|Monday, October 8, 2012|
ODU Physicists Help Jefferson Lab Prepare for New Era of Research
Dudek and Weinstein
Although the $310 million accelerator upgrade that is under way now at the Thomas Jefferson National Accelerator Facility in Newport News is not expected to be completed until 2014, hundreds of physicists - including 13 from Old Dominion - have already queued up to make good use of the facility's power boost.
ODU physicists also played a key role in producing a new, 65-page report that outlines just what the upgrade could mean for nuclear and particle physics research.
Of the twelve scientists from around the world who were tapped to write the visionary report - "Physics Opportunities with the 12GeV Upgrade at Jefferson Lab" - two are from ODU: Jozef Dudek, an ODU associate professor of physics who is also a staff scientist at Jefferson Lab, and Lawrence Weinstein, an ODU University Professor and Eminent Scholar of physics who conducts experiments at the lab. No other university had more than one faculty member among the project authors.
The U.S. Department of Energy is making the large investment in the upgrade in order to boost the energy of the facility's main electron accelerator from 6 billion to 12 billion electron volts, improve detector capabilities and add an experimental Hall D to the existing halls A, B and C.
Since it began operating almost two decades ago, the mile-long electron accelerator at Jefferson Lab has focused on experiments probing the fundamental structure of matter, or hadronic nuclear physics. Hadrons are composites of quarks and antiquarks and gluons held together by what is called the strong nuclear force. The protons and neutrons that form the atomic nucleus are examples of hadrons. Gluons are the mass-less particles that carry the strong force.
The report opens with an auspicious declaration: "We are at the dawn of a new era in the study of hadronic nuclear physics." It goes on to explain how the Jefferson Lab upgrade, combined with new tools in theoretical nuclear physics, will allow for more meaningful explorations of 1) the strong-force confinement and structure of hadrons, 2) the elusive spin-composition of protons and neutrons, and 3) the models and theories that now frame our understanding of nuclear and particle physics.
According to the report, answers to some baffling questions could come from Jefferson Lab in the next decade. For example, how is it that the force between two quarks becomes stronger the farther they move apart? This is just the opposite of the force holding together the nucleus and electrons of an atom and of the electromagnetic force in general. Also, what is the origin of most of the mass of the visible matter in the universe? The much-publicized Higgs Boson - strong evidence of its existence came from the Large Hadron Collider in Europe earlier this year - imparts mass to quarks, but this still leaves more than 98 percent of the mass of protons unaccounted for.
The answer to the mass quandary, many scientists believe, lies with gluons and the strong force, which is a focus of Dudek's theoretical calculations using supercomputers. His research hinges on the fundamental theory of quark and gluon dynamics that is called quantum chromodynamics (QCD). At the low-energy scales relevant for hadrons, the theory has resisted a "pen and paper" mathematical solution, while, on the other hand, a numerical approach known as Lattice QCD has proven to be a useful tool to solve the theory using controlled approximations. Over the next few years, building upon recent work done in collaboration with researchers at Jefferson Lab and others, Dudek will use Lattice QCD techniques to predict the masses and quantum numbers of hadrons, their internal quark-gluon structure, their decay into other hadrons and their couplings to photons.
"A major emphasis will be predicting properties of hybrid mesons, which are proposed exotic particles in which the usual quark-antiquark pair is accompanied by an excitation of the gluon field that binds them," Dudek said. This project will complement a planned search for hybrid mesons by the Gluonic Excitations Experiment (GlueX) in the new Hall D at the upgraded Jefferson Lab. "In the run-up to GlueX, we hope to make a number of predictions that will be experimentally tested there. It's a particularly exciting time to be doing these calculations," Dudek said.
Weinstein, who has had leading roles in experiments at Jefferson Lab probing the structure and interactions of protons and neutrons, pointed out that ODU scientists and technicians have long had a close working relationship with Jefferson Lab, and that the upgrade will strengthen those ties.
"The upgrade will build on the 20-year connection that the ODU Experimental Nuclear Physics Group has had with Jefferson Lab," Weinstein said. "We constructed a large part of its initial experimental equipment and led major elements of the scientific program. We are preparing for new leadership roles by constructing major detectors and polarized targets and leading the development of parts of the 12 GeV scientific program."
Weinstein currently leads a team from the ODU Department of Physics that is building drift chamber components for a new particle detector that will be used at Jefferson Lab after the upgrade.
"ODU faculty, staff and students have conducted some of the most important experiments at Jefferson Lab and also produced major theoretical results relevant to our research program," said Robert D. McKeown, deputy director for science at the lab.
"They continue to be leaders in the development of the future science program with the upgraded 12 GeV facility. In particular, Professor Dudek has recently made crucial theoretical contributions related to the upcoming flagship program on meson spectroscopy."
McKeown said that in addition to Weinstein's contributions on the drift chamber construction, "Professor Gail Dodge also made significant contributions to implementing and overseeing the detector construction project. These and other contributions of ODU to the future Jefferson Lab program are of great importance to the success of the Lab in the 12 GeV era."
The report that Weinstein and Dudek helped to write states that the Jefferson Lab Program Advisory Committee has already considered proposals for experiments that can be conducted at the upgraded facility. "Interest in the 12 GeV science program has been tremendous, and there are presently 52 approved proposals, each with a scientific rating and recommended allocation of beam time. This set of approved experiments will require more than six years of running the upgraded facility at near-full efficiency, extending scientific productivity well into the 2020s."
Jefferson Lab's community of researchers numbers 1,300, and they come from throughout the United States and the world. Most experiments at the facility are conducted by groups of 50-100 scientists.
The ODU Experimental Nuclear and Particle Physics Group is one of the largest and most experienced research groups working at Jefferson Lab. In addition to building major detector systems for both the original Jefferson Lab and the new upgrade, they are leaders on a wide variety of experimental programs to explore the nature of matter. They typically lead experiments that use about 10 percent of Jefferson Lab's beam time each year. Applied proportionately, that amounts to about $10 million of the $100 million in research that the lab performs annually.
In addition to Weinstein, the experimental group includes these physics faculty members: Moscov Amarian, professor; Stephen Bueltmann, assistant professor; Gail Dodge, professor; Gagik Gavalian, research assistant professor; Charles Hyde, professor; Sebastian Kuhn, Eminent Professor; and Yelena Prok, visiting assistant professor.
Dudek, who has been recognized as one of the nation's most promising young theorists, says he came to ODU in 2007 largely because of its highly respected Theoretical Nuclear and Particle Physics Group. Other than him, that group is composed of Anatoly Radyushkin, Eminent Professor; Rocco Schiavilla, Eminent Professor; Jay Wallace Van Orden, Eminent Professor; and Ian Balitsky, professor.
Last year, Dudek received an Early Career Research Award of $750,000 from the Department of Energy and earlier this year he was selected for a role in a video promoting nuclear physics, "Exploring the Heart of Matter," produced by the National Academies. More recently, he was invited to Washington, D.C., to present information about the future of Jefferson Lab research to a subcommittee of the Nuclear Science Advisory Committee charged with implementing the Long Range Plan for Nuclear Physics in the United States.