The soup of fundamental particles called the quark-gluon plasma can swirl far faster than any known fluid – faster than the mightiest tornado or the superstorm that is Jupiter’s Great Red Spot.
The results, published Aug. 3 in the journal Nature, come from a new analysis of data from the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory.
“Any liquid, like the coffee in a cup, can be stirred to produce a vortex,” said Manuel Calderon de la Barca, professor of physics at UC Davis and a member of the STAR collaboration which carried out the work. “The key to this paper is that we are able to measure how the quark-gluon plasma swirls, and we found that it does so far faster than any other fluid that has been studied in nature.”
Recreating the Early Universe
The quark-gluon plasma is an extremely hot mass of fundamental particles that filled the early universe and has been recreated by physicists with advanced accelerators such as Brookhaven’s RHIC. Far hotter than the center of the sun, the quark-gluon plasma has almost no viscosity, making it a “perfect fluid.” Any vortex that gets started in such a fluid should continue almost indefinitely.
By studying the properties of quark-gluon plasma, physicists hope to better understand the “strong force,” one of the fundamental forces in the Standard Model of particle physics, which binds quarks and gluons together to make protons and neutrons within atomic nuclei.
The researchers looked specifically for evidence of particles called lambda hyperons, whose decay they could measure with RHIC’s STAR detector and Time Projection Chamber.
A rotating object such as a vortex has angular momentum. This angular momentum gets imprinted on the particles that make up the vortex, and when these particles decay into others, that angular momentum is preserved, Calderon said.
By studying the spin of particles formed from decaying lambda hyperons, the researchers could therefore work back to the properties of the original vortices themselves.
Leading the analysis were Michael Lisa, a physicist at Ohio State University, and OSU graduate student Isaac Upsal. Professor Daniel Cebra, UC Davis Department of Physics, was also a co-author on the paper. A full list of the STAR collaborators is available here.
RHIC is a facility for nuclear physics research operated by the U.S. Department of Energy Office of Science. Research at RHIC and with the STAR detector is funded primarily by the Department of Energy and also by these agencies and organizations.
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Scientific paper: “Global Λ hyperon polarization in nuclear collisions: evidence for the most vortical fluid”