C o l u m b i a U n i v e r s i t y RECORD
September 26, 2003
12
William Zajc and Columbia Scientists Help to Discover Hottest, Densest Matter
BY MICHAEL LAKRIN
C
olumbia University scientists joined with more
than 1,000 other scientists from around the world in generating the hottest and most dense
matter ever observed. In addition
to providing a window into how
the universe was formed, the discovery promises to offer a greater
understanding of the qualities that
hold atomic matter together.
“The discovery of this state of
matter is relevant because it’s
probably the same sort of stuff
from which everything we see
around us originated,” said
William A. Zajc, a physics professor at the University, who has
been involved with the project
since 1986. “That is, it’s the very
dense matter that was present in
the first few microseconds after
the big bang.”
Using the Relativisitic Heavy
Ion Collider (RHIC) at the
Brookhaven National Laboratory
in Upton, New York, scientists
have been colliding sub-atomic
particles and recording the results
for several years as part of a
research project called Pioneering
High Energy Nuclear Interaction
Experiment (PHENIX).
Columbia professors have a
longstanding working relationship
with Brookhaven, and have been
involved in a leadership role with
RHIC and PHENIX since their
inception. Zajc has managed the
experiment as its spokesperson
since 1997.
Beginning in the summer of
2000, a series of experiments were
performed where the nuclei of
gold atoms were collided into
each other. The recorded results
were an anomaly when compared
with previously recorded collisions. In the past, a recorded collision between two nuclei, which
RECORD PHOTO BY EILEEN BARROSO
A birds-eye view of PHENIX at the Brookhaven National Laboratory in Upton, New York.
reaches temperatures of more than
a trillion degrees, would typically
exhibit two back-to-back jet signatures—the result of a pair of
quarks being knocked out of a
proton or neutron. Each jet represents the subatomic particles as
they pass through each other. In
this new collision, however, only
one jet was visible. A second
series of experiments illustrated
similar results.
Physicists theorized that the
collisions had melted the nuclei
down to their most basic components, or to what is referred to as
quark-gluon plasma. The second
jet was not visible because the
super dense material may have
absorbed it. This state of matter
has never before been observed
and is believed to be how the universe was composed a few millionths of a second after its birth.
To bolster their assertions, the
scientists ran a controlled collision
of gold nuclei and smaller, lighter
Microsoft Vice President Rick
Rashid Speaks at Computer Science
Distinguished Lecture Series
RECORD PHOTO BY EILEEN BARROSO
Rick Rashid, senior vice president of Microsoft research, explored
with computer science students the company’s research, technology
transfer, incubation process and new initiatives using Smart Personal Object Technology (SPOT). He gave the first in a series of 200304 Department of Computer Science’s Distinguished Lectures. For
more information, visit
http://www.cs.columbia.edu/lectureseries_rashid.html
deuterium nuclei. These deuterium-gold collisions produced only
two-jet signatures. A one-jet signature would have indicated that
the reaction observed between the
two heavy gold nuclei was not
unique, and hence not of significance. But all the collisions
between the heavy gold nuclei
and the lighter deuterium resulted
in two jets. This controlled measurement points to the creation of
quark-gluon plasma.
“The particular effect we were
studying is an unusual suppression of the high momentum particles that are expected to emerge
from such collisions if the matter
were transparent,” said Professor
Zajc. “The very fact that it is not
transparent, but instead results in
nearly complete suppression of
high momentum particles, indicates that we have formed the
densest matter ever created.”
Columbia’s faculty participation in PHENIX is much like a
two-sided coin, as theorists and
researchers work in tandem in
search of discovery. Zajc and
Brian Cole, a physics professor at
the University, are intricately
involved with the research itself.
Working with Columbia’s Senior
Engineer Bill Sippach and Associate Research Scientist Cheng-Yi
Chi, Cole oversaw much of the
electronics and real-time computing that were built specifically for
RHIC at Columbia’s Nevis Laboratories in Irvington.
Miklos Gyulassy, Norman
Christ, Alfred Mueller and Robert
Mawhinney are theoretical physicists. They had long theorized that
a simpler state of matter could be
created and was attainable; but it
has been the researchers’ job to
create the matter and measure its
existence through their work at
PHENIX.
Zajc was quick to point out that
the evidence is less than conclusive, and that much more testing is
required to confirm that they had
in fact created quark-gluon plasma. “I would call it [evidence]
persuasive, but not conclusive. It’s
crucial to note that persuasive
doesn’t cut it in the scientific literature, and attempting to sell persuasive as conclusive is not conducive to good science.”
Zajc will lead further testing at
PHENIX over the next several
years to confirm their creation and
to further explore the anatomy of
the atom.
Gyulassy—the
theorist—
believes the findings were more
than convincing and will open a
new realm of research. “The new
data confirmed our theoretical predictions. The data, together with a
new type of elliptic motion of the
thousands of produced particles
discovered previously, convince
me that quark gluon plasma has
been produced. Now the exploration of its properties can begin.”