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 KG: Nuclear Astrophysics II |
Hide Abstracts |
Chair: Toshio Suzuki, Nihon University Room: Kings 2 |
Saturday, October 17, 2009 9:00AM - 9:15AM |
KG.00001: Determination of Gamow-Teller Strength Distributions and Electron Capture Rates for pf-shell Nuclei in Pre-supernova Stars Arthur L. Cole, Remco G.T. Zegers, B. Alex Brown, G. Wesley Hitt, LeShawna Uher Modeling the evolution of pre-supernova stars and their collapse requires determining the electron capture rates for pf-shell nuclei. We intend to systematically calculate Gamow-Teller strength B(GT) distributions for all pf-shell nuclei and present preliminary result for the initial calculations. Calculations will be performed with a shell-model code using at least two different interaction Hamiltonians to describe the interaction between the nucleons in the nuclei undergoing electron capture. The resulting B(GT) distributions were used to calculate the corresponding electron capture rates at stellar temperatures and densities relevant to pre-supernova core collapse stars. Calculated B(GT) distributions are compared to experimental measurements if they exist. [Preview Abstract] |
Saturday, October 17, 2009 9:15AM - 9:30AM |
KG.00002: Very low energy protons from $\beta $-delayed p-decay of proton-rich nuclei for nuclear astrophysics E. Simmons, L. Trache, A. Banu, J.C. Hardy, V.E. Iacob, M. McCleskey, B. Roeder, A. Spiridon, R.E. Tribble, T. Davinson, G. Lotay, P.J. Woods, A. Saastamoinen, J. Aysto We developed a technique to measure very low energy protons from the beta-delayed proton-decay of proton-rich nuclei produced and separated with the MARS recoil separator at TAMU. A simple setup consisting of a telescope made of a thin double sided Si strip detector (p-detector) backed or sandwiched between two thick Si detectors ($\beta $-detectors) was designed. The source nuclei are slowed down from 30-40 MeV/u and implanted in the middle of the thin p-detector. The excited states populated in daughter nucleus above the proton threshold are resonances in the radiative proton capture leading to that nucleus; therefore, beta-decay can be a useful mechanism to study these resonances. In particular, we have studied $^{23}$Al and $^{31}$Cl and got information on the resonances of $^{22}$Na(p,$\gamma )^{23}$Mg and $^{30}$P(p,$\gamma )^{31}$S reactions, both important in novae. We studied different W1 and BB2 p-detectors, 45-140 $\mu $m thick, made by MSL, and found that thinner detectors with a small cell size are best to measure proton energies as low as 2-300 keV. [Preview Abstract] |
Saturday, October 17, 2009 9:30AM - 9:45AM |
KG.00003: Beta-decay measurement of $^{46}$Cr Y. Wakabayashi, H. Yamaguchi, T. Hashimoto, S. Hayakawa, Y. Kurihara, D.N. Binh, D. Kahl, S. Kubono, S. Nishimura, Y. Gono, M. Suga, Y. Fujita For the rapid proton capture process ($\it{rp}$-process) in X-ray bursts and the core-collapse stage of supernovae, proton-rich $\it{pf}$-shell nuclei far from the line of stability play important roles. Studies of the feeding ratios and half-lives of the $\beta$ and electron capture decays of these proton-rich $\it{pf}$-shell nuclei are of great astrophysical interest not only for nucleo synthesis but also for Fermi and Gamow-Teller transition study. The experiment to measure the half life of $\beta$ decay of $^{46}$Cr was performed using the low-energy RI beam separator (CRIB) of the Center for Nuclear Study (CNS), University of Tokyo. The $^{46}$Cr particles were produced by the $^{36}$Ar + $^{12}$C fusion reaction. A natural C foil of 0.56 mg/cm$^{2}$ was installed as the primary target. The $^{36}$Ar primary beam was accelerated up to 3.6 MeV/nucleon by the RIKEN AVF cyclotron. A double sided Si strip detector (DSSD) of 500-$\mu$m thickness was used as a $\beta$-ray detector. A Si detector of 1.5-mm thickness was placed just behind the DSSD for a $\beta$-ray detector. To measure $\beta$-delayed $\gamma$ rays, 3 clover and 1 coaxial Ge detectors were set around the target chamber. The beam was pulsed to measure the half life of the $\beta$ decay of $^{46}$Cr. The $\beta$-delayed $\gamma$ ray of $^{46}$Cr was observed in this experiment. The experimental result will be discussed. [Preview Abstract] |
Saturday, October 17, 2009 9:45AM - 10:00AM |
KG.00004: Re-measuring the half-life of $^{60}$Fe Philippe Collon, Andreas Stolz, Sam Austin, Manoel Couder, Irshad Ahmad, John Greene, Daniel Robertson, Chris Schmitt, Matt Bowers, Wenting Lu, Kirk Post, Michael Carilli A recent experiment both at PSI and at Munich on the $^{60}$Fe lifetime points to a T$_{1/2}$ for $^{60}$Fe that is possibly 70{\%} higher (i.e. $\sim $2.6x10$^{6}$ years) than the presently accepted value (1.5x10$^{6}$ years). $^{60}$Fe is mainly produced in core collapse supernovae explosions and these new results open up a number of questions as many factors scale with this number; from the $^{60}$Fe abundance determination with gamma ray telescope measurements to recent $^{60}$Fe(n, $\gamma )$ cross section studies. We are presently working on a double-pronged attempt at re-measuring this half-life using the ``old'' AMS technique used by the Kutschera group in 1984 as well as a low-background activity measurement on the growth of $^{60}$Co from the decay of $^{60}$Fe. Both rely however on a clean production of a $^{60}$Fe sample as measurements rely on measuring the $^{60}$Co decay $\gamma $-line from $^{60}$Co produced by the decay of $^{60}$Fe. Beam time was made available at the NSCL to produce a well characterized $^{60}$Fe sample at the focal plane of the A1900. The $^{60}$Fe ions were implanted in a high purity Al target. We will report the results from this run as well as from the chemical separation of the $^{60}$Fe and first measurements of the sample. [Preview Abstract] |
Saturday, October 17, 2009 10:00AM - 10:15AM |
KG.00005: Spallation process by weakly interacting charged massive particle in nucleosynthesis Kenichi Sugai, Joe Sato, Kazunori Kohri, Koichi Yazaki, Masafumi Koike, Masato Yamanaka, Toshifumi Jitto Recent result from WMAP suggests the possible deficit of the abundance of the lithium in the universe. We note that this deficit can be accounted for by Supersymmetric extentions of the Standard Model of the elementary particles. The abundance of lithium 6 has been considered in these models, but without taking account of any nuclear spallation process caused by a Supersymmetric particle. In this work we calculate a rate of the spallation to evaluate the abundance. [Preview Abstract] |
Saturday, October 17, 2009 10:15AM - 10:30AM |
KG.00006: New Precision Mass Measurements of Heavy $^{252}$Cf Fission Fragments Near the $r$-Process Path J. Van Schelt, G. Savard, S. Caldwell, M. Sternberg, J.A. Clark, J.P. Greene, A.F. Levand, T. Sun, B.J. Zabransky, J. Fallis, K.S. Sharma, D. Lascar, R.E. Segel, G. Li Precision mass measurements of nuclides near the astrophysical $r$-process path are vital to reduce the uncertainties in the relevant neutron separation energies given by mass models, and the consequent abundance predictions. As part of an ongoing program, the Canadian Penning Trap mass spectrometer at Argonne National Laboratory has measured the masses of fission products from a $^{252}$Cf source in a large-volume gas catcher. This has produced 38 new mass measurements of neutron-rich nuclides ranging from $Z=51$ to $64$, many closer to the $r$-process path than had previously been measured for these elements. Systematic deviations from the AME 2003 are seen over a wide range of elements. The program of mass measurements will continue at the CARIBU upgrade to the ATLAS accelerator at ANL this fall. [Preview Abstract] |
Saturday, October 17, 2009 10:30AM - 10:45AM |
KG.00007: New experimental studies of the production of 44Ti Daniel Robertson, Philippe Collon, Joachim Goerres, Michael Wiescher, Hans Werner Becker The main production reaction of 44Ti observed in core collapse supernovae is the 40Ca($\alpha $,$\gamma )$44Ti reaction. A number of different experimental studies have been performed over the last years to determine the stellar reaction rate. These measurements were based on in-beam gamma spectroscopy techniques, accelerator mass spectrometer (AMS) techniques, and inverse reaction techniques with a recoil separator for separating and detecting the reaction products. The experimental results showed drastic differences. New experiments have been performed at the DTL Bochum and at the NSL Notre Dame using gamma spectroscopy and AMS techniques, respectively to investigate the reaction and the present discrepancies in the predictions. The results of the experiments will be presented and the impact on the reaction rate will be discussed. [Preview Abstract] |
Saturday, October 17, 2009 10:45AM - 11:00AM |
KG.00008: Pycnonuclear fusion in the curst of accreting neutron stars Mary Beard, Edward Brown, Leandro Gasques, Rita Lau, Hendrik Schatz, Michael Wiescher, Dimitrji Yakovlev Pycnonuclear fusion processes take place at extreme density conditions of $\rho >$10$^{10}$ g/cm$^{3}$, anticipated for the core of white dwarfs or the crust of neutron stars. A formalism was developed for predicting pycnonuclear reaction rates for neutron rich nuclei in the carbon to magnesium range. The reaction rates have been used to simulate pycnonuclear burning in the deeper crust of an accreting neutron star. The pycnonuclear reaction rates will be presented and the results of the nucleosynthesis simulations will be discussed. [Preview Abstract] |
Saturday, October 17, 2009 11:00AM - 11:15AM |
KG.00009: Effect of Long-lived Strongly Interacting Relic Particles on Big Bang Nucleosynthesis Motohiko Kusakabe, Toshitaka Kajino, Takashi Yoshida, Grant Mathews Some particle theories beyond the standard model predict that relic long-lived strongly interacting massive particles (SIMPs or X particles) could exist in the early universe. We study effects of such long-lived SIMPs on big bang nucleosynthesis (BBN). The interaction strength between an X particle and a nucleon is assumed to be similar to that between nucleons. We then calculate BBN in the presence of the unstable neutral charged X0 particles taking account of the capture of the X0 particles by nuclei to form X-nuclei. We find that SIMPs form bound states with normal nuclei during a relatively early epoch of BBN. This leads to the production of heavy elements. Constraints on the abundance of X0 particles are derived from observational limits on the primordial light element abundances. Particle models including long-lived colored particles with lifetimes longer than 200 s are rejected based upon these constraints. [Preview Abstract] |
Saturday, October 17, 2009 11:15AM - 11:30AM |
KG.00010: Mass, Energy, Space And Time Systemic Theory ---MEST--- repulsion and gravity Dayong Cao Things have their physical system of the mass, energy, space and time of themselves-MEST. Sun can give the planets the repulsion and the gravity. It decided the relationship between the mass-energy and space-time of the planets. The repulsion of the planets ``equal'' its gravity. So them get a balanceable system and a inertial system. The planets lie in the wave like the boat being in the water. When sun radiate light, it can produce the repulsion. It decided the relationship between the mass-energy and space-time of the radiate light. When the radiate light condense to the condensed light (gravity wave), and it come back to the sun. It can produce the gravity. It decided the relationship between the mass-energy and space-time of the gravity wave. Both of the radiate light and the gravity wave act on the planets. There are their physical model which is about their mass-energy relation and their mass-energy wave equation. In the solar system, there are a lot of the dark matter-energy (wave) which is from the black hole. The dark matter-energy would go into the solar system and could give the sun the press force like the gravity. In sun, sun's nuclear fusion can produce repulsion. Sun is control nuclear fusion. It is controlled by the dark matter-energy. [Preview Abstract] |
Saturday, October 17, 2009 11:30AM - 11:45AM |
KG.00011: Entropy growth in the early universe and confirmation of initial big bang conditions (Why the quark-gluon model is not the best analogy) Andrew Beckwith This paper shows how increased entropy values from an initially low big bang level can be measured experimentally by counting relic gravitons. Furthermore the physical mechanism of this entropy increase is explained via analogies with early-universe phase transitions. The role of Jack Ng's revised infinite quantum statistics in the physics of gravitational wave detection is acknowledged. Ng's infinite quantum statistics can be used to show that $\Delta S\approx \Delta N_{gravitons}$ is a starting point to the increasing net universe cosmological entropy. Furthermore, we compare the increase in relic gravitons with ``chilled neutrinos'' generated as of at the start of the pre CMBR era, before CMBR ``turned on'' roughly 400 thousand years after the big bang. [Preview Abstract] |
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