cautions that
direct calculations that confront the CGC theory with the observed
effect need to be performed.  According to Brookhaven theorist Larry
McLerran (mclerran@quark.phy.bnl.gov), the BRAHMS and PHOBOS
observations provide evidence for this new state of matter.
However, Columbia theorist Miklos Gyulassy
(gyulassy@mail-cunuke.phys.columbia.edu), disagrees. BRAHMS
spokesperson Gaardhoje points out there are conflicting theoretical
views, but considers the suppressed production of high-momentum
particles to be "a necessary feature" of a CGC.  Whether it is
sufficient evidence is another story, he says, and the next RHIC
runs should provide further insights.  Nonetheless, Gyulassy
believes that CGC is a valid concept and that the RHIC researchers
should actively search for signs of it, just as they continue to try
to create and study the QGP (which, incidentally, he believes RHIC
has already produced--see Update 642). (Gaardhoje adds that evidence
for the existence of a CGC state has already appeared in
electron-positron collisions at HERA in Germany.) According to
McLerran, the CGC has the potential to explain many things in
high-energy nuclear physics such as the mechanisms by which
particles are produced in nuclear collisions as well as the
distribution of gluons inside nuclei.  (For more information, see
Brookhaven news release at
www.bnl.gov/bnlweb/pubaf/pr/2003/bnlpr122203.htm )

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