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August 03, 2010

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Physicists report creating hottest temperatures ever in lab

Feb. 16, 2010
Courtesy DOE/Brookhaven National Laboratory 
and World Science staff

Phys­i­cists re­port that they have cre­at­ed mat­ter at the hot­test tem­per­a­ture ev­er reached in a lab­o­r­a­to­ry, about 250,000 times hot­ter than the cen­ter of the Sun. 

The find­ings, aimed at un­veil­ing the fun­da­men­tal struc­ture of at­oms, come from the Rel­a­tiv­is­tic Heavy Ion Col­lider, an at­om smash­er at the U.S. De­part­ment of En­er­gy’s Brook­ha­ven Na­tional Lab­o­r­a­to­ry in New York.

To reach the tem­per­a­ture of about 4 tril­lion de­grees Cel­si­us, charged gold at­oms trav­el­ing at nearly light speed were bashed in­to each oth­er af­ter ac­cel­er­at­ing along the machine’s 2.4-mile (al­most 4 km) cir­cum­fer­ence.

The tem­per­a­ture is high­er than that needed to melt pro­tons and neu­tron­s—the kernel-like cores of at­oms—in­to a soup of their own con­stit­u­ent par­t­i­cles, quarks and glu­ons, phys­i­cists said. De­tails of the find­ings are to be pub­lished in the jour­nal Phys­i­cal Re­view Let­ters.

Sci­entists be­lieve such a soup, called a quark-gluon plas­ma, filled the uni­verse a few mil­lionths of a sec­ond af­ter it orig­i­nat­ed 13.7 bil­lion years ago. The plas­ma then cooled and con­densed to form the pro­tons and neu­trons that make up at­oms — and thus stars, plan­ets, and peo­ple. “This re­search of­fers sig­nif­i­cant in­sight in­to the fun­da­men­tal struc­ture of mat­ter and the early uni­verse,” said Wil­liam F. Brinkman, di­rec­tor of the De­part­ment of En­er­gy Of­fice of Sci­ence.

Sci­en­tists meas­ure the tem­per­a­ture of hot mat­ter by look­ing at the col­or, or en­er­gy dis­tri­bu­tion, of light emit­ted from it — si­m­i­lar to the way one can tell that an iron rod is hot by look­ing at its glow. 

The new find­ings sup­port a sur­pris­ing con­clu­sion that that quarks and glu­ons in the plas­ma be­have “much more co­op­er­a­tive­ly” than they were in­i­tially pre­dicted to do, said Ste­ven Vig­dor, Brook­ha­ven’s as­so­ci­ate lab­o­r­a­to­ry di­rec­tor for nu­clear and par­t­i­cle phys­ics, who over­sees the col­lider re­search.

Al­though the mat­ter pro­duced at the col­lider sur­vives for much less than a bil­lionth of a tril­lionth of a sec­ond, its prop­er­ties can be de­ter­mined us­ing the machine’s de­tec­tors to study the thou­sands of par­t­i­cles emit­ted dur­ing its brief life­time. The meas­urements are be­lieved to pro­vide new in­sights in­to Na­ture’s strongest force — in es­sence, what holds the pro­tons and neu­trons of the uni­verse to­geth­er.

Pre­dic­tions made before the col­lider’s first opera­t­ions in 2000 sugg­ested the quark-gluon plas­ma would be­have as a gas, re­search­ers said. But sur­pris­ing da­ta from the col­lider’s first three years of opera­t­ion, pre­sented by col­lider sci­en­tists in April 2005, in­di­cat­ed that the mat­ter pro­duced be­haves as a liq­uid, whose con­stit­u­ent par­t­i­cles in­ter­act very strongly among them­selves.

This liq­uid mat­ter has been de­scribed as nearly “per­fect” in the sense that it flows with al­most no fric­tion­al re­sist­ance. Such a “per­fect” liq­uid does­n’t fit with the pic­ture of “free” quarks and glu­ons phys­i­cists had pre­vi­ously used to de­scribe the plas­ma, phys­i­cists said.

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Physicists report that they have created matter at the hottest temperature ever reached in a laboratory, about 250,000 times hotter than the center of the Sun. The findings, aimed at unveiling the fundamental structure of atoms, come from the Relativistic Heavy Ion Collider, an atom smasher at the U.S. Department of Energy’s Brookhaven National Laboratory in New York. To reach the temperature of about 4 trillion degrees Celsius, charged gold atoms traveling at nearly light speed were bashed into each other after accelerating along machine’s the 2.4-mile (almost 4 km) circumference. The temperature is higher than that needed to melt protons and neutrons—the kernel-like cores of atoms—into a soup of their own constituent particles, quarks and gluons, physicists said. Details of the findings are to be published in the journal Physical Review Letters. Scientsits believe such a soup, called a quark-gluon plasma, filled the universe a few millionths of a second after it originated 13.7 billion years ago. “This research offers significant insight into the fundamental structure of matter and the early universe,” said William F. Brinkman, director of the Department of Energy Office of Science. Scientists measure the temperature of hot matter by looking at the color, or energy distribution, of light emitted from it — similar to the way one can tell that an iron rod is hot by looking at its glow. The new findings support a surprising conclusion that that quarks and gluons in the plasma behave “much more cooperatively” than they were initially predicted to do, said Steven Vigdor, Brookhaven’s associate laboratory director for nuclear and particle physics, who oversees the collider research. Scientists believe a similar plasma existed a few millionths of a second after the birth of the universe. The plasma then cooled and condensed to form the protons and neutrons that make up atoms — and thus stars, planets, and people. Although the matter produced at the collider survives for much less than a billionth of a trillionth of a second, its properties can be determined using the machine’s detectors to study at the thousands of particles emitted during its brief lifetime. The measurements are believed to provide new insights into Nature’s strongest force — in essence, what holds the protons and neutrons of the universe together. Predictions made prior to RHIC’s initial operations in 2000 expected that the quark-gluon plasma would behave as a gas. But surprising data from the collider’s first three years of operation, presented by collider scientists in April 2005, indicated that the matter produced behaves as a liquid, whose constituent particles interact very strongly among themselves. This liquid matter has been described as nearly “perfect” in the sense that it flows with almost no frictional resistance. Such a “perfect” liquid doesn’t fit with the picture of “free” quarks and gluons physicists had previously used to describe the plasma, physicists said.