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RHIC and the EIC

The Electron-Ion Collider (EIC) at Brookhaven Lab will reuse key infrastructure from the Relativistic Heavy Ion Collider (RHIC) and build on discoveries at RHIC and the Continuous Electron Beam Accelerator Facility (CEBAF) at Thomas Jefferson National Accelerator Facility (Jefferson Lab). But the EIC will have new features that greatly expand our ability to explore the building blocks of visible matter.

RHIC: Two ion accelerator/storage rings (inside RHIC tunnel).

EIC: One ion accelerator/storage ring plus one electron accelerator ring and one electron storage ring.

RHIC: Both rings carry ions (any atomic nuclei from protons—hydrogen nuclei—to uranium).

EIC: One existing ion ring will carry ions (protons or other atomic nuclei) just like RHIC; a new electron storage ring will carry electrons after they have been accelerated by the new electron accelerator ring.

conceptual image of a RHIC collision

RHIC: Collides two beams of ions; the two beams can be the same (for example, proton-proton, gold-gold), or one can have protons and the other heavier ions (proton-gold).

conceptual image of an EIC collision

EIC: Collides electrons with ions (protons or other atomic nuclei).

RHIC: Recreates matter as it existed just after the Big Bang nearly 14 billion years ago.

EIC: Probes the internal structure of nuclear matter as it exists today.

RHIC: Collisions of heavy ions “melt” atomic nuclei to “set free” the quarks and gluons that make up the protons and neutrons of the nuclei; the result is a hot soup of these fundamental particles, a quark-gluon plasma (QGP)—a substance that filled the entire universe just after the Big Bang, before quarks and gluons coalesced to form protons and neutrons of ordinary matter.

EIC: Electrons colliding with ions will exchange virtual photons with the nuclear particles to help scientists “see” inside the nuclear particles; the collisions will produce precision 3-D snapshots of the internal arrangement of quarks and gluons within ordinary nuclear matter; like a combination CT/MRI scanner for atoms.

RHIC: Allows scientists to study what happens as the “early universe” QGP cools down to form composite particles (protons and neutrons).

EIC: Electrons can “pick out” individual quarks from the protons that make up nuclei. Studying how those quarks recombine to form composite particles will inform our understanding of how today’s visible matter evolved from the QGP studied at RHIC.

conceptual illustration of the strong nuclear force

RHIC: Offers insight into the strong nuclear force, the strongest but least-understood force in nature, which holds the quarks together within protons, neutrons, and nuclei. 

EIC: Will offer new insight into the strong nuclear force, including how it keeps quarks and gluons confined in ordinary matter and builds up the mass and spin of the building blocks of nuclear matter.

conceptual image of gluon saturation

RHIC: Found indirect hints that gluons within nuclear matter multiply to reach a state of saturation, known as a color glass condensate (CGC), as they flit in and out of existence inside nuclear particles accelerated to near the speed of light. 

EIC: Will explore in detail and establish definitively whether a saturated state of gluons known as color glass condensate (CGC) exists at these energies. If the EIC finds the CGC, it will study the properties of this novel state of matter in detail by varying the energy and the nuclear ions colliding with the electrons.

RHIC polarization image

RHIC: Can collide two beams of polarized protons (where particles’ spin orientations are aligned in a particular direction) to study proton spin—a property somewhat analogous to the way a toy top rotates on its axis, which establishes the particle’s angular momentum.

EIC polarization image

EIC: Both proton and electron beams will be polarized for precision studies of proton spin.

spin puzzle diagram

RHIC: Has revealed that gluons and a sea of quark-antiquark pairs make essential contributions to proton spin.  

EIC: Will precisely measure how much gluons, quarks, and a sea of quark-antiquark pairs contribute to proton spin to solve the longstanding physics puzzle (or spin crisis) created when physicists discovered that a proton’s three main constituent quarks cannot account for its total spin. It will also make measurements that directly reveal the rotational motion of quarks and gluons.

Brookhaven National Lab's EIC Directorate coordinates with domestic and international partners to deliver the EIC construction project.

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Brookhaven National Laboratory advances fundamental research in nuclear and particle physics to gain a deeper understanding of matter, energy, space, and time; applies photon sciences and nanomaterials research to energy challenges of critical importance to the nation; and performs cross-disciplinary research on climate change, sustainable energy, and Earth’s ecosystems.