Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session L8: Nuclear Astrophysics |
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Sponsoring Units: DNP Chair: Betty Tsang Michigan State University Room: Hyatt Regency Dallas Cumberland A |
Sunday, April 23, 2006 3:15PM - 3:27PM |
L8.00001: Equation of State for low density nuclear matter Jutri Taruna, Bradley A Futch, Jorge Piekarewicz Neutron-rich matter at subnuclear densities---present in core-collapse supernovae and the crust of neutron stars---displays fascinating complex structures, such as spherical, slablike, and rodlike shapes. The equation of state and the spin-denpendent, two-body correlation function are computed via semi-classical Monte-Carlo simulations that incorporate a momentum-dependent two-body potential to simulate Pauli correlations. [Preview Abstract] |
Sunday, April 23, 2006 3:27PM - 3:39PM |
L8.00002: New Features in the Computational Infrastructure for Nuclear Astrophysics M.S. Smith, E.J. Lingerfelt, J.P. Scott, W.R. Hix, C.D. Nesaraja, H. Koura, L.F. Roberts The {\bf Computational Infrastructure for Nuclear Astrophysics} is a suite of computer codes online at {\bf nucastrodata.org} that streamlines the incorporation of recent nuclear physics results into astrophysical simulations. The freely-available, cross- platform suite enables users to upload cross sections and s-factors, convert them into reaction rates, parameterize the rates, store the rates in customizable libraries, setup and run custom post-processing element synthesis calculations, and visualize the results. New features include the ability for users to comment on rates or libraries using an email-type interface, a nuclear mass model evaluator, enhanced techniques for rate parameterization, better treatment of rate inverses, and creation and exporting of custom animations of simulation results. We also have online animations of r- process, rp-process, and neutrino-p process element synthesis occurring in stellar explosions. [Preview Abstract] |
Sunday, April 23, 2006 3:39PM - 3:51PM |
L8.00003: Beta-decay of proton-rich nucleus $^{23}$Al and astrophysical consequences Y.J. Zhai, V.E. Iacob, T. Al-Abdullah, C. Fu, J.C. Hardy, N. Nica, H.I. Park, G. Tabacaru, L. Trache, R.E. Tribble We will present the results of a $\beta$-decay study that was motivated by a nuclear astrophysics problem. For the first time $\gamma$-rays have been observed following the $\beta$ decay of pure samples of $^{23}$Al. We used the $^1$H($^{24}$Mg,2n)$^{23}$Al reaction and the MARS recoil separator of Texas A\&M University. $\beta$ and $\beta-\gamma$ coincidence measurements were made with a fast tape-transport system and $\beta$ and $\gamma$-ray detectors. The experiment allowed us to measure $\beta$ branching ratios and deduce logft values for transitions to 14 final states in $^{23}$Mg, including the isobaric analog state, and from them to determine unambigously the spin and parity of $^{23}$Al ground state to be $J^{\pi}$=5/2$^+$. We will discuss how this excludes the large increase in the radiative proton-capture cross section for the reaction $^{22}$Mg(p,$\gamma)^{23}$Al at astrophysical energies which was implied by claims that the spin and parity is $J^{\pi}=1/2^+$ [1,2], claims that motivated this study in the first place. The reaction is possible candidate to explain why space-based gamma-ray telescopes do not observe $\gamma$-rays from the decay of long-lived $^{22}$Na formed in ONe novae explosions [3]: a larger cross section would be required to divert significant flux from the A=22 into the A=23 mass chain. [1] X. Z. Cai et al, Phys. Rev. C 65, 024610 (2002). [2] H.-Y. Zhang et al., Chin. Phys. Lett. 19, 1599 (2002). [3] M. Wiescher et al., Astrophys. J. 343, 352 (1989). [Preview Abstract] |
Sunday, April 23, 2006 3:51PM - 4:03PM |
L8.00004: Proton-transfer study of unbound $^{19}$Ne states via ${}^2$H(${}^{18}$F,$\alpha$+$^{15}$O)n C.R. Brune, A. Adekola, Z. Heinen, M.J. Hornish, T.N. Massey, A.V. Voinov, D.W. Bardayan, J.C. Blackmon, C.D. Nesaraja, M.S. Smith, K. Chae, Z. Ma, A.E. Champagne, D.W. Visser, K.L. Jones, S.D. Pain, J.S. Thomas, U. Greife, R. Livesay, M. Porter-Peden, F. Sarazin, M. Johnson, C. Domizioli, R.L Kozub, B. Moazen The nuclear structure of ${}^{19}{\rm Ne}$ near the proton threshold is of interest for understanding the rates of proton-induced reactions on ${}^{18}{\rm F}$ in novae. The proton transfer reaction ${}^{18}{\rm F}(d,n){}^{19}{\rm Ne}$ has been measured by bombarding a 720-$\mu$g/cm$^2$ CD$_2$ target with a 150-MeV ${}^{18}{\rm F}^{9+}$ beam at ORNL's Holifield Radioactive Ion Beam Facility. The ${}^{19}{\rm Ne}$ states of interest near the proton threshold decay by breakup into $\alpha+{}^{15}{\rm O}$ which are detected in coincidence with position-sensitive $E-\Delta E$ Si telescopes. The reconstruction of the relative energy reveals the excited states of ${}^{19}{\rm Ne}$ which are populated. The mirror reaction ${}^2$H(${}^{18}$F,$\alpha$+$^{15}$N)p has been measured simultaneously. The implications for the ${}^{18}{\rm F}(p,\alpha){}^{15}{\rm O}$ reaction and ${}^{19}{\rm Ne}$-${}^{19}{\rm F}$ mirror symmetry will be discussed. [Preview Abstract] |
Sunday, April 23, 2006 4:03PM - 4:15PM |
L8.00005: Level structure of $^{19}$Ne from studies of the $^{17}$O($^{3}$He,$n)^{19}$Ne Reaction M.J. Hornish, C.R. Brune, S.M. Grimes, M.H. Hadizadeh, T.N. Massey, A.V. Voinov, J.E. O'Donnell, A. Adekola, Z. Heinen, C. Matei In order to better understand the incomplete level structure of $^{19}$Ne above proton threshold as it pertains to proton-induced reactions on $^{18}$F in explosive astrophysical environments, a study of the $^{17}$O($^{3}$He,$n)^{19}$Ne reaction has been performed at the Edwards Accelerator Laboratory at Ohio University. Utilizing pulsed beams and neutron time-of-flight techniques, this study has been conducted at energies where the compound reaction model is the dominant mechanism. As such, this reaction will in principle populate all excited states, including any heretofore unidentified states. This technique will enable a precise determination of excited energies for individual levels. Furthermore, the experimental differential cross section for individual states can be compared to calculations employing the Hauser-Feshbach statistical model in an attempt to extract information on the spins of the excited states. The observed $^{19}$Ne level structure from this reaction will be presented and its astrophysical implications will be discussed. [Preview Abstract] |
Sunday, April 23, 2006 4:15PM - 4:27PM |
L8.00006: Bulk Viscosity of Kaons in Warm CFL Quark Matter Matt Braby, Mark Alford, Sanjay Reddy, Thomas Schaefer We are interested in calculating the bulk viscosity of color superconducting quark matter inside neutron stars, taking into account the effects of the charged and neutral kaon modes. There have already been some calculations published calculating such transport properties as the specific heat and neutrino emissivities (Alford et al 2004, Reddy et al 2003), however a lot of the emphasis has been on calculating the bulk viscosity (Madsen 1992, Wang and Lu 1984). The bulk viscosity directly impact the dissipation of r-modes, a problem that has concerned astronomers for years. It seems quite reasonable to expect quark matter to have a different bulk viscosity than nuclear matter, so this provides a great test to distinguish between them. [Preview Abstract] |
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