Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session DG: Astrophysics I: Light Nuclei |
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Chair: Michael Wiescher, University of Notre Dame Room: 105AB |
Thursday, October 27, 2011 10:30AM - 10:42AM |
DG.00001: $^8$B Breakup, the Longstanding Puzzle Muslema Pervin, Filomena Nunes The cross section of $^8$B breakup reaction provides an indirect estimate of the $^7$Be(p, $\gamma$)$^8$B reaction rate. This reaction is important because of its connection to to the solar neutrino problem. At low (stellar) energies the $^7$Be(p, $\gamma$) $^8$B reaction is dominated by the electric dipole transition (E1), while the $^8$B breakup reaction rate has a significant contribution from the quadrupole transition (E2). To obtain the astrophysical S-factor S$_{17}$(E) from different $^8$B breakup experiments we must understand the contribution of E2 to the measured observables. Previous model calculations could not provide an unambiguous estimate of E2. In our present work we use XCDCC (Extended Continuous Discretized Coupled Channel) to explore the impact of the core ($^7$Be) spin, deformation and excitation to $^8$B breakup. [Preview Abstract] |
Thursday, October 27, 2011 10:42AM - 10:54AM |
DG.00002: Search for resonant enhancement of the $^7$Be+d reaction P.D. OMalley, A. Adekola, J.A. Cizewski, M.E. Howard, S.Y. Strauss, D.W. Bardayan, K.Y. Chae, C.D. Nesaraja, S.D. Pain, M.S. Smith, S. Ahn, K.L. Jones, S.T. Pittman, K.T. Schmitt, S. Graves, R.L. Kozub, J.F. Shriner Jr., J.L. Wheeler, M. Matos, B.M. Moazen, W.A. Peters, I. Spassova $^7$Li abundances in the early universe extrapolated from observations are several standard deviations lowers than that produced by Big Bang Nucleosynthesis calculations constrained by WMAP. Since most $^7$Li is produced by the beta decay of $^7$Be, one proposed solution to this mystery is a resonant enhancement of the $^7$Be($d,p$)2$\alpha$ reaction rate via the 5/2$^+$ 16.7 MeV state in $^9$B. The $^7$Be($d,d$) reaction was done at Oak Ridge National Laboratory to search for such a resonance. This was performed in inverse kinematics using a 10 MeV $^7$Be beam and a thick CD$_2$ target. Experimental data will be shown and results will be discussed. [Preview Abstract] |
Thursday, October 27, 2011 10:54AM - 11:06AM |
DG.00003: \textit{R}-matrix Analysis of $^{16}$O Compound Nucleus Reactions R.J. deBoer, R.E. Azuma, J. Goerres, G. Imbriani, P.J. LeBlanc, E. Uberseder, M. Wiescher A large amount of experimental data exists for reactions which probe the $^{16}$O compound nucleus near the alpha and proton separation energies, the energy regimes most important for nuclear astrophysics. Difficulties and inconsistencies in \textit{R}-matrix fits of the individual reactions prompt a more complete simultaneous multiple entrance/exit channel analysis of all available reaction channels with the specific aim of attaining a consistent fitting for the $^{15}$N$(p,\gamma_0)^{16}$O cross section data. [Preview Abstract] |
Thursday, October 27, 2011 11:06AM - 11:18AM |
DG.00004: The Cross Section Measurement of the $^{14}$N(p, $\gamma )^{15}$O Reaction in the CNO Cycle Qian Li, Joachim Goerres, Richard Azuma, Richard deBoer, Gianluca Imbriani, P.J. LeBlanc, Ethan Uberseder, Michael Wiescher In stars more massive than the Sun at the hydrogen burning stage, energy is primarily generated through the CNO cycle converting four protons into one helium nucleus. $^{14}$N(p,$\gamma )^{15}$O is the slowest reaction in this cycle, thus it governs the time scale and the energy generation rate of the whole cycle. It also plays an important role for the determination of the age of globular clusters. Many groups have studied this reaction before yet their measurements and calculations lead to different astrophysical S-factors for the different primary transitions due to the uncertainties in the R-matrix fit of the reaction cross section. To get more precise results, we performed measurements of the reaction cross section over an energy range from 0.28MeV to 3.6MeV. The cross sections for the strongest transitions as well as the angular distribution of the ground state were measured using the JN/KN Van de Graaff accelerators in the Nuclear Science Lab at University of Notre Dame. R-matrix calculations have been performed using the code AZURE. The new data provide better constraints for the extrapolation of the astrophysical S-factor towards stellar energies. [Preview Abstract] |
Thursday, October 27, 2011 11:18AM - 11:30AM |
DG.00005: Measurement of the $^{17}O(p,\gamma)^{18}F$ nuclear reaction cross section in the energy range $E_{lab}=360$ - $1625$ keV Antonios Kontos, Joachim G\"{o}rres, Andreas Best, Qian Li, Daniel Sch\"{u}rmann, Ed Stech, Ethan Uberseder, Michael Wiescher, Gianluca Imbriani, Richard Azuma The $^{17}O(p,\gamma)^{18}F$ reaction influences hydrogen-burning nucleosynthesis in several stellar sites, such as red giants, asymptotic giant branch (AGB) stars, massive stars and classical novae. In the relevant temperature range for these environments ($T_{9}=0.01$-$0.4$), the main contributions to the rate of this reaction are the direct capture process, two low lying narrow resonances ($E_{R}^{lab}=70$ and $193$ keV) and the low energy tails of two broad resonances ($E_{R}^{lab}=587$ and $714$ keV). Previous measurements and calculations give contradictory results for the direct capture contribution which in turn increases the uncertainty of the reaction rate. In addition, very few published cross section data exist for the high energy region that might affect the interpretation of the direct capture and the broad resonances contributions in the lower energy range. In this work we present a measurement of the reaction at a wide proton energy range ($E_{lab}=360$ - $1625$ keV) and at several angles ($\theta_{lab}=0^{\circ},45^{\circ},90^{\circ},135^{\circ}$). All detected primary transitions and all angles were fitted simultaneously and extrapolated to lower energies using the multi-level, multi-channel R-matrix code, \emph{AZURE}. [Preview Abstract] |
Thursday, October 27, 2011 11:30AM - 11:42AM |
DG.00006: Measurement of $^{17}$F+p reactions with ANASEN Laura Linhardt, Milan Matos, B.C. Rasco, Hannah Gardiner, Kevin Macon, Jeffrey Blackmon, Daniel Santiago-Gonzalez, Lagy Baby, Evgeniy Koschiy, Ingo Wiedenhoever, Grigory Rogachev The Array for Nuclear Astrophysics Studies with Exotic Nuclei (ANASEN) is a charged-particle detector array designed primarily for studies of reactions important in the p- and rp- processes with proton-rich exotic nuclei. The first in-beam measurements with a partial implementation of ANASEN have been performed at the RESOLUT radioactive beam facility of FSU. This includes stable beam experiments and measurements of the $^{17}$F(p,p)$^{17}$F and the $^{17}$F(p,alpha)$^{14}$O reactions that are important for understanding the structure of $^{18}$Ne and the $^{14}$O(alpha,p)$^{17}$F reaction rate. The performance of ANASEN and initial results from the $^{17}$F studies will be presented. [Preview Abstract] |
Thursday, October 27, 2011 11:42AM - 11:54AM |
DG.00007: Measurement of the reactions $^{17}$O$(\alpha, \gamma)^{21}$Ne and $^{17}$O$(\alpha,$ n)$^{20}$Ne and their impact on the weak s process A. Best, J. G\"orres, M. Beard, M. Couder, R. deBoer, S. Falahat, R.T. G\"uray, A. Kontos, K.-L. Kratz, P.J. LeBlanc, Q. Li, S. O'Brien, N. \"Ozkan, K. Sonnabend, R. Talwar, W. Tan, E. Uberseder, M. Wiescher The ratio of the reaction rates of the competing channels $^{17}$O$(\alpha, \gamma)^{21}$Ne and $^{17}$O$(\alpha,$ n)$^{20}$Ne determines the efficiency of $^{16}$O as a neutron poison in the weak s process in low metallicity stars. It has a large impact on the element production, either producing elements to the mass range of A=90 in case of a significant poisoning effect or extending the mass range up to the region of A=150 if the $\gamma$ channel is of negligible strength. We present results of the first measurement of the reaction $^{17}$O$(\alpha, \gamma)^{21}$Ne and an improved study of the reaction $^{17}$O$(\alpha,$ n)$^{20}$Ne, including an independent measurement of the $^{17}$O$(\alpha,$ n$_1$)$^{20}$Ne channel, enabling a simultaneous R-Matrix fit to both the n$_0$ and the n$_1$ channels. The new data were used as input for stellar network calculations and their impact on the weak s process is discussed. [Preview Abstract] |
Thursday, October 27, 2011 11:54AM - 12:06PM |
DG.00008: Studying the 3 alpha reaction in hyperspherical harmonic approach Ngoc Nguyen In this work, the 3 alpha reaction is studied by using the Faddeev hyper-spherical harmonic (HH) method [1]. Starting from a three body model, we derive the analytical formulas for the quadrupole strength function B(E2) as well as the reaction rate which is well known for the two particles but not for three particle system. The 2+ state and the 0+ resonance are well reproduced but we consider the contributions of the nonresonant continuum states to the reaction rate in a consistent manner. Considering only Coulomb interaction for the three alpha scattering problem we can obtain analytical continuum wave functions for the 0+ states. At low temperature our calculations agree very well with NACRE and there is an expected increase in the reaction rate at high temperature due to the nuclear contribution (resonant process). A full calculation with the R-matrix method in hyper-spherical coordinate space is being done to include nuclear and coulomb in equal footing. Final results and a detail physical analysis of the reaction mechanism will be presented and compared with [2,3]. [1] I. J. Thompson, F. M. Nunes, B. V. Danilin, Comput.Phys.Comm. 161, 87-107 (2004). [2] K.Ogata, M.Kan, M.Kamimura, Prog. Theor. Phys. 122, 1055 (2009). [3] R. de Diego, E. Garrido, D.V. Fedorov, A.S. Jensen, EPL. 90, 52001(2010). [Preview Abstract] |
Thursday, October 27, 2011 12:06PM - 12:18PM |
DG.00009: Introduction to the Geometrical Standard Model of Particle Physics Kenneth Strickland, Michael DuVernois The Geometrical Standard Model (GSM) of Particle Physics is founded on the principles of a new geometrical tool, Rate Change Graph Technology (RCGT). RCGT was specifically designed to model the complexities of universal concepts. The GSM modeling tool parallels the SM with its own Rate Change Graph Mechanics yet is able to duplicate the SM structure and expand on concepts beyond the SM. RCGT uses a new methodology called geometrical intersections to increase the data available for computing and provides valuable clues as to the missing processes in current scientific practices. Forget about size and value, think geometry and in doing so peel back the layers of the physical world to see for the first time a geometrical universe. [Preview Abstract] |
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