SeaQuest dives into a mysterious sea of particles

Scientists hope the SeaQuest detector will begin taking data in a couple of weeks. Photo: Reidar Hahn

Physicists at Fermilab will soon commission a new experiment that will slam protons into various targets to reveal the mysterious subnuclear interactions in the sea of particles within the proton. The SeaQuest experiment, conceived by a team of nuclear and particle physicists, aims to provide a new understanding of nucleon-nucleon interaction. With results from this experiment, they could possibly replace the current model of nuclear force with a new fundamental theory.

Physicists will examine the particles released from collisions of protons with liquid hydrogen and deuterium, as well as solid carbon and iron. New insights into the structure of the nucleon, which is an all-encompassing name for protons and neutrons, and the surrounding matter will answer questions about how the strong force interacts with the sea of quarks and gluons inside each nucleon. In particular, the scientists hope to learn more about the imbalance in the types of quarks discovered in a precursor experiment to SeaQuest: the decade-old NuSea experiment.

SeaQuest is housed in Fermilab’s NM4 building, located along the proton beamline in the fixed-target area. Engineering physicist Michael Geelhoed and his colleagues from the Accelerator Division are in the process of reestablishing the beamline that previously delivered protons to the KTeV experiment. A step down from the 800-GeV interactions studied by NuSea, SeaQuest will operate at a beam energy of 120 GeV. A lower energy level at a slower pace significantly increases the opportunity for scientists to see rarer processes.

The SeaQuest scientists have also recycled the 206-ton solid iron magnet from the KTeV experiment and added pieces of magnets from NuSea.

“Usually this is keeping the place nice and warm,” Argonne physicist and SeaQuest spokesperson Paul Reimer said, patting the enormous electromagnet.

SeaQuest has also borrowed magnets and chambers from other experiments at Fermilab, reducing the overall cost of the experiment.

“Our model is recycle, reduce and reuse,” Reimer said.

Much of the SeaQuest project, which is managed by the Argonne group, is funded by the Office of Nuclear Physics within the DOE Office of Science. The project also has collaborators who are funded by the National Science Foundation and, through Fermilab, it has support from DOE’s Office of High Energy Physics.

International support comes from Japan and Taiwan. The Taiwanese group has been instrumental in developing modern electronics to replace the vintage NuSea equipment, while the Japanese group plans to apply its SeaQuest experience to a similar proton experiment at J-PARC, a Japanese nuclear and particle physics facility that operates a lower-energy synchrotron accelerator.

SeaQuest will begin taking data after commissioning the experiment in mid-November.

Brad Hooker