Bulletin of the American Physical Society
2010 Fall Meeting of the APS Division of Nuclear Physics
Volume 55, Number 14
Tuesday–Saturday, November 2–6, 2010; Santa Fe, New Mexico
Session MA: New Results for the r-Process |
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Chair: Christian Iliadis, University of North Carolina Room: Sweeny A |
Saturday, November 6, 2010 8:30AM - 9:06AM |
MA.00001: Observations of the r-Process in Galactic Halo Stars: Successes and Frustrations Invited Speaker: Our understanding of early Galactic nucleosynthesis was fundamentally changed in the 1980s and 1990s by the serendipitous discovery of a few stars with extremely large abundance enhancements of neutron-capture (Z$>$30) elements. Detailed spectroscopic analyses of these stars revealed their neutron-capture abundance ratios to be well-matched by the solar-system r-process-only distribution. Subsequent work has significantly sharpened our knowledge of the r-process in low-metallicity Galactic halo stars. Astronomers have found many more r-rich stars and have analyzed them in often excruciating detail; lab atomic physicists have radically altered the quantity and quality of atomic transition data; nuclear experimental physicists have improved reaction rates away from the valley of beta stability; and theoretical nuclear physicists have begun to make realistic r-process abundance predictions. Here I will summarize our observational knowledge of the r-process in stars, trying to distinguish between those results which undoubtedly will stand the test of time, and those still much in need of further development. Suggestions will be given for profitable future studies by astronomers, and requests for vital parallel investigations by physicists. [Preview Abstract] |
Saturday, November 6, 2010 9:06AM - 9:42AM |
MA.00002: Modeling r-Process Nucleosynthesis in Hot Astrophysical Flows Invited Speaker: While the basic mechanism of rapid neutron capture, or $r$-process, nucleosynthesis has long been understood, a definitive determination of the astrophysical site of the $r$ process remains elusive. Here we discuss various aspects of two potential sites---the core-collapse supernova neutrino-driven wind and hot outflows from black hole-neutron star mergers. We will pay particular attention to the role of neutrino interactions in these environments and to the importance of a careful understanding of nuclear properties far from stability for realistic $r$-process simulations. [Preview Abstract] |
Saturday, November 6, 2010 9:42AM - 10:18AM |
MA.00003: Nuclear Structure Calculations for r-Process Modeling Invited Speaker: A large number of nuclear-structure quantities, for example fission barriers, ground-state masses, beta-decay half-lives and delayed-neutron emission probabilities have been calculated in the macroscopic-microscopic FRDM model for all nuclei heavier than 16O, from the proton to the neutron drip line [1-4]. We present very briefly some essential features of the model. We discuss why we feel it can be used to reliably model properties of currently unknown nuclei. Support for this belief comes from two observations: 1) published calculated masses agree with more than 500 masses discovered after publication to even better accuracy than the agreement with masses to which the model was adjusted, and 2) a large number of nuclear properties can be modeled with a single parameter choice in a consistent fashion with good agreement with experimental data. We also show the impact on results of optimizing the single-particle spin-orbit and diffuseness parameters by presenting results of calculations based on two different choices of spin-orbit strength and potential diffuseness. We conclude by discussing recent improvements in mass model accuracy to 0.57 MeV an about 15\% improvement over the accuracy 0.669 MeV obtained in the last published model [1]. \\[4pt] [1] ADNDT 59 (1995) 185\\[0pt] [2] ADNDT 66 (1997) 131\\[0pt] [3] PRC 67 (2003) 055802\\[0pt] [4] PRC 79 (2009) 064304 [Preview Abstract] |
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