A large-scale nuclear physics project at Carnegie Mellon that will lead to a better understanding of how subatomic particles called quarks are bound together has received the green light from the Department of Energy (DOE) as part of a major upgrade to the Thomas Jefferson National Accelerator Facility in Newport News,Va.

Called "GlueX," the experiment will spearhead new physics at the facility's Jefferson Lab, allowing scientists to address one of the greatest mysteries of modern physics — the mechanism that "confines" quarks inside protons and neutrons. In recent years, supercomputer models have indicated that fields called "flux-tubes" may be responsible for confining the quarks. By exciting these "flux-tubes" with high-energy beams of photons, the GlueX researchers hope to generate new families of particles that will lead to new information about quark interactions.

The DOE assigned GlueX and the accelerator upgrade "critical decision zero" status (or CD0), meaning that the underlying science is compelling and important. While much work remains before GlueX can begin, the announcement is a major step forward.

"We are particularly pleased to be leaders of this important project within the DOE Facilities Plan to explore the frontiers of science in the 21st century," said Fred Gilman, chair of the Physics Department.

The upgrade and GlueX form one of 28 scientific programs in the DOE's Plan, announced in November 2003. The upgrade, which includes the GlueX project, was one of 12 projects earmarked for construction in the first 10 years of the plan, and was one of the first to receive CD0 status.

"The CD0 announcement is an enormous political milestone that makes it possible for the GlueX team to bring in new international collaborators to work at Jefferson Lab. The GlueX collaboration is currently in discussions with groups from Canada, Greece and Mexico, and we expect interest from other groups," said Physics Professor Curtis Meyer.

Initially conceived in 1997, GlueX is the key experiment of a $200 million upgrade to the Jefferson Lab particle accelerator and facilities. Over 100 researchers from more than 20 institutions around the world, including Canada, Scotland, Russia and the United States, are committed to the renovation and experiment. The upgrade to the Jefferson Lab will double the accelerator beam energy to provide the high-energy photons needed. The renovation also includes a new experimental hall for GlueX.

The next step, according to Meyer, is a 12- to 15-month detailed study of project operations and costs. Researchers will also work on building and testing prototypes for the particle detectors for GlueX.

One prototype, a 200-piece central tracking device, is being constructed by Carnegie Mellon's internationally recognized Medium Energy Group, of which Meyer is a member (see [link to MEG story]).

However, not all of the detectors and equipment for GlueX are new. To save more than $15 million, the project is recycling a large magnet originally used at the Stanford Linear Accelerator and refitting a detector from the Brookhaven National Labs in New York used to detect high-energy particles.

Once the study is completed and approved, the DOE will release funds for the final design of GlueX. The next big step will establish internal performance guidelines for the project. This wll set the stage for the start of construction. The research team anticipates starting the experiment in early 2009.

Michael Katz-Hyman