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 FG: Astrophysics II: s-d Shell |
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Chair: Filomena Nunes, Michigan State University. Room: 105AB |
Thursday, October 27, 2011 4:00PM - 4:12PM |
FG.00001: Studying the $\alpha p$-process waiting points using Radioactive Ion Beams C.M. Deibel, M. Alcorta, P. Bertone, J. Clark, C.R. Hoffman, C.L. Jiang, B.P. Kay, H.Y. Lee, R. Pardo, K.E. Rehm, A.M. Rogers, J.M. Figueira, S. Bedoor, D. Shetty, A.H. Wuosmaa, J.C. Lighthall, S.T. Marley, M. Paul, C. Ugalde The nucleosynthetic flow in type I X-ray Bursts (XRBs) is driven by the triple-$\alpha$, $rp$ and $\alpha p$ processes. Several intermediate mass nuclei, $^{22}$Mg, $^{26}$Si, $^{30}$S, and $^{34}$Ar, have been identified as possible candidates for waiting points in XRBs. When such a nucleus is reached, the flow stalls due to ($p,\gamma$)-($\gamma,p$) equilibrium and must await $\beta$ decay unless the ($\alpha,p$) reaction is fast enough to break out of the waiting point first. A method to study these $\alpha p$-process reactions has been developed whereby the time- inverse reaction is studied in inverse kinematics using radioactive ion beams produced by the in-flight method at the Argonne National Laboratory ATLAS facility. The reactions $p$($^{29}$P,$^{26}$Si)$\alpha$, $p$($^{33}$Cl,$^{30}$S)$\alpha$, and $p$($^{37}$K,$^{34}$Ar)$\alpha$ have been studied to determine reaction rates for $^{26}$Si($\alpha,p$)$^{29}$P, $^{30}$S($\alpha,p$)$^{33}$Cl, and $^{34}$Ar($\alpha,p$)$^{37}$K, respectively. The results and possible implications for nucleosynthesis in XRBs will be discussed. [Preview Abstract] |
Thursday, October 27, 2011 4:12PM - 4:24PM |
FG.00002: Asymptotic normalization of mirror states and the effect of couplings Luke Titus, Pierre Capel, Filomena Nunes Assuming that the ratio between asymptotic normalization coefficients (ANCs) of mirror states is model independent, charge symmetry can be used to indirectly extract astrophysically relevant proton capture reactions on proton-rich nuclei based on information on stable isotopes. In this work we explore the Hamiltonian independence of the ratio between ANCs of mirror states when deformation and core excitation is introduced in the system. We apply the model to $^{8}$Li/$^{8}$B, $^{13}$C/$^{13}$N, $^{17}$O/$^{17}$F, $^{23}$Ne/$^{23}$Al, and $^{27}$Mg/$^{27}$P. Our results show that for most studied cases, the ratio between ANCs of mirror states is independent of the strength and multipolarity of the couplings induced. The exception is for cases in which there is an s-wave coupled to the ground state of the core, the proton system is loosely bound, and the states have large admixture with other configurations. We discuss the implications of our results for novae. [Preview Abstract] |
Thursday, October 27, 2011 4:24PM - 4:36PM |
FG.00003: High Precision Measurement of Resonance States in $^{18}\textrm{Ne}$ , $^{30}\textrm{S}$, and $^{38}\textrm{Ca}$ Nuclei using the (p,t) Reaction, and Reaction Rates in the $\alpha$p- and rp-Processes T. Adachi, G.P.A. Berg, E.Z. Buthelezi, J. Carter, M. Couder, R. Fearick, S.V. F\"ortsch, J. G\"orres, Y. Kheswa, J. Mira, S. Murray, R. Neveling, P. Papka, E. Sideras-Haddad, F.D. Smit, J.A. Swartz, R. Talwar, I. Usman, J.J. van Zyl, M. Wiescher, S. O'Brien Thermonuclear runaway reactions in type 1 X-ray burst are trigged by the breakout from the hot CNO cycles and is subsequently driven by $\alpha$p- and rp-processes. These time scales for the $\alpha$p- and rp-process are determined by the associated reaction rates, which depend exponentially on the associated resonance energies. High precision (p,t) measurement were preformed at iThemba LABS to examine resonance states in $^{18}\textrm{Ne}$, $^{30}\textrm{S}$, and $^{38}\textrm{Ca}$ nuclei using the K600 spectrometer with a dispersion matched beam. Preliminary analysis will be presented. [Preview Abstract] |
Thursday, October 27, 2011 4:36PM - 4:48PM |
FG.00004: Resonance strengths in $^{20}$Ne(p, $\gamma )^{22}$Na and $^{22}$Ne(p, $\gamma )^{23}$Na and the NeNa cycle Stephanie Lyons, Joachim Goerres, Antonios Kontos, Ed Stech, Michael Wiescher In second-generation stars whose stellar temperature T is greater than 0.05 GK, Hydrogen burning can proceed also via the NeNa cycle which is important for the nucleosynthesis of the Ne and Na isotopes. The stellar reaction rate for $^{20}$Ne(p,$\gamma )^{21}$Na is dominated by the Direct Capture and the high energy tail of a subthreshold resonance. The strength of these nonresonant contributions was measured [1] relative to the strength of the resonance at 1.17 MeV. Because of conflicting results for this reference [2], we have remeasured the strength of this resonance relative to the well-known 1.28 MeV resonance in $^{22}$Ne(p,g)$^{23}$Na using implanted Neon targets. In addition, we also performed an independent measurement of the $\gamma $ branching ratios and the strength of the $^{22}$Ne(p,$\gamma )$ resonance. \\[4pt] [1] C. Rolfs et al., Nuclear Physics A241, 480 (1975) \\[0pt] [2] J. Keinonen et al., Phys. Rev. C15, 579 (1977) [Preview Abstract] |
Thursday, October 27, 2011 4:48PM - 5:00PM |
FG.00005: Measurement of $^{26}$Si+p resonant elastic scattering for studying the $^{26}$Si(p,$\gamma )^{27}$P reaction Hyo Soon Jung, Y.K. Kwon, J.Y. Moon, J.H. Lee, C.C. Yun, C.S. Lee, Seonho Choi, M.J. Kim, Y.H. Kim, Y.K. Kim, J.S. Park, E.J. Kim, C.B. Moon, S. Kubono, H. Yamaguchi, D. Kahl, T. Teranishi, Y. Wakabayshi, N. Iwasa, Y. Togano, S. Cherubini Proton resonant states in $^{27}$P have been studied by the resonant elastic scattering of $^{26}$Si+p with a $^{26}$Si radioactive ion beam at 3.039 MeV/u bombarding a thick H$_{2}$ gas target with the inverse kinematics method at the low-energy RI beam facility CRIB at CNS, University of Tokyo. The properties of these resonance states are important to better determine the production rates of $^{26}$Si(p,$\gamma )^{27}$P reaction which is one of the atrophysically important reactions to understand the production of the ground state of $^{26}$Al under the explosive stellar environments at higher temperature. In this work, some new states have been observed with a high statistics and background free through a covered the range of excitation energies from E$_{x} \quad \sim $ 2.3 to 3.8 MeV. The resonant parameters of those states, were determined by an R-matrix analysis of the excitation functions. [Preview Abstract] |
Thursday, October 27, 2011 5:00PM - 5:12PM |
FG.00006: Beta-Delayed Proton- and Gamma-Decay of $^{27}$P for Nuclear Astrophysics E. Simmons, L. Trache, A. Banu, M. McCleskey, B. Roeder, A. Spiridon, R.E. Tribble, T. Davinson, P.J. Woods, G.J. Lotay, J. Wallace, D. Doherty, A. Saastamoinen The creation site of cosmic $^{26}$Al is still under debate. It is thought to be produced in hydrogen burning and in explosive helium burning in novae and supernovae, and possibly also in the H-burning in outer shells of red giant stars. Also, the reactions for its creation or destruction are not completely known. When $^{26}$Al is created in novae, the reaction chain is: $^{24}$Mg(p,$\gamma )^{25}$Al($\beta +\nu )^{25}$Mg(p, $\gamma )^{26}$Al, but it can be by-passed by another chain: $^{25}$Al(p,$\gamma )^{26}$Si(p,$\gamma )^{27}$P and it can also be destroyed directly. The reaction $^{26m}$Al(p,$\gamma )^{27}$Si* is another avenue to bypass the production of $^{26}$Al and is dominated by resonant capture. We study these resonances by an indirect method, through the $\beta $-decay of $^{27}$P. We use $^{27}$P produced and separated with MARS and a setup which allows increased efficiency for low energy protons and for high-energy gamma-rays. We measure gamma-rays and $\beta $-delayed protons emitted from states above the proton threshold in the daughter nucleus $^{27}$Si (S$_{p}$ = 7.463 MeV) to identify and characterize the resonances. Its lifetime was also measured with accuracy under 1{\%}. [Preview Abstract] |
Thursday, October 27, 2011 5:12PM - 5:24PM |
FG.00007: A new method of measuring the~$^{12}$C+$^{12}$C fusion cross sections towards astrophysical energies X. Fang, C.L. Jiang, M. Alcorta, B.B. Back, C.M. Deibel, B. DiGiovine, J.P. Greene, D.J. Henderson, R.V.F. Janssens, C.J. Lister, S.T. Marley, R.C. Pardo, K.E. Rehm, D. Seweryniak, C. Ugalde, S. Zhu, A. Alongi, B. Bucher, C. Cahillane, P. Collon, X.T. Tang, E. Dahlstrom The~$^{12}$C+$^{12}$C fusion reaction plays a crucial role in a number of important astrophysical scenarios. The past studies of carbon fusion reactions at sub-barrier energies were limited by the usage of small detectors with low efficiency. A new measurement method, particle-gamma coincidence, has been tested using Gammasphere at ANL in the center-of-mass energy range 4.0-5.0 MeV. We are building a large area silicon-detector array and a new Ge-detector array (GEORGINA) which will be coupled with the forthcoming high-current accelerator at the University of Notre Dame. Preliminary results from our test experiment will be presented. [Preview Abstract] |
Thursday, October 27, 2011 5:24PM - 5:36PM |
FG.00008: A new source of neutrons for weak s-process nucleosynthesis Brian Bucher, Justin Browne, Sergio Almaraz-Calderon, Adam Alongi, Akaa Ayangeakaa, Andreas Best, Manoel Couder, James DeBoer, Xiao Fang, Wenting Lu, Masahiro Notani, Darshana Patel, Nancy Paul, Amy Roberts, Rashi Talwar, Wanpeng Tan, Xiaodong Tang $^{12}$C($^{12}$C,n) is a potential neutron source for the weak s-process occurring in convective shell carbon burning of massive stars. This reaction has been measured only twice previously and at high energy relative to the astrophysical energy range. Recent studies at the University of Notre Dame indicate the existence of a low-energy resonance which could drastically affect the astrophysical reaction rate. The precise location of this resonance is critically important for the rate determination. A summary of our findings will be presented and the astrophysical implications will be discussed. [Preview Abstract] |
Thursday, October 27, 2011 5:36PM - 5:48PM |
FG.00009: Quarkeosynthesis -- Concise New Laws of Nuclear Physics William Webb Assume an alternate synthesis. Assume that in the building of more massive nuclei the quarks do the combining (quarkeosynthesis). Quarkeosynthesis provides concise new laws of nuclear physics. One of quarkeosynthesis' new laws is detailed. In the ``Law of Nuclear Electron Emission'' the absolute magnitude of the fractional charge ratio between outer quarks and center quark is shown to determine the electron emission decay and/or stability of a group of 183 isotopes. The Law concisely demonstrates: Isotopes with charge ratio less than 0.77 decay by emitting an electron. Isotopes with charge ratio more than 0.77 are stable. This law allows 183 simple calculations all of which unerringly lead to perfect agreement with factual nuclear data. Nuclear science has never before encountered so concise a systematic arrangement of truths showing the operation of general law. Quarkeosynthesis, the alternate synthesis, provides concise new laws of nuclear physics. [Preview Abstract] |
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