Interactions News Wire #28-04
5 May 2004  http://www.interactions.org
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Source: Brookhaven National Laboratory
Content: News Release
Date Issued: 5 May 2004
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NEWS RELEASE
number: 04-46
for release: Wednesday, May 5, 2004
contact: Karen McNulty Walsh, 631 344-8350, kmcnulty@bnl.gov or
Peter Genzer, 631 344-3174, genzer@bnl.gov
writer: Marsha Belford

New Machine Record for Heavy Ion Luminosity at RHIC

UPTON, NY -- The Relativistic Heavy Ion Collider (RHIC) at the U.S.
Department of Energy's Brookhaven National Laboratory has established
a new machine record for heavy ion luminosity, well above its
previous performance. Luminosity is an extremely important measure of
a colliding-beam accelerator's performance.

Exceeding all expectations of the 1,000-plus international physicists
working at RHIC, the record-breaking luminosity, or rate of particle
interactions, was set during the most recent experimental run using
gold ions, which lasted four months, from December 2003 until
April 2004.

"The record luminosity performance is a direct reflection of the
expertise of the designers, builders and operators of RHIC. This
tremendous achievement supports the fact that Brookhaven's
Collider-Accelerator Department ranks with the best accelerator
organizations in the world," said Derek Lowenstein, chair of the
Collider-Accelerator Department (C-AD), which operates a suite of
facilities for accelerator-based experiments hosted by the Laboratory.

Funded by the U.S. Department of Energy's Office of Science and
commissioned in 2000 as the world's highest energy heavy-ion
collider, RHIC has so far run four times, with each period of
operation lasting several months. During three of the four runs,
including the one just completed, two beams of gold ions traveling in
opposite directions at near the speed of light have been smashed into
each other. The goal is to recreate what is called quark-gluon
plasma, an extremely dense state of matter thought to have last
existed microseconds after the Big Bang.

Analyses of data from the earlier runs indicate that RHIC is, indeed,
producing an extremely dense form of matter that has never been seen
before. Whether or not it is the long-sought plasma
of quarks and gluons freed from their confinement within the atomic
nucleus remains to be determined. To make such a determination,
experimenters need as much data on the events coming out of RHIC's
gold-beam collisions as possible. So, the higher the rate of RHIC¹s
particle interactions, the more data coming out of those collisions
to support the quark-gluon plasma search.

Given the record-setting luminosity and its contribution to the run's
success, "RHIC's experiments may nail it this time," says accelerator
physicist Thomas Roser, who is responsible for RHIC operations within
C-AD. "I believe that either quark-gluon plasma will be found to be
there within the expected energy range, or something even more
interesting and unexpected will appear."

Luminosity Explained

In the world of high-energy and nuclear physics, energy and
luminosity are the two major parameters defining the performance of a
colliding-beam system such as in RHIC. The higher the kinetic energy
of the particles and the greater the luminosity of the beam, the
better because of the greater likelihood that unusual events will be
detected and new physics -- such as quark-gluon plasma -- will be
discovered.

Given the relationship between energy and speed, the higher a
particle's speed, the greater its energy, and, just as with most
colliding objects, the greater likelihood that a head-on collision
between two particles will cause them to eject other particles.
Traveling nearly as fast as possible, which is the speed of light,
RHIC's particles each have an energy of 100 billion electron volts
(GeV) per nucleon (proton or neutron) within the gold nucleus. This
equals 200 GeV at the collisions' center of mass, or a total
available energy of 40,000 GeV from all the gold nucleons present.

Instantaneous luminosity is a measure of the number of particle
collisions per second. So, the more particles are packed into a
smaller beam area the better because of the greater likelihood that
particles will collide each second. The more reliably a
high-luminosity collider operates, the more particle interactions
over time it can produce.

In setting the new record, RHIC is now delivering routinely twice the
luminosity called for in its design. As a result of its three gold
runs over the past four years, RHIC has increased its delivered
luminosity per run almost 200-fold. The majority of this improvement,
however, came during the most recent gold run.

Additional information can be found at:
http://www.bnl.gov/bnlweb/pubaf/pr/2004/detail.htm and
http://www.bnl.gov/bnlweb/pubaf/pr/2004/QGP.htm

RHIC operation is funded by the Office of Nuclear Physics within the
Department of Energy's Office of Science.

One of the ten national laboratories overseen and primarily funded by
the Office of Science of the U.S. Department of Energy (DOE),
Brookhaven National Laboratory conducts research in the physical,
biomedical, and environmental sciences, as well as in energy
technologies and national security. Brookhaven Lab also builds and
operates major scientific facilities available to university,
industry and government researchers. Brookhaven is operated and
managed for DOE's Office of Science by Brookhaven Science Associates,
a limited-liability company founded by Stony Brook University, the
largest academic user of Laboratory facilities, and Battelle, a
nonprofit, applied science and technology organization. Visit
Brookhaven Lab's electronic newsroom for links, news archives,
graphics, and more: http://www.bnl.gov/newsroom

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