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The definition of nuclear physics has expanded in recent years and now encompasses areas of research which had been considered the domain of particle physics: Nuclear physics can now be considered the physics of the nucleus and the physics of the nucleon. Traditional nuclear structure studies explore new regions of excitation, angular momenta, and stability that have become accessible to detailed study through the advent of more advanced detector arrays and radioactive ion beams. Our experimental nuclear physics group includes two faculty members in nuclear structure and three in intermediate energy.
The low-energy experimentalists probe nuclear structure at the limits of angular momenta, stability, and elongation, by measuring electromagnetic moments, level energies, and gamma-ray transitions using a variety of nuclear probes. There is a special interest in the identification and characterization of heavy-mass nuclei with large quadrupole deformations. Aspects of this program also study the transitional nuclei, near the onset of collective motion. This group has also been noted for their broad range of interests, many of which are only peripherally related to standard nuclear physics, but could more appropriately appear under the atomic physics or condensed-matter heading.
The three intermediate energy physicists, with a long history of work with hadron probes, are now concentrating on experiments using electron beams. These experiments will try to determine basic properties of the nucleon and few-body systems, and to investigate how the nuclear environment affects the nucleon. Most of the experiments involve polarized electron beams and measurements of the polarization of recoil protons, a field in which they are world leaders.
Major nuclear structure efforts are located at the Argonne and Lawrence Berkeley National Laboratories, and at the Yale University accelerator laboratory. The intermediate energy group is focused at Jefferson Laboratory (TJNAF) in Newport News, Virginia. The major facility there is CEBAF, a new 5.5 GeV CW electron accelerator that is now the leading accelerator in the world for intermediate energy nuclear physics. They also carry out some experiments at MAMI, an 855 MeV continuous electron beam facility at the University of Mainz in Germany.
Professor Jolie Cizewski
My research efforts are focused on the study of excitations in atomic nuclei near the limits of stability and angular momentum. Nuclei far on the neutron-deficient side of stability can decay by emitting a proton. We have studied nuclei near and beyond the proton-drip-line in the mass-170 region. In addition we have been involved in studies of very heavy nuclei, which would be unbound to spontaneous fission if not for corrections to the binding energies from the shell structure. Both of these studies have shown the weakly bound nucleus to be surprisingly robust, and able to sustain rather large amounts of angular momentum and excitation energy. Experiments are conducted at nuclear laboratories around the world, including the national laboratories at Argonne and Berkeley. Future plans are to participate in radioactive ion beam facilities at Oak Ridge and Argonne National Laboratories.
Professors Ronald Gilman, Charles Glashausser, and Ronald Ransome
We have begun the new era of physics at TJNAF by building on our recognized expertise in spin physics developed primarily at LAMPF (Los Alamos) and SATURNE (Paris). The largest focal plane polarimeter (FPP) ever built was designed and constructed at Rutgers and William & Mary and is now operating in the hadron spectrometer in Hall A at Jefferson Lab. This FPP will be used in almost half of the experiments approved for this experimental area. One of these, for which Rutgers is the leading group, is part of the commissioning experiment for the Hall that will run in Summer, 1997. We will measure the ratio of the electric and magnetic form factors of the proton in the nuclear medium by measuring the polarization of protons knocked out of 16O by the incoming electron. A related experiment will run soon at Mainz. The ratio of these form factors for the free proton will be measured in experiments scheduled for Spring, 1998. Polarization measurements proposed by us in the breakup of the deuteron by incident photons will determine whether this reaction is indeed dominated by the simple quark structure of the nucleon as cross section measurements suggest. We are currently running on the first major experiment at TJNAF, a measurement of the tensor polarization in the elastic scattering of electrons from deuterium, in Hall C. This experiment is also designed to see the effects of the quark structure of the nucleons in deuterium. These are examples of the rich program we are embarking upon in the lively physics atmosphere provided by the new laboratory.
Professor Noémie Koller
The electromagnetic properties of low-lying nuclear states are very sensitive indicators of the underlying nuclear structure, and in particular, of the interplay between single particle and collective excitations which have been found to coexist even at very low energies. We carry out experiments designed to measure the magnetic dipole and electric quadrupole moments of very short lived, high spin, nuclear states, and of exotic nuclei far-from-stability. Radioactive beam facilities are being planned in the US which will produce abundant quantities of nuclei that are likely to display "new physics" highlighted by very different p-n interactions, different spin-orbit couplings and coexistence of rather exotic shapes. These experiments rely on the hyperfine interactions between the nuclei and the solid environment in which they are embedded. Thus, in addition to providing direct nuclear structure data, these experiments lead to detailed information on the fundamental interactions between ions and magnetic and non-magnetic solids. Experiments are performed at the Tandem Accelerator at Yale University and at the 88" cyclotron at the Lawrence Berkeley National Laboratory.
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Revised November, 2000