[no subject]

[Brant Johnson <brant@bnl.gov>]

Dear PHENIXians and Friends,

	Marty Van Lith has forwarded me this news item related
to RHIC.  Thanks Marty.

Brant

Date: Fri, 31 Aug 2001 12:20:32 -0400
From: "VanLith, Martin" <vanlith@bnl.gov>
To: "Johnson, Brant" <brant@bnl.gov>
Subject: RHIC newsclip

Folks-
Here is a nice article on RHIC from the latest issue of Dan's Papers.
Scroll to the bottom of this page and click on the link if you would
like to see the article plus photo as they appear on their website.

The Search For Quarks
Brookhaven's RHIC Searches For Quarks And The Spin Within The Proton

By Jerry Cimisi

"In the seventies and eighties we started to learn about quarks. The
evidence became more and more convincing that they existed. But they
were so tightly bound in protons and neutrons that you could never get
them out. Whenever a new sublevel of particles was discovered, you could
always break them out, but with quarks it was not the case."

Thomas Ludlam, a senior physicist at Brookhaven National Laboratory, was
talking about the period that led to the design, construction and
deployment of RHIC, the Relativistic Heavy Ion Collider, which has
achieved the highest energy density in nuclear collisions of any atom
smasher in the world.

In a ringed complex with a circumference of 2.4 miles, ions (atoms
stripped of their electtrons) from gold atoms are sent smashing into one
another at just a fraction under the speed of light, 186,000 miles a
second, creating subatomic collisions at a temperature of a trillion
degrees Kelvin. Various detectors, such as STAR, PHENIX, BRAHMS and
PHOBOS, are situated along the circumference of the ring, gathering data
from the collisions.

"It was thought," said Ludlam, "that if matter could be heated to a
trillion degrees Kelvin it would melt and release the quarks. You would
have a new phase of matter, with just quarks. We believe that in the
very early universe matter was in this state."

The RHIC project is nothing less than an attempt to recreate the state
of matter moments after the Big Bang, and unleash a sea of quarks.

Just what, pray tell, is a quark?

First the name: Unwittingly, James Joyce had a hand in the appellation.
In his stream of consciousness novel, Finnegan's Wake, published in
1939, Joyce wrote a number of rhyming couplets (ending with a 13th
unrhymed line) that unfavorably depicted the cuckolded King Mark of the
Tristan legend:
"Three quarks for Muster Mark!
Sure he hasn't got much of a barkS"

In 1963, pioneering physicist Murray Gell-Mann, was trying to give a
name to what was thought to be the fundamental constituents of the
nucleus In his book, The Quark and the Jaguar, published decades later
in 1995, Gell-Mann wrote that he had the sound of the name, but not the
spelling. The sound was something like "kwork" (with the "o" sound as in
"coat"). Gell-Mann was in the habit of perusing Finnegan's Wake, and he
came across "Three quarks for Muster Mark," which he took to mean
Joyce's way (in the manner of Lewis Carroll's literary play) of saying,
"Three quarts for Mister Mark."

Quark was indeed a word, meaning the cry of a gull or a cawing. The
pronunciation of Gell-Mann's original name for the particle was close
enough to quark. Gell-Mann latched on to Joyce's word play, and thus
"quark" entered the lexicon of physics.

"In any case," he wrote, "the number three fitted perfectly the way
quarks occur in nature."

* * *

But what is a quark?

Quarks are believed to be the most fundamental of subatomic particles.
In other words, as far as we know, quarks cannot be broken down. Quarks
themselves are the constituents of protons and neutrons. There are six
"flavors" of quarks: up, down, strange, charm, top and bottom. The term
flavors came about because when quarks were first discovered there were
three of them, and they were called "vanilla, and chocolate." At any
rate, each flavor of quark is believed to come in three varieties,
differing in a property termed color.

A proton consists of two up quarks and a down quark, while a neutron has
two down quarks and an up quark.

The terms "up," "down," etc. have no physical meaning in the way we know
these words, they mere designate different types of quarks. The up and
down quarks have an energy range of 5-10 mega electron volts (MeV),
while the charm quark is about 1.5 giga electron volts (GeV) and the
strange quark is still larger, 150 MeV. Such large quarks do not
normally occur in nature, and such quarks would only be found in very
high energy collisions.

Regarding the years leading up to RHIC, Thomas Ludlam related that a
super-collider project called Isabelle had begun construction at
Brookhaven lab in the late '70s. Its purpose was to accelerate beams of
protons. But long before its completion, it was determined that it would
be feasible to build a much larger machine for such experiments, and the
Isabelle project was cancelled by the Department of Energy. That machine
quickly became dubbed the SSC, or Super-Conducting Super-Collider. The
larger, planned-for machine would not necessarily be at Brookhaven
National Laboratory. In the 1980s there was great debate in the
scientific community about just
where such a collider would be located. For a time it seemed as if a
location in Texas would be chosen.

Ludlam, a scientist at BNL in the mid '80s, headed a task force that
looked into the
feasibility of constructing a high energy collision project at the lab,
which began the
"long haul" to what is now the RHIC. He said, "The project was
technically different from Isabelle, but would use the tunnel that was
already in place."

Ultimately, in the late '80s, the Department of Energy and the National
Science Foundation approved what would become known as RHIC: the
Relativistic Heavy Ion Collider. Construction began in January, 1991.
Ludlam was associate director for overseeing the design and the
construction of the various detectors that would be placed about the
huge circumference of rings in the tunnel and was completed in 1999. The
first collisions took place in the summer of 2000.

The mission of RHIC was to recreate the state of matter moments after
the inception
of the universe. How successful has it been? Tim Hallman, spokesman for
the STAR (Solenoidal Tracking at RHIC) project, one of the particle
detectors, at RHIC, said, "The jury is still out on that."

He added that this year RHIC is operating at its full energy capacity,
as opposed to about 70 percent capacity last year, creating 40 terra
electron (TeV) volts per collision.

The total nucleons (protons plus neutrons) in the gold nucleus is 197.
When two gold ions collide, each pair of colliding nucleons produces 100
giga electron volts (GeV). Giga equals a million; terra equals a million
times a million. With 197 nucleons multiplied by 100 GeV, the total
energy per gold ion collision equals 40 TeV.

The numbers are large, and in the immediate vicinity of the collisions
the temperatures are astronomical (in fact, hotter than the sun) as
previously noted, but as Hallman remarked, "The energy released is in an
exceedingly small volume and lasting for an extremely brief time."

According to the Brookhaven National Laboratory's website, if a
quark-gluon plasma is formed in the RHIC collisions, it will last no
more than .000000000000000000000000001 seconds. In addition, for all the
high energy released on a subatomic scale, the impact of the particles
will be about the same as two mosquitoes colliding.

Speaking of the subatomic scale: in twenty years, RHIC will use about
one gram of
gold to produce the gold ions.

Hallman noted that "We have some idea from previous results how many
particles we should be producing at high speed collisions; so far we
have not been producing as many particles as we might expect. It is
possible that there is a new effect we don't know about, or an old
effect that is surprising us in a new way."

Hallman spoke about RHIC's other mission: the sum of the spin or angular
momentum) of the proton. The spin of particles is measured in units of
Planck's Constant, which is a constant of proportionality in regards to
the energy and frequency of a quantum unit of electromagnetic energy,
such as light or heat radiation.

"We think we understand all the components of protons," he said. "The
sum of the spin of the particles inside the proton should add up to the
spin of the proton. But, in fact, the sum is not as large as that of the
proton. The suspicion is that the extra sum comes from the gluons."
(Gluons are particles that are believed to hold the quarks together.)
"That is telling us that there is something happening there we don't
know about."

He added, "Pauli's Exclusion Principle states that two of the same types
of particles cannot occupy the same quantum state. The practical
consequences is that it keeps nuclei from collapsing; you can only pack
ferimons (electrons, protons and neutrons) so tightly."

If the question of the proton is explained, what practical applications
will come from
it?

Hallman said, 'There is no immediate practical application. But history
has taught us
that when you understand how matter works, something eventually comes
out of it."

* * *

Mark Baker of the PHOBOS Project at RHIC said, "We almost have as much
data as we had all of last year." He added, "It does take time to go
through it, but we do it quickly."

That data PHOBOS gathers counts how many particles come out of the
collisions at right angles. These would be the particles with the
highest degree of energy. Baker said, "When collisions happen, it is
like two pancakes hitting each other. The particles that come out at
right angles are more in the center of the collision."

He went on, "We are getting the number of particles in the realm of
prediction, but in the low end. Some models assumed a larger number of
collisions."

The silicon detectors of PHOBOS measure the temperature, size and the
density of the atomic collisions. The hope is this detector will observe
the phase transition between ordinary matter and the quark-gluon plasma
that is thought to have existed immediately after the beginning of the
universe.

Baker, who at twelve years old decided on physics as a career after
reading the science essays of Isaac Asimov, was part of the early
planning stages of RHIC. PHOBOS had begun as a larger project called
Mars before RHIC went into operation. When Mars was scaled back, the
project was renamed after one of the planet's moons.

There are eight groups in the PHOBOS project at RHIC. Baker is the
coordinator for these groups, and is the leader of the Brookhaven
National Laboratory group. Apart from the BNL group, the other seven are
from: Argonne National Laboratory in Chicago; the Institute for Nuclear
Physics, Cracow MIT; National Central University in Taiwan; University
of Rochester; University of Illinois at Chicago; and the University of
Maryland. At any given time there are fifty to a
hundred people working with PHOBOS.

In October, 2000, the PHOBOS group was the first to publish a paper - in
Physical Review Letters - on the first collisions at RHIC; and they are
first to submit a paper, also to Physical Review Letters - on data
gathered from collisions in 2001, at the full energy level of RHIC. This
paper is currently under review; it is expected it will be published
this autumn.

Baker talked about other aspects of RHIC. "It's amazing how much
non-physics we do each day." In overseeing the "nuts and bolts" of the
project, there were hiring considerations, visas for foreign scientists
and, of course, the budget.

That led him to speak about the energy considerations of RHIC.
"Refrigeration is the dominant cost." The magnets that line the long
rings of RHIC have to be kept at super-cool temperatures, minus 451.6
degrees, only a few degrees above absolute zero (-459F) the temperature
at which all movement ceases. The severe cold makes the magnets, which
are bathed in liquid helium, superconducting.

RHIC uses so much energy, Baker said, that a few times this summer, LIPA
had asked the lab to phase down operations in order to avoid a brownout
on Long Island.

In 2000 RHIC went online for only a few months. This year, under the
present operating budget, it will be initiating subatomic collisions
into January, 2002. If further monies are allocated, it will run into
the spring.

http://www.danspapers.com/paper/cimisi.html

----------
Jane Koropsak
Community Involvement, Government & Public Affairs
Brookhaven National Laboratory
email:  jane@bnl.gov