Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session LD: Nuclear Physics of Supernovae and Massive Stars |
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Chair: Ani Aprahamian, University of Notre Dame Room: Hilton Kohala 3 |
Saturday, October 27, 2018 9:00AM - 9:15AM |
LD.00001: Recent Status of Core-collapse supernova Simulations from viewpoint of the microphysics Tomoya Takiwaki
Detail of core-collapse supernova mechanism is controlled by nuclear physics: nuclear equation of state(EoS), interaction between neutrinos and nuclei and nucleosyntesis. Recently significant updates are reported in this area, e.g. new EoS is provided by Togashi et al. (2017) and neutrino scattering rate on nucleons is modified by Horowitz (2017). Employment of these new models will substantially change the dynamics of shocked matter in the supernovae. In my talk, I will demonstrate the results of my simulations with updated microphysics. |
Saturday, October 27, 2018 9:15AM - 9:30AM |
LD.00002: The 12C(12C,p)23Na cross section near the Gamow energyγ Frank Strieder Carbon burning marks the ignition of the third nuclear fuel supply after H- and He-burning in the evolution of massive stars. Current estimates of carbon fusion reaction rates at astrophysical energies rely on extrapolations from higher energies. Low energy studies of 12C+12C reactions have focused either on charged particle or on γ-ray spectroscopy. Charged particle spectroscopy has the advantage that the total fusion cross section can in principle be measured, while γ-ray spectroscopy (and γ-particle coincidences) cannot account for direct transitions to the ground state of the residual nucleus and was limited at low energies due to background arising from hydrogen contamination within the target. However, the condition of being a total cross section measurement is not fulfilled in practice in the case of the particle spectroscopy due to finite energy resolution and low-energy detection limits. Recently, the Trojan Horse Method (THM) has been exploited to determine the 12C+12C cross section over the entire energy range of the Gamow window. Comparison of these results with information from newly published experiments reveal tension between THM data and direct experiments. The current status of the carbon fusion cross section and its implication will be discussed. |
Saturday, October 27, 2018 9:30AM - 9:45AM |
LD.00003: Cross Section Measurements of 84Kr(p,γ)85Rb Alicia Palmisano, Artemis Spyrou, Sean N. Liddick, Stephanie M Lyons, Alex C Dombos, Mallory K Smith, Anna Simon, Orlando Gomez, Paul A Deyoung Understanding how the p-nuclei are created is an important step in learning more about the creation of the heavy isotopes; specifically, isotopes on the proton-rich side of stability. Besides identifying the astrophysical sites, nuclear data for these isotopes along with reaction rates are crucial for accurate simulations. Sensitivity studies have marked 84Kr(p,γ)85Rb as an important reaction rate; it is a branching point between the (p,γ) and (n,γ) channels. Accurate measurements of this reaction will identify the reaction flow in this mass region and may alter the final abundances of the light p-nuclei. The 84Kr(p,γ)85Rb cross section measurement was recently performed in inverse kinematics with the ReAccelerating (ReA) facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. This was the first measurement on this reaction at astrophysically relevant energies and provided us with a stable beam to test this technique. In the future, we plan on using this technique with unstable beams where p-process cross sections have yet to be measured. Using the SuN detector and the SuNSCREEN cosmic-ray veto detector, we were able to measure the cross section at energies ranging from 2.8-3.5MeV; preliminary results will be discussed. |
Saturday, October 27, 2018 9:45AM - 10:00AM |
LD.00004: Estimating the γ-summing detector HECTOR efficiency using Geant4 Orlando J Olivas-Gomez, Craig Riengold, Anna Simon, Jack Wurzer, Joseph Arroyo, Matthew J Chamberlain, Farheen Naqvi, Artemis Spyrou, Alex C Dombos, Alicia Palmisano, Mallory K Smith, Tyler Anderson, Adam M Clark, Drew T Blankstein, Bryce Frentz, Matthew Hall, Samuel L Henderson, Xuyang Li, Shane Moylan, Patrick D O'Malley, Christopher J Seymour, Michael A Skulski Jr, Sabrina Y Strauss, Bryant J Vande Kolk, Wanpeng Tan The High Efficiency Total Absorption Spectrometer (HECTOR) is a NaI(Tl) 4π summing detector designed to measure radiative capture cross sections relevant for astrophysical processes. In a radiative capture, an excited compound nucleus de-excites via a series of gamma rays which are absorbed by the detector's scintillating array. In order to extract the cross section, the summing efficiency of the detector needs to be well understood. To determine efficiency, experimental yields are typically compared to Geant4 simulations if the level scheme and gamma-branching ratios are known. However, this technique proves to be particularly challenging for heavy nuclei, for which these quantities are not well known. We present a statistical approach in which we correlate the efficiency with the average number of segments fired in an event “multiplicity” and the total energy of the gamma cascade. Gamma cascades of 100 branching ratios are generated from a uniform distribution and are then simulated using Geant4 to determine the efficiency. As a benchmark of the procedure, the spectroscopic factors of resonances in 27Al(p,γ)28Si measured recently with HECTOR will also be presented. |
Saturday, October 27, 2018 10:00AM - 10:15AM |
LD.00005: First results from HECTOR: High EffiCiency TOtal absorption spectrometeR for p-process nucleosynthesis studies Anna Simon, Orlando Gomez, Rebeka Kelmar, Craig Reingold, Emily A Churchman, Sean Kelly, Adam M Clark, Caley Harris, Samuel L Henderson, Artemis Spyrou, Alicia Palmisano The p-process is a nucleosynthesis scenario that occurs during an explosion of a supernova that produces proton-rich isotopes of elements between Se and Hg. The p-process involves series of ($\gamma$,n), ($\gamma$,p) and ($\gamma$,$\alpha$) reactions on pre-existing s-process seed nuclei. The reactions relevant for the p-process can be studied in the laboratory via the inverse ones: the capture of protons or $\alpha$-particles. For these measurements, the High EffiCiency TOtal Absorption SpectrometeR (HECTOR) was developed at the University of Notre Dame. HECTOR is a NaI(Tl) summing detector comprised of 16 separate NaI(Tl) crystals, each read by 2 photomultipliers. The array is designed for precision cross section measurements for (p,$\gamma$) and ($\alpha$,$\gamma$). The first measurements of the (p,$\gamma$) and ($\alpha$,$\gamma$) reactions on $^{102}$Pd and $^{90}$Zr isotopes will be presented in this talk. The results will be compared to the cross sections obtained with other techniques, when available, and to the Hauser-Feshbach model calculations using the Talys code. |
Saturday, October 27, 2018 10:15AM - 10:30AM |
LD.00006: Study of the 7Be(α,γ)11C reaction with DRAGON at vp-process energies Athanasios Psaltis, Alan Chen, Devin S Connolly, Barry S Davids, Nicholas Esker, Gwenaelle Gilardy, Uwe Greife, William Huang, Dave Hutcheon, Jonathan Karpesky, Annika Lennarz, Johnson Liang, Matthew A Lovely, Som N Paneru, Rekam Giri, Chris Ruiz, Gaurav Tenkila, Alex Wen, Matthew Williams The nucleosynthesis of heavy elements at the neutrino-driven winds of core-collapse supernovae has gained a lot of attention in recent years. One of the proposed scenarios, the νp-process, can account for the production of the light p-nuclei, but it is highly sensitive to both supernova dynamics and nuclear physics input. In a recent study, it was found that the breakout from pp-chains through the 7Be(α,γ)11C reaction, which occurs prior the onset of the νp-process, can significantly influence the reaction flow, and subsequently the production of p-nuclei in the 90 <A<110 region. However, the reaction rate is poorly known over the temperature range of interest (T=1.5-3 GK). To that end, the first direct study of important resonances of the 7Be(α,γ)11C reaction with unknown strengths using the DRAGON recoil separator was recently performed at TRIUMF. The reaction was studied in inverse kinematics using a radioactive 7Be (t1/2 = 53.24 d) beam and in the first phase of the experiment two resonances above the 11C α–separation energy (Qα = 7543.62 keV) were measured. The experimental details and preliminary results from both 7Be(α,γ)11C and the benchmark 6Li(α,γ)10Β will be discussed. |
Saturday, October 27, 2018 10:30AM - 10:45AM |
LD.00007: Multimessenger signatures of the landscape of core-collapse supernovae MacKenzie Warren We have developed a new method for artificially driving core-collapse supernova explosions in 1D simulations. Turbulence is important for understanding the CCSN explosion mechanism, since turbulence may add a >20% correction to the total pressure behind the shock and thus aid in the explosion. Including turbulence results in successful explosions in spherical symmetry without altering the neutrino luminosities or interactions, as is commonly done to produce explosions in spherical symmetry. This better replicates the physical explosion mechanism and more reliably produces the thermodynamics and composition, which is vital for accurately predicting the nucleosynthesis that occurs in the supernova environment. We have applied this model to explore the multi-messenger observable signals - light curves, neutrino emission, and GW emission - for the landscape of supernova progenitors from 9 - 10 M$_{\odot}$. We have explored correlations between the underlying stellar structure and physics of the CCSNe mechanism with observable quantities. |
Saturday, October 27, 2018 10:45AM - 11:00AM |
LD.00008: Nuclear Physics Constraints on Possible Resonances in Carbon Fusion Reaction and Its Impact on Type Ia Supernovae Kanji Mori, Michael A Famiano, Toshitaka Kajino, Motohiko Kusakabe, Xiaodong Tang The 12C+12C reaction is one of the most important reactions in astrophysics. The reaction ignites type Ia supernovae (SNe Ia), which are used as a standard candle in cosmology and are the major factory of the iron group elements in galaxies. In spite of its importance, the cross sections of this reaction in astrophysical low energies have not been measured. Especially, unknown resonances in the low energy region can enhance the reaction rate and affect astrophysics. We constrain an upper limit of such resonances with the Wigner limit, and find that the astrophysical reaction rate can be enhanced by ~1000 times compared with a standard rate if they exist. We study the impact of the enhanced rate on the evolution of white dwarf-white dwarf (WD-WD) binary mergers, which is a hypothetical progenitor of SNe Ia. It is shown that ignition temperature determined by competition between cooling by neutrino emission and heating by carbon burning decreases due to the resonances. Therefore, the number of SNe Ia that comes from WD-WD mergers decreases. |
Saturday, October 27, 2018 11:00AM - 11:15AM |
LD.00009: First Direct Measurement on 56Ni(n,p) Reaction for Astrophysical Implication Hye Young Lee, Sean A Kuvin, Christiaan Vermeulen, Kevin Bennett, Eva Birnbaum, Meiring Nortier, Georgios Perdikakis, Pelagia Tsintari For the increased interest on the impact of this newly proposed nu-p process in the search of an answer to the heavy element production puzzle in core-collapse supernovae, a direct (n,p) reaction measurement is planned with the radioactive 56Ni (a half-life of 6 days) at Los Alamos Neutron Science Center (LANSCE). The radioactive 56Ni will be produced at the Isotope Production Facility at LANL by irradiating 55-75 MeV protons with about 250 microA current on a 59Co foil through the (p,4n) reaction channel. We are investigating the chemical separation procedure for achieving a pure Ni radioactive target with required uniformity for (n,p) reaction studies. For handling a highly radioactive target and performing nuclear reaction studies with charged particle detectors under high radiation, we are developing an optimized detection system using a GEANT simulation and in-beam background measurements at LANSCE. The progress on this effort and the outlook for upcoming LANSCE experiments will be presented.
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(Author Not Attending)
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LD.00010: Multidimensional Simulations of Energy Transport via Convection and Gravity Waves Driven by Core Neon and Oxygen Nuclear Burning in Massive Stars Jennifer Ranta, Sean Couch Progenitors of core-collapse supernovae are now expected to undergo extreme mass loss events as pre-SN outbursts. In this work, two-dimensional simulations of massive stars of 9 different masses ranging from 15-34M$_{\odot}$ were performed to study the transport of energy in the inner regions of these SN progenitors during the neon/oxygen core burning phase of stellar evolution. This epoch of nuclear burning is consistent with timing estimates of some of these pre-SN mass loss events (approximately 1-3 years prior to SN event). The core heating caused by this neon/oxygen burning drives large-scale convection and subsequent gravity waves that propagate through the star carrying the energy released from the nucleosynthesis in the core. These simulations realistically simulate this energy generation and transport through the inner convective and radiative stellar regions and examine the potential for this nuclear burning epoch to create convection and gravity waves energetic enough to result in enhanced mass loss events in massive SN progenitor stars. |
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