Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session J17: Nuclear AstrophysicsOn Demand
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Sponsoring Units: DNP Chair: Jeffrey Blackmon, Louisiana State University Room: Delaware A |
Sunday, April 19, 2020 1:30PM - 1:42PM |
J17.00001: The $^7$Be($\alpha,\gamma$)$^{11}$C Reaction Rate and Its Contribution to the Evolution of Population-III Stars Eric Aboud In the early stages of their lives, zero-metallicity stars undergo the proton-proton process until enough $^{12}$C is produced to start the CNO cycle. Due to the high energies needed for the main $^{12}$C production method (triple $\alpha$ process), low-mass main-sequence stars may not produce $^{12}$C before they collapse. The theoretical hot proton-proton chain may provide an alternate method through reaction chains. The specific chain of interest is the $^7$Be($\alpha,\gamma$)$^{11}$C(p,$\gamma$)$^{12}$N($\beta^+,\nu$)$^{12}$C reaction chain. Theoretical studies have hinted at the large contribution of the sub-alpha threshold state in $^{11}$C to the reaction rate. A detailed study of the $^7$Be($\alpha,\gamma$)$^{11}$C reaction rate, using the analog $^7$Be($^6$Li,$d\gamma$)$^{11}$C transfer reaction, is being performed. The present work aims to experimentally determine the contribution of the sub-alpha threshold state to the reaction rate for the first time. [Preview Abstract] |
Sunday, April 19, 2020 1:42PM - 1:54PM On Demand |
J17.00002: New Constraints on Sodium Production in Globular Clusters From the $^{23}$Na$(^3$He$,d)^{24}$Mg Reaction Caleb Marshall, Kiana Setoodehnia, Federico Portillo, Richard Longland Globular clusters consist of hundreds of thousands of stars gravitationally bound in a relatively small radius. Over the last few decades, intense observational study has revealed that globular clusters are comprised of multiple stellar populations each with distinct chemical signatures. The star-to-star Na-O anticorrelation is the most pervasive of these so called abundance anomalies, and is theorized to be the result of stellar material undergoing hydrogen burning at $50 \text{-} 100$ MK. Unfortunately, many thermonuclear reaction rates suffer from large uncertainties at these temperatures, thereby limiting our understanding of nucleosynthesis in globular clusters. Among these rates one of the most critical is the sodium destroying reaction $^{23}$Na$(p, \gamma)^{24}$Mg. Using the Enge Split-pole Spectrograph at Triangle Universities Nuclear Laboratory (TUNL), we have measured the transfer reaction, $^{23}$Na$(^3$He$,d)^{24}$Mg. Several novel analysis techniques have made it possible to extract excitation energies, spin-parities, and spectroscopic factors with realistic uncertainties. These uncertainties have been propagated through to $^{23}$Na$(p, \gamma)$ reaction rate, thereby improving our understanding of sodium destruction in stellar material. [Preview Abstract] |
Sunday, April 19, 2020 1:54PM - 2:06PM |
J17.00003: Supernova Neutrino-process nucleosynthesis with neutrino self-interaction and MSW effects Grant Mathews, Heamin Ko, Myung-Ki Cheoun, Eunja Ha, Motohiko Kusakabe, Takehito Hayakawa, Hirokazu Sasaki, Toshitaka Kajino, Masa-Aki Hashimoto, Masaomi Ono, Mark Usang, Satoshi Chiba, Ko Nakamura, Alexey Tolstov, Kenichi Nomoto, Toshihiko Kawano The $\nu$-process is a unique nucleosynthesis mechanism that only affects the abundances of some rare nuclei. There are, however, uncertainties due to the neutrino mass hierarchy, neutrino oscillations and the neutrino self-interaction. In this talk we discuss calculations of the abundances of $^7$Li, $^{11}$B, $^{92}$Nb, $^{98}$Tc, $^{138}$La, and $^{180}$Ta produced by the $\nu$-process. We consider the modification both by the $\nu$ self- interaction near the neutrinosphere and the Mikheyev-Smirnov-Wolfenstein effect in the outer layers based upon time-dependent neutrino energy spectra from core-collapse supernova simulations. Abundances of $^7$Li and heavy isotopes $^{92}$Nb, $^{98}$Tc and $^{138}$La are reduced by a factor of $\sim 2$ by the $\nu$-self-interaction. In contrast, $^{11}$B is relatively insensitive. We find that the abundance ratio of heavy to light nuclei, $^{138}$La/$^{11}$B, is a robust probe of the neutrino mass hierarchy, and the normal mass hierarchy is more likely to be consistent with the solar meteoritic abundances. [Preview Abstract] |
Sunday, April 19, 2020 2:06PM - 2:18PM On Demand |
J17.00004: Nuclear Reactions Important for Astrophysics from \textit{Ab Initio} Theory Petr Navratil, Guillaume Hupin, Kostas Kravvaris, Anna McCoy, Callum McCracken, Sofia Quaglioni, Matteo Vorabbi In recent years, significant progress has been made in \textit{ab initio} nuclear structure and dynamics calculations employing Hamiltonians constructed within chiral effective field theory. We have developed an approach, the No-Core Shell Model with Continuum (NCSMC) [1,2], capable of describing both bound and unbound states in light nuclei in a unified way. We will discuss applications of NCSMC to nuclear reactions important for astrophysics and present results for the neutron radiative capture reactions $^{\mathrm{8}}$Li(n,$\gamma )^{\mathrm{9}}$Li and $^{\mathrm{14}}$C(n,$\gamma )^{\mathrm{15}}$C, for the proton radiative capture reactions $^{\mathrm{11}}$C(p,$\gamma )^{\mathrm{12}}$N and $^{\mathrm{7}}$Be(p,$\gamma )^{\mathrm{8}}$B as well as for the $^{\mathrm{3}}$He($\alpha \gamma )^{\mathrm{7}}$Be radiative alpha capture. The $^{\mathrm{7}}$Be(p,$\gamma )^{\mathrm{8}}$B and $^{\mathrm{3}}$He($\alpha \gamma )^{\mathrm{7}}$Be reactions in particular play a role in Solar nucleosynthesis and neutrino physics and have been subject of numerous experimental investigations including ongoing measurements at TRIUMF.~Finally, we will highlight our recent calculations hinting at a possible near-threshold $S$-wave resonance in $^{\mathrm{6}}$He$+$p [3] that might have implications for astrophysics. [1] S. Baroni, P. Navr\'{a}til, and S. Quaglioni, PRL \textbf{110}, 022505 (2013). [2] P. Navr\'{a}til, S. Quaglioni, G. Hupin, C. Romero-Redondo, A. Calci, Phys. Scr \textbf{91}, 053002 (2016). [3] M. Vorabbi, P. Navr\'{a}til, S. Quaglioni, G. Hupin, PRC \textbf{100}, 024304 (2019). [Preview Abstract] |
Sunday, April 19, 2020 2:18PM - 2:30PM On Demand |
J17.00005: Sandblasting The R-process From A NSNS Event Xilu Wang, Brian Fields, Matthew Mumpower, Trevor Sprouse, Rebecca Surman, Nicole Vassh Neutron star mergers are r-process nucleosynthesis sites, which eject materials at high velocity ranging from 0.1c to as high as 0.6c. Therefore the r-process nuclei ejected from a neutron star merger event are sufficiently energetic to initiate spallation reactions with the interstellar medium particles. The spallation reactions tend to shift the abundance pattern to lower masses and smooth the abundance shape, thus “sandblasting” the r-process abundance pattern towards solar data. The spallation effects depend on both the initial r-process nuclei conditions, which is determined by the astrophysical trajectories and nuclear data adopted for the nucleosynthesis calculations, and the propagation process with various initial ejecta velocities and spallation cross-section values. [Preview Abstract] |
Sunday, April 19, 2020 2:30PM - 2:42PM On Demand |
J17.00006: Quarkyonic Matter Equation of State in Beta-equilibrium. tianqi zhao Quarkyonic matter as a crossover transition from uniform nuclear matter to asymptotic free quark sea could exist in the core of neutron star. Baryons in this model are viewed as triple pair of quarks at Fermi surface. We build quarkyonic matter equation of state consists of with realistic asymmetric nuclear matter, 2-flavor quarks and leptons. We discover that quarkyonic matter has higher lepton fraction(Ye) than uniform nuclear matter(npeu) under beta-equilibrium. As a consequence, direct Urca process is allowed around 2 to 4 times saturation density. [Preview Abstract] |
Sunday, April 19, 2020 2:42PM - 2:54PM On Demand |
J17.00007: Axion cooling of neutron star mergers Steven Harris, Mark Alford, Jean-Francois Fortin, Kuver Sinha Axions may be produced in nuclear matter via neutron-neutron bremsstrahlung. We calculate the mean free path of axions in neutron star merger conditions, and find that axions created in a merger would free-stream through it, leading to cooling of the merger. We calculate the emissivity of axions over a wide range of temperatures, densities, and axion-neutron coupling constants, and translate that into a characteristic cooling time due to axion emission. We find that in certain thermodynamic conditions, axion emission could cool nuclear matter in timescales less than ten milliseconds, which makes axion cooling relevant for neutron star mergers. [Preview Abstract] |
Sunday, April 19, 2020 2:54PM - 3:06PM On Demand |
J17.00008: Exponentials and Hexagon Rings Provide Many Equations for Constants, Astronomical Patterns, Electron Orbits, Gravity, and Contributions to a Theory of Everything. Rob Allen Exponentials and hexagon ring properties accurately calculate force ratios, particle masses, and constants from quarks to cosmic scales. Masses of many particles from muons to the Higgs form patterns resembling tables of aromatic hexagon compounds. Slides show induction patterns from the COBE Big Bang scale down to electron orbits with common mathematics from rings. A few examples follow. The integer number of electron masses in a proton and antiproton pair=3672=6X6X6X(6X6/2-1). A muon/electron mass=206.77=(6X3-1)X6X2 +natural log of (6X3-2). The Higgs mass/electron is about 244794=((6X3-1)X4)X6X6X(6+4)X(6+4)-6. C is speed of light and the Stephan-Boltzmann Constant=17/C=(6X3-1)/C. The Inverse Fine Structure Constant=137.036=6X6+(6+(6-2))X(6+(6-2))+1+(6X6/((6+(6-2))X(6+(6-2))X(6+(6-2)))). Electromagnetism/Gravity between a positron and an electron=(((6X3-1)X(6X3-2)+1))^(6X3-1)X(6X3-2)X(1+(1/(6X6X6X(6-1)/2- 6/2))).\par Rob L. Allen, pioneered and improved many instrumentation systems. He has a BS Degree in Computer Science from Stephen F Austin University. Management included computer centers, research groups, and allocating funds to universities. He initiated and convinced Howard Keck (CEO over Rob) to fund the Keck Telescopes. [Preview Abstract] |
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