Bulletin of the American Physical Society
3rd Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 54, Number 10
Tuesday–Saturday, October 13–17, 2009; Waikoloa, Hawaii
Session 2WC: Workshop on Frontiers in Nuclear Astrophysics II |
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Chair: Hendrik Schatz, NSCL, Michigan State University Room: Kohala 4 |
Tuesday, October 13, 2009 2:00PM - 2:30PM |
2WC.00001: On the Past, Present, \& Future of 60Fe (and 26Al) Invited Speaker: The radioactive isotopes $^{60}$Fe and $^{26}$Al have been detected in the galactic plane of the Milky Way through their diffuse by $\gamma$-ray emission, on the Earth in deep sea manganese crusts, on the Moon in returned lunar samples, and in meteoritic inclusions. I will discuss the colorful history, exciting present, and future of our attempts to calibrate the nuclear astrophysics of these two radionuclides. [Preview Abstract] |
Tuesday, October 13, 2009 2:30PM - 3:00PM |
2WC.00002: Review of (n,gamma) reactions in astrophysics and scope at J-PARC Invited Speaker: A neutron capture reaction cross section of a nucleus at stellar temperatureis one of important key parameters in the construction of stellar models. A measurement of the mentioned cross section has been carried out worldwide using various neutron sources and various detectors to detect \textit{$\gamma $}-rays promptly emitted from a neutron capture reaction of a nucleus at stellar energy. I will review recent works of the neutron capture reactions of stable and/or unstable nuclei from nuclear astrophysics interest, including our recent work of the neutron capture reaction cross section measurement of $^{208}$Pb. I also discuss a new facility for a neutron capture reaction study at J-PARC. A new beam line (BL04) was constructed in the in the Materials and Life Science Facility (MLF). Two sample positions are located at 20 amd 25 m away from the spallation neutron source, where anti-Compton Ge and NaI(Tl) spectrometers are placed, respectively. An experiment to measure the cross section of minor actinide isotopes has started since last November at a proton beam power of 20 kW. [Preview Abstract] |
Tuesday, October 13, 2009 3:00PM - 3:30PM |
2WC.00003: Explosive and Neutrino Nucleosynthesis in Supernovae Invited Speaker: Supernova (SN) neutrinos play important roles for neutrino nucleosynthesis (the $\nu$-process). Light elements such as $^7$Li and $^{11}$B are mainly produced through the $\nu$-process. A part of Mn is also produced through this process in Si burning-region. The produced yields strongly depend on the luminosity and energy spectra of SN neutrinos. Neutrino oscillation also affects the yields of these elements. In this presentation, the $\nu$-process in SNe calculated using neutrino-nucleus reaction cross sections with new shell model Hamiltonians is shown. The influence of neutrino oscillation on the yields of the light elements and the dependence on mass hierarchy and the mixing angle $\theta_{13}$ will be presented. Recently, the effects of neutrino self-interaction on neutrino flavor change in SNe have been discussed. Owing to the flavor change occurring in deep region of SN ejecta, the flavor change may affect r-process nucleosynthesis. The neutrino flavor change by neutrino self-interaction in SNe is explained and the influence to r-process nucleosynthesis will be discussed. [Preview Abstract] |
Tuesday, October 13, 2009 3:30PM - 4:00PM |
2WC.00004: COFFEE BREAK
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Tuesday, October 13, 2009 4:00PM - 4:30PM |
2WC.00005: Nuclear reactions in the deep ocean and crust of neutron stars: Implications of superbursts and cooling transients Invited Speaker: Accreting neutron stars provide a fascinating natural laboratory for processes in dense matter. Over the lifetime of a neutron star accreting from a solar-mass companion, the crust, where the mass density is less than that of saturated nuclear matter, is gradually replaced with material synthesized from the accreted hydrogen and helium. The resulting compositional and thermal structure of the crust is essential input for the neutron star's magnetic field evolution, the detectability of the neutron star via gravitational wave emission from a ``mountain,'' and the strength of neutrino emissivity from the core. In this talk, I will present our current understanding of the nuclear reactions in the deep ocean and crust of accreting neutron stars; that is, at depths where the hydrogen and helium have already fused to heavier elements. In addition to highlighting recent theoretical and experimental work on these reactions, I will emphasize what observations of superbursts---rare explosions some 1000 times more energetic than regular X-ray bursts---and of cooling from neutron star transients can tell us about the thermal structure of the neutron star crust. There is one source, KS 1731$-$260, that not only exhibited a superburst, but also cooled following the apparent cessation of active accretion. There is an interesting tension between the rapid cooling, which implies a high crust thermal conductivity and hence a cool crust, and the inferred (shallow) superburst ignition depth, which requires a hot crust. I will discuss solutions to this puzzle, including a strong resonance in the $\mathrm{^{12}C} + \mathrm{^{12}C}$ cross-section. [Preview Abstract] |
Tuesday, October 13, 2009 4:30PM - 5:00PM |
2WC.00006: Standard Solar Model Data Needs Invited Speaker: The progresses in the solar neutrino experiments and the more precise determination of neutrino mass parameters by means of reactor neutrino experiment allow for the possibility to exploiting neutrinos to study the solar interior. Therefore, it will be possible to check the solar model and, more in general, to better understand the evolution of low mass stars. To reach this ambitious result it is of fundamental importance to reduce the uncertainties in solar model physics inputs. In the centre of the sun hydrogen burning is taking place, the transformation of four protons in a helium nucleus is the basic mechanism by which the Sun replaces the energy lost from the surface (which amounts to 3.82*10$^{33}$ erg s$^{-1})$. During this transformation two positrons and two neutrinos are emitted for each yielded helium nucleus. The sun is burning hydrogen mostly by means of p-p chain, the accurate knowledge of the rate of p-p chain and CNO cycle reactions at the relevant solar energy is a fundamental ingredient in the analysis of the solar neutrino experiments. In the talk I will report on the present experimental knowledge of the p-p chain and CNO cycle cross sections and how these uncertainties influence of the uncertainty the solar neutrino flux determinations. [Preview Abstract] |
Tuesday, October 13, 2009 5:00PM - 5:30PM |
2WC.00007: Neutron Sources in Stellar Carbon Burning Invited Speaker: The possibility of a high temperature s-process during the carbon burning phase in late stellar evolution depends critically on possible neutron sources. In this context the following alpha capture reactions are being discussed, $^{17}$O($\alpha $,n), $^{18}$O($\alpha $,n), $^{22}$Ne($\alpha $,n), $^{25}$Mg($\alpha $,n), and $^{26}$Mg($\alpha $,n). Their effective contribution to the neutron production depends on the abundance of the various seed nuclei, which in turn depend critically on the alpha or proton production in the $^{12}$C+$^{12}$C fusion process; it also depends on the reaction cross sections or rates of these processes at carbon burning temperatures. We have studied the reaction cross sections at low energies at the Notre Dame KN accelerator using a new $^{3}$He neutron detector array. The results will be shown and discussed in the context of late stellar evolution. In collaboration with Andreas Best, University of Notre Dame; Sascha Falahat, University of Mainz, Germany; Marco Pignatari, Keele University, UK; and Michael Wiescher, University of Notre Dame. [Preview Abstract] |
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