From Brookhaven Lab: “The Glue that Binds Us All”

A QGP is formed at the collision point of two relativistically accelerated gold ions in the center of the STAR detector at the Relativistic Heavy Ion Collider [RHIC] at the Brookhaven National Laboratory.
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How an electron-ion collider could help unravel what makes matter stick together and what puts the spin on protons

“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.

This animation shows the strength of the gluon force field between a quark (at the center of the images) and an anti-quark, which grows as the energy of the nucleus increases. At low boost energies, the force fields are spread out (shown by larger “blobs”) and are comparable to the “strong” force that binds quarks together in the proton. At higher boost energies, force field fluctuations are incredibly strong — 10 times greater than the typical strong force — and localized at much shorter distances than the proton size. These “higher resolution” snapshots are cleaner to interpret than those at low boost energies and provide important clues to figuring out the nature of the glue binding together visible matter in the universe.

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.

‘An electron-ion collider would be the brightest, highest-intensity femtoscope to shine on the structure of matter,’ said Brookhaven theoretical physicist Raju Venugopalan, referring to its ability to discern structures at the scale of femtometers — that’s 10-15 meters, a millionth of a nanometer, or a millionth of a billionth of a meter!

‘Snapshots’ of matter at that scale over a wide range of energies would offer deeper insight into the substructure of the nucleus, its constituents, and particularly its smallest components, the quarks and gluons and how they interact.

‘Increasingly, it’s looking as if gluons and their interactions may hold the keys to many of our puzzles,’ Venugopalan said. An electron-ion collider would be the ideal tool for gazing at the ‘glue’ under conditions where scientists believe that it completely dominates the structure of neutrons, protons, and nuclei.

The particle tracks observed in RHIC’s detectors (extreme right) contain fingerprints or clues that reflect the conditions very early in heavy ion collisions, when gluons in the colliding ions were just starting to interact. This is somewhat analogous to the way the structure we see in the universe today is a reflection of structural aspects “frozen out” very early in the history of the universe (left). In each frame, time runs from left to right, but over a span of 13.7 billion years in the left frame and only billionths of a second in the right frame. Scientists can learn a lot about these early conditions by looking back, but they’d also like to probe the earliest stage of ion collisions directly. An electron-ion collider would make that possible.

Glue holds the key.”.

That last line, “Glue holds the key’, is the lead for the rest of this very interesting article. See the full article here.

One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

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