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Mission Overview

The Electron-Ion Collider will be a discovery machine for unlocking the secrets of the "glue" that binds the building blocks of visible matter in the universe.

Building Upon Discovery

Some experiments in nuclear physics let physicists “go back in time” to study matter as it existed in the very early universe. These experiments have revealed intriguing details of the “perfect liquid”—a primordial soup made of quarks and gluons, the particles that form the protons and neutrons in visible matter. These experiments have also given scientists a vague glimpse of the inner structure of protons as they exist today, including how their constituents contribute to their properties, as well as hints of other intriguing states of matter and new questions to explore.

For example, while we know protons are made of quarks and gluons, we know little about how these building blocks are arranged. And while protons, along with neutrons, make up the bulk of everything we see in the universe, their constituent quarks account for only a small fraction of their mass.

That means gluons—massless particles that generate the glue-like force field of the strong nuclear force that holds quarks together—could account for more than 90 percent of the mass of visible matter in the universe. The question is: how?

While existing nuclear physics facilities continue to provide important insight and fresh data—pushing the limits of discovery well beyond their initial designs—there is only so far they can go toward unlocking the inner workings of the building blocks of matter. The Electron-Ion Collider will be a novel tool for exploring this inner microcosm dominated by gluons.

The U.S. Nuclear Science Advisory Committee recommends the expeditious completion of the EIC as the highest priority for facility construction in its 2023 Long Range Plan.

3D structure of protons and nuclei

The EIC will bring high-energy electrons into head-on collisions with high-energy protons or atomic nuclei to produce “freeze-frame” snapshots of those particles’ inner structure, creating the first-ever tomographic 3D images of the “ocean” of gluons within. These images will tell scientists how gluons and quarks bind each other to form the particles within and around us.


Gluon saturation and the color glass condensate

Recent experiments and advances in theory suggest that protons, neutrons, and nuclei appear as dense “walls” of gluons at high energies, creating what may be among the strongest force fields in nature. Discovering and studying this form of matter, the “color glass condensate,” will provide deeper insight into why matter in this subatomic realm is stable.


Solving the mystery of proton spin

The EIC will be the world’s first polarized electron-proton collider—meaning the “spins” of both colliding particles can be aligned in a controlled way. This will make it possible to experimentally solve the outstanding mystery of how the teeming quarks and gluons inside the proton combine their spins to generate the overall spin carried by the proton.


rendering of proton spin puzzle
rendering of proton spin puzzle

Quark and gluon confinement

Experiments at the EIC will offer novel insight into why quarks or gluons can never be observed in isolation, but must transform into and remain confined within protons and nuclei. The EIC—with its unique combinations of high beam energies and intensities—will cast fresh light into quark and gluon confinement, a key puzzle in the Standard Model of physics.


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.