Bulletin of the American Physical Society
2006 Division of Nuclear Physics Annual Meeting
Wednesday–Saturday, October 25–28, 2006; Nashville, Tennessee
Session 1WA: Pre-Meeting Workshop: Exotic Nuclei: From the Laboratory to the Cosmos I |
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Sponsoring Units: DNP Chair: David Dean, Oak Ridge National Laboratory Room: Gaylord Opryland Bayou C |
Wednesday, October 25, 2006 9:00AM - 9:30AM |
1WA.00001: Scattering and reactions in ab initio nuclear theory Invited Speaker: Over the past decade, much progress has been made toward understanding nuclei as collections of neutrons and protons, taking into account all of the complications of their interactions. Precise characterizations of the those interactions together with vast increases in computer power now allow ab initio calculations of many nuclear energy levels. Several ab initio computational methods are being pursued by different groups, and each has a distinct set of advantages and disadvantages. I will discuss the Argonne $v_{18}$ interaction, the Illinois three-body interactions, and the quantum Monte Carlo computational methods. I will describe their past successes and the efforts currently under way to apply them to nuclear scattering and reactions. These methods have significant advantages in describing unbound states, because they involve no spatial basis functions and therefore do not require recourse to specialized bases or generator coordinate methods. Our results so far include radiative capture calculations in $A=6$ and $A=7$ systems, and a set of scattering calculations for $A=5$. Our initial calculation of low-energy $^4$He-neutron scattering has been particularly successful. General single-channel scattering and electroweak capture reactions for $A\leq 12$ are within grasp, and prospects for computing nucleon-transfer cross sections are good. A truly predictive ab initio description of reactions, if we can achieve it, will be a great boon to astrophysics as a supplement to cross section data from difficult laboratory experiments and as a source of reliable information about processes not observable in the laboratory. It will also greatly expand the range of laboratory tests for the nuclear potentials. [Preview Abstract] |
Wednesday, October 25, 2006 9:30AM - 10:00AM |
1WA.00002: Measurement of the $^{17}$F + p ANC to Inform the $^{17}$F(p,$\gamma$)$^{18}$Ne Cross Section Invited Speaker: The decay of $^{17}$F, which is produced in novae by proton capture on $^{16}\!$O, is possibly the dominant Galactic source of $^{17}\!$O. However, $^{17}$F is destroyed by the $^ {17}$F(p,$\gamma$)$^{18}$Ne reaction. This reaction rate is unknown in novae environments, and is important for understanding the production of $^{17}\!$O and $^{18}$F. At typical novae temperatures, the $^{17}$F(p,$\gamma$)$^{18}$Ne rate is dominated by direct capture (DC) to bound states in $^ {18}$Ne, which is currently unmeasured due to the significant experimental challenges in performing the direct measurement. However, DC cross sections can be reliably calculated from Asymptotic Normalization Coefficients (ANCs) determined by, for example, a peripheral transfer reaction. We have measured the $^{14}$N($^{17}$F,$^{18}$Ne)$^ {13}\!$C reaction, in order to determine $^{17}$F + p ANCs, utilizing a 170 MeV beam of $^{17}$F incident on a melamine (C$_3$N$_6$H$_6$) target at the Holified Radioactive Ion Beam Facility at ORNL. Charged particles were detected in a pair of resistive strip silicon detector telescopes. Due to insufficient resolution to separate states in $^{18}$Ne by charged particle detection alone, coincident de-excitation $\gamma$ rays were measured in coincidence using the CLARION array. Details of the motivation, experiment, analysis and preliminary results will be presented. [Preview Abstract] |
Wednesday, October 25, 2006 10:00AM - 10:30AM |
1WA.00003: Reaction Studies With Light, Unstable Nuclei Invited Speaker: The availability of beams of exotic nuclei allows us for the first time to study in a terrestrial laboratory reactions, which occur in stellar explosions, such as Novae, Supernovae or X-ray bursts. In this talk I will present results from recent experiments performed with beams of light, unstable nuclei, which are produced via the in-flight technique at the ATLAs accelerator at Argonne. This work was supported by the US Department of Energy, Nuclear Physics Division, under contract No. W-31-109-ENG-38 and by the NSF Grant No. PHY-02-16783 (Joint Institute for Nuclear Astrophysics). [Preview Abstract] |
Wednesday, October 25, 2006 10:30AM - 11:00AM |
1WA.00004: Break |
Wednesday, October 25, 2006 11:00AM - 11:30AM |
1WA.00005: Determination of the $^{11}$Li charge radius Invited Speaker: Despite being discovered over 20 years ago the structure of halo nuclei is still not fully understood. One particularly important question concerns the interaction between the halo particles and the nuclear core. This has been investigated in $^{11}$Li via the measurement of the change in the nuclear charge radius between $^{11}$Li and $^{9}$Li which can be observed in a model independent way via high precision isotope shift measurements on atomic transitions. The short lifetime and necessity to isolate the small, charge radius dependent field shift from the much larger mass dependent shift requires both experimental techniques and facilities as well as atomic theory at the forefront of todays capabilities. The result of this measurements will be presented along with a discussion o fits implications on nuclear structure. [Preview Abstract] |
Wednesday, October 25, 2006 11:30AM - 12:00PM |
1WA.00006: Nuclear structure studies with fast exotic beams Invited Speaker: Observations in exotic nuclei have demonstrated that the sequence and energy spacing of single-particle orbits is not as immutable as once thought: some of the familiar magic numbers disappear and new shell gaps develop. This talk will summarize some of the recent results on the changes of shell structure in the vicinity of neutron number $N=28$ as probed with nucleon-removal reactions and inelastic scattering experiments at the NSCL. This work was supported in part by the National Science Foundation grant PHY-0110253. [Preview Abstract] |
Wednesday, October 25, 2006 12:00PM - 12:30PM |
1WA.00007: Trigger of the rp- and $\alpha $p-process Invited Speaker: X-ray bursts are driven by thermonuclear runaways in the atmosphere of accreting neutron stars. The runaway is driven by the $\alpha $p and the rp-process. These processes are triggered by the 15O($\alpha $,$\gamma )$19Ne and the 18Ne($\alpha $,p)21Na break-out reactions from the hot CNO cycles. New experimental data for the determination of these rates will be presented and the impact on the x-ray burst ignition conditions will be discussed. [Preview Abstract] |
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