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Planning for RHIC II and eRHIC

Today, the ultra-high temperatures of the early universe are approachable on Earth — but only inside the largest, highest energy particle accelerators. That is why the Relativistic Heavy Ion Collider (RHIC) was constructed at Brookhaven National Laboratory: to attempt to recreate quark-gluon plasma, a state of matter that is thought to have existed immediately after the Big Bang.

Once the existence of quark-gluon plasma is proven, however, two challenges will remain. The first is to characterize this primordial state of matter and its relationship to the fundamental features of today’s universe. The second is to look for color glass condensate. It is hypothesized to be the saturated, or maximum density, state that can be achieved at high energies by particles subject to the strong force, which is the short-range attraction binding atomic nuclei.

To undertake these tasks, Brookhaven has proposed and the U.S. Department of Energy is planning for two upgrades to RHIC: RHIC II and eRHIC.


The RHIC II upgrade will provide a ten-fold increase in the luminosity, or collision rate, enabling scientists to study particle collision events that happen only rarely and to explore states of matter believed to have existed during the first moments after the Big Bang.  - Facilities for the Future of Science: A 20-Year Outlook Office of Science, U.S. Department of Energy

Although RHIC’s gold-ion beams are energetic and intense enough for the plasma’s discovery and initial exploration, beams of even higher intensity are needed for a detailed examination of rare processes.

By upgrading RHIC into RHIC II, the collider’s luminosity, or collision rate, will be increased by a factor of ten, thereby increasing the rate of plasma production and the ability to study rare processes associated with the substance.

After examining the science intersecting physics and astronomy, the National Research Council of the National Academy of Sciences identified the existence of quark-gluon plasma as one of the most pressing research questions to be addressed in this field. In addition, the science underlying RHIC II received the highest ranking from a future-facilities subcommittee of the Nuclear Science Advisory Committee (NSAC), which reports to DOE’s Office of Science and to the National Science Foundation.


The addition of an electron accelerator to the current RHIC facility would create the world’s first electron-heavy ion collider, enabling the creation of an enormous number of gluons and presenting a unique opportunity to probe the substructure of particles.
- Facilities for the Future of Science

Since color glass condensate is another form of matter thought to exist in heavy nuclei accelerated to high energy, Brookhaven has proposed to turn RHIC into eRHIC, the world’s only electron-heavy ion collider.

Point-like and weakly interacting, the electron is an ideal probe of nuclear structure. Evidence from lower energy electron accelerators has, in fact, resulted in the prediction of color glass condensate. Some think that, before nuclei colliding at high energy can make quark-gluon plasma, they become densely compressed — a color glass condensate — in the direction they are being accelerated. Upon impact, color glass condensate is thought to “shatter,” thus forming the plasma.

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