QCD Matter

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. Most recently, the Lab’s Relativistic Heavy Ion Collider (RHIC) — the world’s most powerful particle accelerator dedicated to nuclear physics research — has drawn collaborators from around the world to explore the most fundamental forces and properties of matter as it existed just after the Big Bang some 13 billion years ago. To date, this research has yielded a series of stunning discoveries, including:

  • The “perfect”-liquid nature of the quark-gluon plasma that permeated the early universe
  • “Bubbles” exhibiting local symmetry violations within the 4-trillion-degree quark-gluon soup
  • Exotic forms of antimatter that may help scientists refine models of neutron stars and explore fundamental asymmetries in the early universe

These discoveries have enriched physicists’ understanding of quantum chromodynamics (QCD), the theory that describes the so-called “strong” interactions of quarks and gluons — and illustrate ways in which the study of QCD matter can illuminate the evolution and current behavior of the universe.

RHIC RF cavity

Physicists examine the radiofrequency cavity system at the Relativistic Heavy Ion Collider.

Over the next decade, Brookhaven will continue its leadership role by enhancing and expanding RHIC’s ability to conduct precision studies of QCD matter to:

  • Quantify properties of the perfect liquid quark-gluon plasma, including details about its phase transition and role in the cosmos
  • Explore the role of gluons and gluon self-interactions in protons, neutrons, and nuclei
  • Probe what determines the key features of QCD and their relation to the nature of gravity, cosmology, and string theory
  • Map the universal properties of a dense gluon force field predicted to exist at the heart of all visible matter
  • Search for the missing source of proton spin among “soft” gluons

This research program will require the full utilization of RHIC with continuous accelerator and detector upgrades, including a phased path toward addition of an electron energy recovery linac to RHIC (creating eRHIC) for high-energy electron-nucleus collisions. Brookhaven is working with U.S. and international partners to build support for this program as a natural extension of the Lab’s existing core capabilities in nuclear physics, accelerator science, instrumentation, data distribution and analysis. The program will serve not just RHIC’s existing international user base of more than 1,000 scientists, but also a much broader research community exploring the connections of QCD matter to cosmology, astrophysics, and other fundamental interaction theories, including string theory —while also continuing to serve as a vital training ground for the next generation of scientists.

particle collisions recorded in the STAR detector

Computer rendering of a collision of two beams of gold ions in the STAR detector at Brookhaven's Relativistic Heavy Ion Collider