Modern nuclear physics seeks to understand the structure of all hadronic matter. Studies of the structure of atomic nuclei now explore new regions of excitation, angular momenta, and stability that have only become accessible to detailed study through the advent of more advanced detector arrays and radioactive ion beams. The understanding of the structure of light nuclei has advanced both through modern computational techniques and effective field theories using the nucleon-nucleon force, and through intermediate energy photon and electron experiments that have illuminated the role played by mesons, baryon resonances, and the quark substructure of the nucleon in the nucleus. The baryons and mesons themselves are studied experimentally over a wide energy range with photon, neutrino, electron, meson, and proton beams, and are studied theoretically with Quantum ChromoDynamics computations, using Chiral Perturbation Theory, Lattice QCD, and perturbative QCD. Fundamental symmetries are probed in a variety of experiments, such as parity violating electron scattering from quarks in the nucleon. Indeed, modern nuclear physics now encompasses areas of research which had been considered the domain of particle physics. Our experimental nuclear physics group studies a range of these topics, with two faculty members in nuclear structure and two in intermediate energy.
The low-energy experimentalists probe nuclear structure far from stability, and In systems that exhibit unique properties by measuring electromagnetic moments, level energies, single-particle strengths and gamma-ray transitions using a variety of nuclear probes. They work closely with theorists to understand the structure of nuclei as well as nuclear reaction mechanisms, and the coupling between the two in weakly bound nuclei. 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, condensed-matter, nuclear astrophysics or stewardship science headings.
The two intermediate energy physicists, with a long history of work with hadron probes, now concentrate on experiments using photon, neutrino, electron and muon beams. These experiments try to determine basic properties of the nucleon and few-body systems, and to investigate how the nuclear environment affects the nucleon. Many of the experiments involve polarized electron beams and measurements of the polarization of recoil protons, a field in which they are world leaders.
Major low-energy nuclear physics efforts are conducted at accelerator laboratories at Yale University and Lawrence Berkeley National Laboratory and the rare isotope beam facilities at Oak Ridge National Laboratory, Michigan State University, and GANIL In France. The intermediate energy group is focused at Jefferson Laboratory in Newport News, Virginia, Fermilab in Batavia, Ilinois, and the Paul Scherrer Institute (PSI) in Villigen, Switzerland. The major facility at Jefferson Lab is CEBAF, a 12 GeV CW electron accelerator, that is the leading accelerator in the world for intermediate energy nuclear physics. The group is involved in two experiments at Fermilab, the MINERνA experiment which measures neutrino nucleus scattering, and the SEAQUEST experiment (E906) which studies the nucleon sea quark distributions and searches for dark photons. At PSI, the group is involved in an experiment to measure the proton radius.
Professor Jolie Cizewski
I am interested in studying and understanding the structure of atomic nuclei, and in particular, nuclei with many more neutrons than stable isotopes. Theoretical models predict that the shell structure that characterizes stable nuclei may be quenched in very neutron-rich nuclei. Some of these neutron-rich nuclei also lie along the path of species most likely to be populated in the rapid neutron capture process of nucleosynthesis. The studies of the properties of unstable nuclei are performed at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory in Tennessee using beams of rare isotopes. The current focus is on determining the single-neutron excitations of neutron-rich N=50 and N=82 nuclei, and probing the shell structure far from stability. The ORNL efforts are complemented by higher energy rare isotope studies at the Michigan State University National Superconducting Cyclotron Laboratory. I also serve as the Director of the Center of Excellence for Radioactive Ion Beam Studies for Stewardship Science, www.orau.org/stewardship a consortium of nuclear scientists from universities and ORNL. Earlier work involved studying highly elongated, superdeformed, excitations in heavy nuclei, the properties of nuclei near the proton drip line, and the role of dynamical symmetries and supersymmetries in understanding collective excitations in nuclei.
Professors Ronald Gilman and Ronald Ransome
Our research program for the past several years has focused on the structure of the nucleon and light nuclei, and on what happens to a nucleon in the nuclear environment. We began the new era of physics at Jefferson Lab by building on our recognized expertise in spin physics to construct the world's largest focal plane polarimeter (FPP), for Hall A, along with our colleagues at William & Mary. The FPP was used in almost half of the experiments run in the first several years of operation. It has produced particularly nice results on the electromagnetic structure of the proton in elastic ep scattering, the excitation of the proton to the Δ resonance, the structure of the deuteron in photo-disintegration at high energies, and investigating possible nucleon structure modifications in the nucleus with 4He(e,e'p). We have also been active in the polarized 3He program, investigating several aspects of 3He structure and the spin structure of the neutron, culminating in semi-inclusive deep inelastic scattering measurements of the nucleon transverse quark structure.
In addition to this rich program centered at Jefferson Lab, we have been heavily involved in two Fermilab experiments. The NuMI intense neutrino beam was commissioned in 2004 at Fermilab, opening the way to a new generation of neutrino experiments. We are founding members of the Main INjector Experiment Neutrino-A experiment MINERνA. This experiment uses a compact, fully active scintillator detector to make high precision neutrino scattering measurements. Our group has been responsible for construction of major elements of the detector and software development. The detector was completed in early 2010, with data taking and analysis ongoing since then. The Fermilab SEAQUEST experiment is an outgrowth of our nucleon structure work at Jefferson Lab. The experiment uses the Drell-Yan process, in which a beam quark and target anti-quark annihilate into a μ+μ- pair, to measure nucleon sea quark distributions. The use of nuclear targets allows access to other physics, such as quark propagation in nuclear matter and the EMC effect. Aspects of the measurement allow studies on the nucleon transverse strucure as well. Finally, we have been involved in the effort to use the Seaquest data for a new test of the existence of dark photons, in a different range of mass and coupling constant space than other current efforts. For this experiment, we have been responsible for some of the particle tracking detectors, as well as parts of the data acquisition and trigger systems. Data taking started in 2012, and has been ongoing. It is expected that starting in 2019 the experiment will be upgraded to use a polarized target.
Starting in 2012 we embarked on an effort to measure the proton radius through muon scattering, to study the proton radius puzzle. The MUSE experiment at PSI, now under construction, will take production data in 2018-2019, and will produce high precision muon scattering cross sections for the radius extraction as well positive and negative polarity comparisons for muons electrons for a measure of two-photon effects.
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, at the 88" cyclotron at the Lawrence Berkeley National Laboratory, and at the radioactive beam facility HIRBF at Oak Ridge National Laboratory.
Professor Sevil Salur
Revised April, 2017