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Posts Tagged ‘QGP’

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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What is the QGP?

Wednesday, November 23rd, 2011

Heavy ion collisions allow us to recreate the density and temperature that existed at the very beginning of the universe, before the universe was 10-6 s old, in a laboratory environment. Studying the resulting hot dense matter, which we call a quark gluon plasma (QGP), allows us to both better understand the evolution of the universe and one of the four fundamental forces of nature, the strong force. The strong force, which is more properly called Quantum Chromodynamics (QCD), is the force that binds protons and all other hadrons together.

The evolution of matter in the universe from the Big Bang to the present.

I will take a brief moment to remind everyone about some QCD basics before discussing the quark gluon plasma. QCD is one piece of the Standard Model, the theory that describes all subatomic particle interactions outside of gravity. QCD is carried by particles that physicists gave the tongue-in-cheek label of gluons. The only subatomic particles that can interact with gluons are quarks, of which there are 6: up, down, strange, charm, bottom and top. Each quark contains a QCD charge, which we call color. The anti-quarks have an anti-color charge, while gluons carry both color and anti-color charge. What does this mean? This means that gluons can interact with each other! This makes QCD calculations quite complicated.

There are two aspects to QCD that are important to understand with respect to the quark gluon plasma: quark confinement and asymptotic freedom. At the temperatures and densities that we observe outside of heavy ion collisions, QCD keeps quarks confined within their parent hadrons. This means we have never observed a bare quark! At extremely high energies, the QCD field strength lowers until the quarks no longer feel the force, which we call asymptotic freedom. In a very dense medium, such as what we create in heavy ion collisions it easier for quark-antiquark pairs to pop into existence than it is for these pairs to do so in a vacuum. These quark anti-quark pairs lower the QCD field strength, which lowers the energy needed for the quarks to be free.

So returning to the original question. What is a QGP? The QGP is a medium so dense and hot that the quarks and gluons within it are no longer confined to their original hadrons. But in order to discuss the properties of a medium, it needs to be in local thermalization. The concept of temperature only has meaning when thermalization has occurred because temperature is a bulk matter quantity. How hot is it? The QGP is hotter than 175 MeV, or 400,000,000 times the temperature of the surface of the sun!

What does it mean for the quarks to be deconfined? Originally, physicists tried to model the QGP as a weakly-coupled gas, but those models failed. The idea was that the deconfined quarks would behave similar to an ideal gas. Physicists have achieved reasonable success in modeling the QGP as an ideal fluid, in fact the most perfect liquid known to man . The fact that this model fits the data better means that even though the quarks are not confined within hadrons, they still interact with each other. This model of QGP is sometimes called sQGP, where the s stands for strongly coupled.

Next I will discuss some key QGP signatures and how we are looking for them at ALICE.

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“Hello” from Brookhaven National Laboratory, the land of quarks, nanoparticles, proteins, superconductors, and lots of deer and wild turkeys. We’re really excited to be a part of this new version of Quantum Diaries along with our friends from CERN, Fermilab, and TRIUMF. Through this blog, we’ll focus on one very important piece of Brookhaven’s multidisciplinary research portfolio: physics.

The independent discovery of the J/psi by Samuel Ting (front) of the Massachusetts Institute of Technology, at BNL's Alternating Gradient Synchrotron, and by Burton Richter, of the Stanford Linear Accelerator Center, earned its co-discoverers the 1976 Nobel Prize in physics. Shown with Ting in this photo are members of his experimental team.

From its early history, Brookhaven Lab has played a leading role in the exploration of matter and the early universe through groundbreaking nuclear and particle physics experiments. In fact, five of the Lab’s seven Nobel Prizes were awarded for physics research.

Today, Brookhaven continues this leadership role through several large-scale facilities on our site and around the world. At the Relativistic Heavy Ion Collider (RHIC), a 2.4-mile particle racetrack, scientists collide beams of “heavy ions” – the nuclei of atoms as heavy as gold – to replicate conditions microseconds after the Big Bang. This research has led to a series of stunning discoveries, including quark-gluon plasma, a “perfect”-liquid state of matter that permeated the early universe.  In addition to colliding heavy ions, RHIC is able to collide single protons to reveal details about a puzzling property called “spin.”

(more…)

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