Fall 2007 Nuclear Physics Seminar Schedule |
Unless otherwise noted, the nuclear physics seminars are held on Mondays, at 2:20 p.m. in Room 307 of UTK's Nielsen Physics Building. Abstracts are included below the schedule. The UTK Physics Colloquium Schedule and ORNL Physics Division Seminar Schedule might also be of interest. Professor Witek Nazarewicz is chair of the seminar program. He may be contacted via e-mail at: witek @ utk.edu. |
Robert Grzywacz,
University of Tennessee
Rare radioactive decays - recent accomplishments and future plans
In my presentation, I will give a short overview of the research on radioactive decays of very exotic nuclei performed with participation of our group at HRIBF and NSCL and present the summary of the near term projects. The current focus is on nuclear structure and astrophysics questions near doubly magic nuclei 100Sn,78Ni and 48Ni.
Ted Barnes,
University of Tennessee/ORNL/DOE
Chaos, Confusion and Craziness:
Recent developments in the strong interactions of the charm quark
After 25 years of relative calm, the topic of hadrons containing charm quarks has seen a great surge in experimental and theoretical activity, including some remarkable new discoveries. This new era started in 2003 with the observation of very narrow charm-strange mesons at the "wrong" mass. More recent claims include a "nuclear" system containing charm-light mesons, charm-quark mesons containing valence glue, and (very recently) a possible charm-light multiquark. In this talk I will summarize the background of well-behaved charmonium (ccbar) mesons, and then review these recently discovered "charm exotica".
Geoffrey Greene,
University of Tennessee/ORNL
Why is there Matter?
The Spallation Neutron Source (SNS) at ORNL is now the most intense pulsed neutron source in the world. While most of the experimental work at the SNS will be concerned with condensed matter research, one neutron beamline will be devoted to nuclear physics. This Fundamental Neutron Physics Beamline will support a variety of experiments including a new search for a neutron electric dipole moment. This experiment will use a variety of novel techniques in an attempt to improve the experimental uncertainly on the neutron edm by two orders of magnitude. Such an improvement will have important implications for the understanding the nature of time reversal non-invariance and the origin of the cosmic matter-antimatter asymmetry. I will describe the SNS beamline, the proposed experiment, and briefly discuss the theoretical implications.
Thomas Papenbrock,
University of Tennessee/ORNL
What does 'size extensive' mean? A brief tour of the
coupled-cluster theory
Over the last few years, we have been developing coupled-cluster algorithms for nuclear structure problems. Our recent developments have given us capability to investigate weakly bound and resonant nuclei, and problems where the Hamiltonian includes a 3-nucleon interaction. I will discuss these developments and then concentrate on one aspect of coupled-cluster theory that is important for all of our calculations. That property is dubbed 'size extensivity'. A many-body theory that will properly scale from light nuclei to medium mass nuclei must maintain size extensivity. I will also describe the pitfalls of using methods that do not maintain size extensivity.
Jimmy Rotureau,
University of Tennessee/ORNL
Shell model approach for many-body open quantum systems
The theoretical description of weakly-bound or unbound atomic nuclei located in the vicinity or beyond the nucleon drip lines requires the rigorous treatment of both the many-body correlations and the continuum of scattering states and decay channels. A major theoritical challenge is the consistent description of many-body states close to particle-emission thresholds where novel properties appear, such as unusual radial features of halo states or threshold anomalies in wave functions and associated observables. The solution of the configuration-interaction problem in the presence of continuum states has been recently advanced in the real-energy continuum Shell Model(SM), the so-called Shell Model Embedded in the Continuum (SMEC) and in the complex-energy SM, the so-called Gamow Shell Model (GSM). In my talk, I will present results obtained with these two models for the two-proton emission of nuclei located beyond the proton drip line and for the structure of light nuclei located in the vicinity of the neutron drip line.
Jay Billings,
University of Tennessee/ORNL
Using Artifical Intelligence to Understand Interacting Galaxies
Interacting galaxies are crucial for the evolution of structure in the Universe, as well as for phenomena like active galactic nuclei and quasars. I will discuss our recent work applying genetic algorithms and neural networks in the optimization of galaxy collision simulations with the Gadget2 TreeSPH+N-body code. More generally, I will suggest that the combination of a genetic algorithm, neural network, and scientific computing engine could be applied to a broad range of scientific problems that exhibit complex behavior depending on many parameters, and where ascertaining quality of description is a pattern recognition issue.
Joseph Macek,
University of Tennessee/ORNL
Theory of time-dependent atomic processes
(The three-body problem in atoms and molecules)
The ionization of atoms and molecules by time-dependent external fields requires computations of electron wave functions on scales ranging from the microscopic length ~ 10-8 cm to the macroscopic length ~25 μm, or about the size of human hair. Such large variations in scale make direct computation of time-dependent processes difficult. By modifying the Schrödinger equation it is possible to treat widely varying scales so that reliable ionization cross sections for one-electron species can be computed essentially exactly. Features that emerge from such calculations will be illustrated. Progress towards benchmark calculations error ~2% will also be described.
Iain Darby,
University of Tennessee/ORNL
Proton emission in N≥82 nuclei: Recent results and future plans
The last decade has seen a wealth of data on proton emission. Recent results in the N≥82 region are leading to glimpses of the spin-isospin interaction and the effects of the pairing interaction in protons and neutrons. I will present results from Ta and Re nuclei and detail our future plans for continued study in this region.
Bob Compton,
University of Tennessee
Parity violation effects in molecules?
Following the initial observation of the fall of parity it was proposed that the, albeit infrequent, interaction of the atomic electrons with the nucleus (i.e., the exchange of virtual Zo bosons between the orbiting electrons and the quarks within the nucleus) would result in physically observable effects in the interaction of light with atoms. After considerable efforts, P-odd effects were subsequently observed in the optical activity (circular dichroism, CD, and optical rotatary dispersion, ORD) for atoms and in the occurrence of transitions between atomic hyperfine states of the same parity. These atomic physics experiments continue to play an important role in the development of the standard model of low energy nuclear physics. Weak interaction effects of the type observed for atoms have not yet been reported for molecules (e.g., CD and ORD for achiral molecules). Rather, interest in P-odd effects in molecules has focused on the energy levels of the enantiomers. This presentation will attempt to summarize the experimental efforts underway to determine the minute parity violating energy difference (PVED) between R- and S- enantiomers of a chiral molecule.
Donald Hornback,
University of Tennessee
Measurements of heavy quark production via single leptons at PHENIX
The Relativistic Heavy Ion Collider (RHIC) located at Brookhaven National Laboratory has the unique capability to collide both protons and a wide range of heavy ions at many different energies. Produced in initial hard scattering processes via gluon fusion, heavy quarks (charm and bottom) are ideal probes of such collisions. The measurement of the semi-leptonic decay of D and B mesons is a well established experimental method for investigating heavy quark production in p+p and heavy ion collisions. The PHENIX experiment possesses the capability to measure single leptons in both the electron channel at central angles and the muon channel at forward angles. These measurements have been made in wide ranging production environments at RHIC, from the single point-like QCD interactions of p+p collisions to the dense partonic fluid produced in central Au+Au collisions. Measurements in p+p permit tests of state-of-the-art pQCD calculations at sqrt(s)=200 GeV and allow for estimates of both the total charm cross section and its angular evolution. Heavy quark measurements in p+p also provide a key baseline in the so-called nuclear modification factor against which the heavy-ion single lepton measurements are quantified. The simultaneous observation of non-zero heavy quark azimuthal anisotropy and suppressed nuclear modification factor reflect the existence of a dense partonic medium in the most central Au+Au collisions. Extending the heavy quark measurements at Cu+Cu and d+Au and examining the angular dependence will provide additional insight into heavy quark production at RHIC. This talk presents the most recent PHENIX single lepton measurements and discusses our evolving understanding of heavy quark production at RHIC in terms of the current theoretical landscape.
Carl Gross,
ORNL
Magnetic moment measurements at HRIBF
Magnetic moment measurements are sensitive probes into the under lying single particle structure of the nucleus. The magnetic moment arises from the magnetic fields produced by the nucleons' charge and intrinsic spin. Each nucleonic contribution then induces the magnetic dipole moment of the state. The total moment is defined as μ= gI where I is the spin of the state and g is the gyromagnetic ratio (g factor) which can be related to the Larmor frequency of the state. In this seminar I will review two recent experiments performed at HRIBF measuring the gyromagnetic ratio of the first 2+ state in 132Te. These experiments utilized the recoil-in-vacuum and transient field techniques. I will describe the experiments and results and present a possible third technique for measuring magnetic moments with radioactive ion beams at HRIBF.
Previous Nuclear Physics Seminars