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Posts Tagged ‘quark-gluon plasma’

Heat: Adventures in the World's Fiery Places (Little Brown, 2013). If you haven't already fallen in love with the groundbreaking science that's taking place at RHIC, this book about all things hot is sure to ignite your passion.

Bill Streever, a biologist and best-selling author of Cold: Adventures in the World’s Frozen Places, has just published his second scientific survey, which takes place at the opposite end of the temperature spectrum. Heat: Adventures in the World’s Fiery Places features flames, firewalking, and notably, a journey into the heart of the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory.

I accompanied Streever for a full-day visit in July 2011 with physicist Barbara Jacak of Stony Brook University, then spokesperson of the PHENIX Collaboration at RHIC. The intrepid reporter (who’d already tagged along with woodland firefighters and walked across newly formed, still-hot volcanic lava—among other adventures described in the book) met with RHIC physicists at STAR and PHENIX, descended into the accelerator tunnel, and toured the refrigeration system that keeps RHIC’s magnets supercold. He also interviewed staff at the RHIC/ATLAS Computing Facility—who face the challenge of dissipating unwanted heat while accumulating and processing reams of RHIC data—as well as theorists and even climate scientists, all in a quest for understanding the ultrawarm.

The result is an enormously engaging, entertaining, and informative portrayal of heat in a wide range of settings, including the 7-trillion-degree “perfect” liquid quark-gluon plasma created at RHIC, and physicists’ pursuit of new knowledge about the fundamental forces and interactions of matter. But Streever’s book does more: It presents the compelling story of creating and measuring the world’s hottest temperature within the broader context of the Lab’s history, including its role as an induction center during both World Wars, and the breadth and depth of our current research—from atoms to energy and climate research, and even the Long Island Solar Farm.

“Brookhaven has become an IQ magnet, where smart people congregate to work on things that excite geniuses,” he writes.

Streever’s own passion for science comes across clearly throughout the book. But being at “the top of the thermometer” (the title of his final chapter, dedicated in part to describing RHIC) has its privileges. RHIC’s innermost beam pipes—at the hearts of its detectors, inside which head-on ion collisions create the highest temperature ever measured in a laboratory—have clearly left an impression:

“… I am forever enthralled by Brookhaven’s pipes. At the top of the thermometer, beyond any temperature that I could possibly imagine, those pipes explore conditions near the beginning of the universe … In my day-to-day life, bundled in a thick coat or standing before my woodstove or moving along a snow-covered trail, I find myself thinking of those pipes. And when I think of them, I remember that at the top of the thermometer lies matter with the audacity to behave as though it were absolutely cold, flowing like a perfect liquid…”

There’s more, a wonderful bit more that conveys the pure essence of science. But I don’t want to spoil it. Please read and share this book. The final word is awe.

The book is available for purchase through major online retailers and in stores.

-Karen McNulty Walsh, BNL Media & Communications Office

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The coolest and hottest fluid

Friday, October 19th, 2012

In September, the Large Hadron Collider (LHC) operators at CERN attempted a new trick: putting in collisions protons in one beam and lead ions in the other. Usually, the LHC operates with two beams of identical particles (protons or ions) circulating in opposite directions in the accelerator. Here is what is expected from this new setup.

These ions are atoms stripped of all their electrons, leaving only the nucleus. Lead ions contain 82 protons plus 126 neutrons, all held together by the nuclear force.  Protons are also composite objects made of three quarks and bound together by “gluons”, the particles carrying the nuclear force.

So when two such heavy ions collide at nearly the speed of light, I dare anyone to describe where each quark and each gluon will end up. Already, trying to predict where fifteen billiard balls go after breaking the pack is tough enough. But when each projectile is made of hundreds of particles, it becomes impossible.

At first glance, it would seem all we could get out of this is just a mess. But this turns out to be the coolest and hottest mess one will ever see. From the most energetic collisions comes a new form of matter called the quark-gluon plasma.

There are three very well known state of matter: solid, liquid and gaseous. Lesser known is the fourth state of matter called plasma. This is what one finds inside a neon tube when the electric current applied is strong enough to strip the gas of its electrons. Positively charged ions and negatively charged electrons float around freely, having enough energy not to recombine.

The quark-gluon plasma is just one step above this. Imagine there is enough energy around that not only the atoms but the nucleons (the name given to protons and neutrons, the particles found inside the nucleus) break apart and coexist in some sort of an extremely energetic fluid. This is as hot as it got instants after the Big Bang. What is so cool about it though, is that this plasma exhibits collective behavior, meaning quarks and gluons do not float freely but have collective properties. The most spectacular of them is that this fluid has no viscosity and behaves as a perfect fluid. If you try to confine it in a container, it just flows up the container’s wall and spread all over the place.

The ALICE experiment is dedicated to the study of the quark-gluon plasma. Each year, the LHC operates for a few weeks with lead ions instead of protons. ALICE collects data both during proton-proton collisions and heavy ions collisions. Even when only protons collide, the projectiles are not solid balls like on a billiard table but composite objects. By comparing what can is obtained from heavy ion collisions with proton collisions, the ALICE physicists must first disentangle what comes from having protons in a bound state inside the nucleus as opposed to “free protons”.

So far, it appears that the quark-gluon plasma only formed during heavy-ion collisions since they provide the necessary energy density over a substantial volume (namely, the size of a nucleus). Some of the effects observed, such as the number of particles coming out of the collisions at different angles or momenta, depend in part on the final state created. When the plasma is formed, it reabsorbs many of the particles created, such that fewer particles emerged from the collision.

By colliding protons and heavy ions, scientists hope to discern what comes from the initial state of the projectile (bound or free protons) and what is caused by the final state (like the suppression of particles emitted when a quark-gluon plasma forms).

Already, with only one day of data taken in this new mode, the ALICE collaboration just released two papers. The first one presents the measurements of the charged hadrons density produced in proton-ion collisions and compares the result with the same measurement after proper normalization performed in proton-proton and ion-ion collisions. The second compares the transverse momentum distributions of charged hadrons measured in proton-ions and proton-proton collisions.

The ultimate goal is to study the so-called “structure function”, which describes how quarks and gluons are distributed inside protons, when they are free or embedded inside the nucleus.

More will be studied during the two-month running period with protons colliding on heavy ions planned for the beginning of 2013.

A “snapshot” of the debris coming out of a proton-lead ion collision captured by the ALICE detector showing a large number of various particles created from the energy released by the collision.

Pauline Gagnon

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Torride et cool à la fois

Friday, October 19th, 2012

En septembre, les opérateurs du Grand Collisionneur de Hadrons (LHC) au CERN on réussi un truc nouveau : mettre en collision un faisceau de protons avec un faisceau d’ions de plomb. Habituellement, le LHC fonctionne avec deux faisceaux de particules identiques (protons ou ions) circulant en sens inverse dans l’accélérateur. Pourquoi cette nouvelle configuration ?

Ces ions sont des atomes auxquels on  a arraché tous les électrons, ne laissant que le noyau atomique. Les ions de plomb contiennent 82 protons plus 126 neutrons, le tout maintenu ensemble par la force nucléaire.  Les protons sont eux aussi des particules composites puisqu’ils sont faits de trois quarks « collés » ensemble grâce aux « gluons », les particules associées à la force nucléaire.

Alors quand de tels noyaux entrent en collision à presque la vitesse de la lumière, qui pourrait prédire où chaque quark et chaque gluon aboutira? Même avec seulement quinze balles de billard, il est pratiquement impossible de deviner où elles iront après la casse.  Si, de surcroit, chaque projectile est fait de centaines de particules, cela devient totalement imprévisible.

A première vue, il semblerait que tout ce qui peut sortir de collisions ions-ions est un fouillis incroyable. Mais en fait, ces collisions super énergétiques produisent le fouillis le plus torride et le plus cool qui soit : un plasma de quarks et gluons.

Tout le monde connaît les trois états de la matière: solide, liquide et gazeux mais le quatrième état, le plasma, est lui bien moins connu. C’est ce qu’on retrouve dans un tube au néon quand la différence de potentiel appliquée est assez forte pour arracher tous les électrons du gaz. Les ions chargés positivement ainsi que les électrons flottent librement, ayant suffisamment d’énergie pour ne pas se recombiner.

Le plasma de quarks et gluons est juste l’étape suivante. Imaginez qu’on fournisse suffisamment d’énergie pour pouvoir dissocier non seulement les atomes mais aussi les noyaux et mêmes les nucléons (le nom générique donné aux neutrons et protons à l’intérieur des noyaux atomiques). On obtient alors une soupe extrêmement énergétique de quarks et de gluons.

Il n’y a pas plus chaud et ce serait l’état dans lequel se trouvait toute la matière immédiatement après le Big Bang. Fait étonnant : le plasma de quarks et gluons se comporte comme un fluide ayant des propriétés collectives et non comme un ensemble de particules indépendantes. C’est en fait un fluide parfait ayant une viscosité nulle. Si on essayait de le confiner dans un contenant, le fluide remonterait les parois du contenant et se répandrait au maximum. Plus cool que ça et tu meurs…

L’expérience ALICE se consacre justement à l’étude de ce plasma. Chaque année, le LHC opère pour quelques semaines avec des ions de plomb au lieu des protons. ALICE accumule des données durant les collisions protons-protons et celles d’ions lourds. Même lorsque ce sont seulement des protons qui entrent en collision, les projectiles ne sont pas des balles pleines comme au billard mais bien des objets composites. En comparant ce que l’on obtient à partir de collisions d’ions ou de protons, les physicien-ne-s d’ALICE doivent d’abord distinguer ce qui vient du fait que les projectiles sont des protons liés dans le noyau ou bien à l’état libre.

Jusqu’à maintenant, il semble que le plasma de quarks et gluons ne se forme que dans les collisions d’ions puisqu’ils sont les seuls à fournir la densité d’énergie requise sur un volume assez substantiel (le volume d’un noyau atomique). Certains des effets observés, comme le nombre  de particules à émerger du plasma de quarks et gluons à différents angles ou vitesses dépend en partie de la nature de l’état final créé. Quand un plasma se forme, il réabsorbe une partie des particules émises, de telles sortent qu’on en voit beaucoup moins sortir de ces collisions.

Les collisions de protons sur des ions lourds permettront peut-être de démêler ce qui est attribuable à l’état initial (protons libres ou liés dans le noyau) et l’état final (comme lorsque le plasma réabsorbe une partie des particules émises).

Déjà, avec une seule journée d’opération à ce régime, la collaboration ALICE vient de publier deux articles scientifiques. Le premier article donne la mesure de la densité de hadrons chargés produits dans des collisions proton-ions comparée aux mêmes mesures effectuées avec des collisions protons-protons ou ions-ions, après avoir normalisé le tout. Le second article porte sur la comparaison des distributions de quantités de mouvement des hadrons chargés pour des collisions protons-protons et ions-ions.

Le but ultime est d’étudier les fonctions de structure des projectiles utilisés, c’est-à-dire décrire comment les quarks et les gluons sont distribués à l’intérieur des protons quand ils sont libres ou liés dans le noyau des ions de plomb.

Bien d’autres études suivront au début de 2013 durant la période de deux mois consacrée aux collisions protons-ions.

« Cliché » des débris d’une collision de proton-ion de plomb capturé par le détecteur ALICE montrant un grand nombres de particules diverses crées à partir de l’énergie dégagée.

 

Pauline Gagnon

 

Pour être averti-e lors de la parution de nouveaux blogs, suivez-moi sur Twitter: @GagnonPauline ou par e-mail en ajoutant votre nom à cette liste de distribution

 

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The Glue that Binds Us All

Wednesday, June 13th, 2012

RHIC, the Relativistic Heavy Ion Collider at Brookhaven Lab, found it first: a “perfect” liquid of strongly interacting quarks and gluons – a quark-gluon plasma (QGP) – produced by slamming heavy ions together at close to the speed of light. The fact that the QGP produced in these particle smashups was a liquid and not the expected gas, and that it flowed like a nearly frictionless fluid, took the physics world by surprise. These findings, now confirmed by heavy-ion experiments at the Large Hadron Collider (LHC) in Europe, have raised compelling new questions about the nature of matter and the strong force that holds the visible universe together.

Similarly, searches for the source of “missing” proton spin at RHIC have opened a deeper mystery: So far, it’s nowhere to be found.

To probe these and other puzzles, nuclear physicists would like to build a new machine: an electron-ion collider (EIC) designed to shine a very bright “light” on both protons and heavy ions to reveal their inner secrets. (more…)

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This story appeared in Fermilab Today July 29.
PHENIX, one of two major experiments located at the Relativistic Heavy Ion Collider (RHIC) based at Brookhaven National Laboratory, is upgrading again with help from Fermilab’s Slicon Detector Facility (SiDet). Fermilab technicians finished assembling hundreds of forward silicon vertex tracker (FVTX) detector components in early July.

One of the hundreds of forward silicon vertex tracker (FVTX) components assembled at Fermilab's Silicon Detector Facility. Photo: Vassili Papavassiliou, New Mexico State University

The wedge-shaped components will be installed in PHENIX to help scientists study the properties of quark gluon plasma (QGP), which theorists believe made up the universe moments after the Big Bang.

Eric Mannel, a physicist from Columbia University and one of about 450 PHENIX contributors, worked as an electronics project engineer overseeing the final stages of assembly at Fermilab.

“We want to understand how the universe evolved the way it did from the very beginning,” Mannel said. “The FVTX detector will provide a higher resolution for tracking of particles which will allow us to study the properties of QGP.”

QGP is a near-perfect liquid composed of disassociated quarks and gluons suspended in plasma. It is said to be nearly perfect because it contains almost no internal friction—if you were to stir the plasma, it would continue to swirl forever. Physicists create QGP by smashing heavy ions and protons together. SiDet personnel provided a technical capabilities unique to Fermilab, to construct detectors that will allow physicists to study those collisions in more detail than ever before.

“We anticipate that we’ll be able to reconstruct secondary vertices from the decay of charm and beauty quarks with a resolution of 70 microns. The typical decay lengths for those particles are several hundred microns in heavy-ion collisions at RHIC,” Mannel said. The average human hair is about 100 microns thick.

The SiDet team completed the microassembly of FVTX components in mid-July. From left to right: Tammy Hawke, Michelle Jonas, Nina Ronzhina, Bert Gonzalez and Mike Herron. Also part of the group is Hogan Nguyen, not pictured. The FVTX group of PHENIX collaborators are also not pictured: Eric Mannel, Vassili Papavassiliou, Elaine Tennant, AAron Veicht and Dave Winter. Photo: Reidar Hahn.

AAron Veicht, a Ph.D. student at Columbia University, spent nearly 10 months working with the technicians at SiDet and will be part of the team installing the detector in PHENIX this fall.

“I’ll get to see the project from the very early stages all the way through to analyzing the data, so it’s very exciting,” Veicht said. “I gained a lot of experience while working with the technicians at Fermilab. It was a vital part of my education.”

Bert Gonzalez was the Fermilab technical supervisor on the design project. “The process went quite well, as this was the first endeavor where we worked with program collaborators,” Gonzalez said. Gonzalez and his Fermilab team spoke with PHENIX collaborators via conference calls for most of the design and development of the components.

“It was a good run,” Gonzalez said. “The project will be missed at SiDet, because it was a concrete job; you could dig your hands into it.”

Veicht felt that the people at SiDet were helpful and knowledgeable.

“It was my first time at Fermilab, and it was absolutely fantastic,” Veicht said.

PHENIX detector. Photo: Brookhaven National Laboratory

PHENIX collaborators plan to commission the detector in October and begin data collection this January.

– Ashley WennersHerron

Related information:

*PHENIX website

*RHIClets: A collection of Java applet games about the RHIC collider and RHIC physics.

*PHENIX cartoons

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Quark Matter game cards

Want to “play” with subatomic particles? You could work at Brookhaven Lab’s Relativistic Heavy Ion Collider (RHIC) or the LHC — or you could play a new card game invented by a group of Hungarian students and RHIC/PHENIX collaborator Tamás Csörgő.

The students — Csaba Török and his friend Judit Csörgő (Tamás’ daughter) — invented the game as an entertaining way to learn about subatomic particles and their interactions, inspired by physics presentations in the science club at their secondary school, where Tamás was a frequent presenter.

The game, now available for purchase in both Hungarian and English, “provides a great opportunity for all people — not just physicists — to get acquainted with some of the elementary particles and concepts of the Standard Model,” said Csaba.

The deck consists of cards that represent particles and anti-particles from neutrinos, to electrons, positrons, muons, and quarks, which can be used for four different games. In “Quark Matter,” a game that models RHIC physics, the cards are mixed face up on a table, packed closely together to represent matter at the instant of collision — a quark-gluon plasma (QGP). The object for each player is to quickly extract particles as they would emerge from the collision, in order: non-interacting neutrinos and antineutrinos first, followed by electron/positron and muon/anti-muon pairs, and then quarks and anti-quarks as they hadronize, or freeze out, to form mesons, baryons, and anti-baryons — all while maintaining a neutral color charge.

Brookhaven's Educational Programs staff introduced the card game to students at Rocky Point Middle School.

As players race to extract cards, the “system” expands just as it does in a real RHIC collision. Players score points for each correct particle pick. More sophisticated players can name the particles as they extract them. Additional games teach and reinforce deeper concepts, such as weak decays and several laws of conservation.

For more information, visit particles card game.

-Karen McNulty Walsh, BNL Media & Communications

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