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Has matter's mother paid a call? (Hot Mama).



Physicists have found new signs that fiery particle collisions within a giant accelerator two years ago created a state of matter identical to what might have been the stuff of the newborn universe.

Stunning results announced this week are prompting a growing chorus of physicists to say that it's time to declare success in a decades-long quest to make quark-gluon plasma--an extremely hot, dense soup of matter that contains loose fundamental particles known as quarks and gluons Gluons

The hypothetical force particles believed to bind quarks into “elementary” particles. Although theoretical models in which the strong interactions of quarks are mediated by gluons have been successful in predicting, interpreting, and
 (SN: 8/26/00, p. 136).

"This really is a decisive moment," says theorist Miklos Gyulassy of Columbia University. "I feel, at this stage, we've actually seen it"

While mainly theorists take this stand, experimental physicists largely remain cautious.

Theorists have predicted that smashing together heavy atomic nuclei accelerated to nearly the speed of light can create a quark-gluon plasma. The resulting fireballs, which can reach temperatures measured in trillions of degrees, are expected to melt the protons and neutrons that compose ordinary nuclear matter. That process would briefly liberate the quarks and gluons that make up protons and neutrons.

Producing a quark-gluon plasma would replay in miniature the critical scene early in the cosmos when the plasma gave birth to ordinary matter, researchers say. Studying the plasma, scientists could expose the fundamental nature of matter and the vacuum that permeates the cosmos.

In experiments conducted earlier this year, physicists at Brookhaven National Laboratory Brookhaven National Laboratory, scientific research center, at Upton (town of Brookhaven), Long Island, N.Y. It was founded in 1947 by Associated Universities, a management corporation sponsored by nine eastern U.S. universities.  (BNL BNL Brookhaven National Laboratory (Upton, NY)
BNL Bibliothèque Nationale de Luxembourg (French)
BNL Banca Nazionale del Lavoro
BNL Berkeley National Laboratory
BNL Bare Naked Ladies
) in Upton, N.Y., smashed heavy gold nuclei with much lighter nuclei called deuterons--the nuclei of deuterium deuterium (dtēr`ēəm), isotope of hydrogen with mass no. 2. The deuterium nucleus, called a deuteron, contains one proton and one neutron. , a hydrogen isotope. The researchers produced those collisions in the lab's Relativistic Heavy Ion Collider The Relativistic Heavy Ion Collider (RHIC, pronounced like "rick", IPA: /ˈrɪk/) is a heavy-ion collider located at and operated by Brookhaven National Laboratory (BNL) in Upton, New York. , or RHIC--a giant device that is now the main tool in the hunt for the quark-gluon plasma.

Creating a quark-gluon plasma wasn't the aim of these experiments. The goal was to determine whether observations from earlier RHIC RHIC Relativistic Heavy Ion Collider (Brookhaven National Lab)
RHIC Radio Hypnotic Intracerebral Control
RHIC Radiation Hardened Integrated Circuit
 experiments could be explained with theories that don't summon the quark-gluon plasma.

The new gold-deuteron tests focused on jets of particles emanating from the collisions. Jets are produced when two highly energetic quarks bounce off each other. If one or both escape the fireball fireball, very bright meteor leaving a trail in the sky that can remain visible for several minutes; often a distinct sound, perhaps caused by very low frequency radio waves, is associated with it. , they break up into sprays of other particles. Such jets may show up as single bursts or oppositely directed pairs.

However, during the previous RHIC experiments, scientists had observed that collisions between pairs of gold nuclei yielded fewer jets than would be expected at that collision energy.

Physicists had come up with two explanations for the discrepancy. In one scenario, if energetic quarks collide at a fireball's edge, the quark heading away from the collision's center might get away while its partner bogs down in the soup of still agitated ag·i·tate  
v. ag·i·tat·ed, ag·i·tat·ing, ag·i·tates

v.tr.
1. To cause to move with violence or sudden force.

2.
, colliding particles--the quark-gluon plasma.

Alternatively, some physicists suggested, a subtle property of nuclei known as gluon gluon, an elementary particle that mediates, or carries, the strong, or nuclear, force. In quantum chromodynamics (QCD), the quantum field theory of strong interactions, the interaction of quarks (to form protons, neutrons, and other elementary particles) is  saturation could have caused the jet suppression.

To sort out what was happening, the RHIC teams turned to the less energetic collisions between gold ions and deuterons. If gluon saturation were at work, jet suppression would persist at these lower energies. If not, jets would emerge in undiminished numbers because the gold-deuteron impacts generate too little energy to create a jet-absorbing quark-gluon plasma.

Jets weren't suppressed, three independent RHIC teams announced Wednesday at a BNL colloquium col·lo·qui·um  
n. pl. col·lo·qui·ums or col·lo·qui·a
1. An informal meeting for the exchange of views.

2. An academic seminar on a broad field of study, usually led by a different lecturer at each meeting.
. The stunning implication is that a quark-gluon plasma had been present in the gold-gold experiments.

Nonetheless, most of the hundreds of physicists who have been conducting the RHIC experiments don't consider the case closed, say members of those teams. Despite the new findings and other, previous hints of quark-gluon plasma at RHIC, a stronger case will require observing several additional features of collision debris to rule out some other form of hot, dense matter.

The experimentalists' reticence stems in part from fallout from an announcement 3 years ago by the European Laboratory for Particle Physics, or CERN CERN or European Organization for Nuclear Research, nuclear and particle physics research center straddling the French-Swiss border W of Geneva, Switzerland. , near Geneva Geneva, canton and city, Switzerland
Geneva (jənē`və), Fr. Genève, canton (1990 pop. 373,019), 109 sq mi (282 sq km), SW Switzerland, surrounding the southwest tip of the Lake of Geneva.
. Researchers stated that something akin to the quark-gluon plasma, if not the plasma itself, had been produced in an accelerator there (SN: 2/19/00, p. 117). To many other scientists, the announcement gave the impression that CERN researchers were prematurely claiming discovery of the quark-gluon plasma when rigorous proof of such a claim was still lacking.
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Title Annotation:creation of quark-gluon plasma
Author:Weiss, P.
Publication:Science News
Geographic Code:1USA
Date:Jun 21, 2003
Words:683
Previous Article:Down to it. (Letters).
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