We’re Getting Closer to Understanding How Our Universe Began by Solving a Cosmic Puzzle: “Perfect Fluid”

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Big Bang Concept

Berkeley Lab research brings us closer to understanding how our universe began.

Scientists have reported new clues to solving a cosmic conundrum: How the quark-gluon – nature’s perfect fluid – evolved into matter.

A few millionths of a second after the , the early universe took on a strange new state: a subatomic soup called the quark-gluon plasma.

And just 15 years ago, an international team including researchers from the Relativistic Nuclear Collisions (RNC) group at Lawrence Berkeley National Laboratory (Berkeley Lab) discovered that this quark-gluon plasma is a perfect fluid – in which quarks and gluons, the building blocks of protons and neutrons, are so strongly coupled that they flow almost friction-free.

Scientists postulated that highly energetic jets of particles fly through the quark-gluon plasma – a droplet the size of an ’s nucleus – at speeds faster than the velocity of sound, and that like a fast-flying jet, emit a supersonic boom called a Mach wave. To study the properties of these jet particles, in 2014 a team led by Berkeley Lab scientists pioneered an atomic X-ray imaging technique called jet tomography. Results from those seminal studies revealed that these jets scatter and lose energy as they propagate through the quark-gluon plasma.

But where did the jet particles’ journey begin within the quark-gluon plasma? A smaller Mach wave signal called the diffusion wake, scientists predicted, would tell you where to look. But while the energy loss was easy to observe, the Mach wave and accompanying diffusion wake remained elusive.

This 2010 video describes collisions of heavy particles at Brookhaven National Laboratory’s Relativistic Heavy Ion Collider. In 2005, RHIC physicists announced that matter created in the accelerator’s most energetic collisions behaves like a nearly perfect liquid. The properties of this fluid, the quark-gluon plasma, help us to understand the properties of matter in the early universe. Credit: Brookhaven National Laboratory

Now, in a study published recently in the journal Physical Review Letters, the Berkeley Lab scientists report new results from model simulations showing that another technique they invented called 2D jet tomography can help researchers locate the diffusion wake’s ghostly signal.

“Its signal is so tiny, it’s like looking for a needle in a haystack of 10,000 particles. For the first time, our simulations show one can use 2D jet tomography to pick up the tiny signals of the diffusion wake in the quark-gluon plasma,” said… Brinkwire News Summary.

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