Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session PD: Nuclear Astrophysics VIII |
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Chair: Andrea Richard, MSU Room: The Loft |
Thursday, October 14, 2021 9:30AM - 9:42AM |
PD.00001: Beam contaminants reduction for experiments with St. George Ruoyu Fang, Georg P Berg, Manoel Couder, Alexander C Dombos, Joseph Henning, Jerry D Hinnefeld, Patricia L Huestis, Luis A Morales, Shane Moylan, Fabio Rivero, Daniel Robertson, Christopher J Seymour, Gwenaelle Seymour, Michael A Skulski, Edward J Stech, Michael C F Wiescher The St. George recoil mass separator at the University of Notre Dame was designed to study radiative capture reactions relevant for stellar burning. St. George is coupled to the 5U accelerator at the Nuclear Science Laboratory. A benchmark reaction, 20Ne(α, γ) 24Mg, was studied in November 2019. While showing results consistent with literature, 5U accelerator beam contaminants, which have indistinguishable mass and momentum from recoils, have limited the ability to extend the measurements to lower energies. A Wien filter was installed on the 5U transport line earlier this year with the goal of rejecting the beam contaminants before they enter St. George. The significant background reduction measured in a recent experimental test will be presented. |
Thursday, October 14, 2021 9:42AM - 9:54AM |
PD.00002: Constraining the electron-capture rates of neutron rich nuclei with (d,2He) reaction in inverse kinematics. Simon Giraud, Juan C Zamora, Miles DeNudt, Remco G Zegers, Daniel Bazin, Yassid Ayyad, Saul Beceiro-Novo, Jie Chen, Marco Cortesi, Cavan Maher, Wolfgang Mittig, Felix Ndayisabye, Shumpei Noji, Jorge Pereira, Zarif Rahman, Jaclyn M Schmitt, Michael Serikow, Jason Surbrook, Lijie Sun, Nathan Watwood, Tyler Wheeler Nuclear charge-exchange reactions can be used to estimate the electron-capture rates which are key quantities in a variety of astrophysical scenarios. Over the past decades, great progress has been made to constrain electron-capture rates on stable nuclei by using reactions in forward kinematics. However, the unstable neutron-rich nuclei capturing the most during, for example, the core-collapse supernovae, remained inaccessible. Recently a (d,2He) charge-exchange reaction in inverse kinematics with the Active-Target Time-Projection Chamber and the S800 Spectrograph was developed at NSCL, for extracting Gamow-Teller strengths in the β+ direction on unstable nuclei. This makes it possible, for the first time, to constrain electron-capture rates on neutron-rich nuclei. In this talk I will discuss recent results of the pilot 14O(d,2He) experiment. |
Thursday, October 14, 2021 9:54AM - 10:06AM |
PD.00003: Detection and parameter estimation of gravitational waves from compact binary mergers using Deep Learning Plamen G Krastev, Kiranjyot Gill, V. Ashley Villar, Edo Berger One of the key challenges of real-time detection and parameter estimation of gravitational waves (GWs) from compact binary mergers is the computational cost of conventional matched-filtering and Bayesian inference approaches. In particular, the application of these methods to the full signal parameter space available to the gravitational-wave detectors, and/or real-time parameter estimation is computationally prohibitive. On the other hand, rapid detection and inference are critical for prompt follow-up of the electromagnetic and astro-particle counterparts accompanying important transients, such as binary neutron-star (BNS) and black-hole neutron-star (BHNS) mergers. Training deep neural networks to identify specific signals and learn a computationally efficient representation of the mapping between GW signals and their parameters allows both detection and inference to be done quickly and reliably, with high sensitivity and accuracy. We present our results of detection and characterization of GWs from compact binary mergers in real LIGO data, with a particular attention to systems involving neutron stars. The implications for detection and interpretation of recent and future GW signals from BNS and BHNS mergers, and the equation of state (EOS) of dense matter will be discussed. |
Thursday, October 14, 2021 10:06AM - 10:18AM |
PD.00004: Dependence of (n, γ) - (γ, n) Equilibrium r-Process Abundances on Nuclear Physics Properties Mengke Li In most r-process expansions, the dominant nuclear evolution occurs in an (n,γ)-(γ,n) equilibrium in which nuclei rapidly exchange neutrons but change charge much more slowly by beta decay. Freezeout from this equilibrium shapes the final abundances but does not significantly alter the overall global abundance pattern; therefore, it is important to understand the details of (n,γ)-(γ,n) equilibrium both because it is the main evolution phase that determines the final abundance pattern and because it is the starting point for the freeze out. Through use of a simple, but realistic phenomenological nuclear physics model, we show that isotopic abundances versus neutron number in (n,γ)-(γ,n) equilibrium are well approximated as gaussians. Nuclear pairing causes isotopic abundances to alternate between two gaussians, and shell effects cause the isotopic abundances to shift from one gaussian to another when the neutron number crosses a magic number. Nuclear physicists can use insights from our model to understand how their detailed theoretical or experimental nuclear data affect r-process nucleosynthesis during the (n,γ)-(γ,n) equilibrium phase. We have also prepared a number of Jupyter notebooks that allow the user to study (n,γ)-(γ,n) equilibrium isotopic abundances with either our simple nuclear physics model or more realistic ones(https://github.com/mengkel/ng-gn-abundances). |
Thursday, October 14, 2021 10:18AM - 10:30AM |
PD.00005: Implications of PREX-2 on the Nuclear Equation of State Brendan T Reed, Farrukh J Fattoyev, Charles J Horowitz, Jorge Piekarewicz The heavy neutron-rich nucleus of Pb-208 has a large neutron-rich skin. Recently, the PREX collaboration announced a very precise measurement of this skin using parity violating electron scattering. This measurement constrains the properties of neutron rich matter and the equation of state of dense matter. In this talk, I compare the measurement of the neutron skin to the properties of neutron stars. This includes a comparison of the LIGO/VIRGO observations of a binary neutron star merger and to the NICER X-ray telescope's observations of the radius of a neutron star |
Thursday, October 14, 2021 10:30AM - 10:42AM |
PD.00006: Webnucleo.org Jaad Tannous, Bradley S Meyer Webnucleo is a Clemson University based project focused on nuclear astrophysics, nucleosynthesis, stellar evolution, astronomy, and cosmochemistry. The Webnucleo team is producing a number of products that researchers, educators, and students may find useful in studying topics of interest to the Webnucleo group. These products include open-source codes, Docker images, and Jupyter notebooks. The website webnucleo.org, also https://webnucleo.readthedocs.io, serves as a central resource for exploring those products. We present Webnucleo.org, its philosophy, features and some products relevant for nuclear physics and astrophysics. |
Thursday, October 14, 2021 10:42AM - 10:54AM |
PD.00007: Preparation of the SECAR system for the first (p,n) reaction measurement. Pelagia Tsintari, Adriana Banu, Georg P Berg, Manoel Couder, Nikolaos Dimitrakopoulos, Alfredo Estrade, Ruchi Garg, Rahul Jain, Caleb A Marshall, Zachary P Meisel, Fernando Montes, Georgios Perdikakis, Hendrik Schatz, Louis Wagner Neutron-induced reactions are essential to the nucleosynthesis of the elements heavier than iron. Recent studies show that key (n,p) reactions, such as the 56Ni(n,p)56Co and 64Ge(n,p)64Ga, regulate the efficiency of the so-called neutrino-p process (νp-process), which is responsible for the formation of elements between nickel (Ni) and tin (Sn) in type II supernovae. Nucleosynthesis in νp-process occurs at slightly proton-rich regions in the neutrino-driven wind of core-collapse supernovae, via a sequence of proton-capture reactions and (n,p) reactions. The small abundance of neutrons needed originates from anti-neutrino captures on free protons. |
Thursday, October 14, 2021 10:54AM - 11:06AM |
PD.00008: Radiative strength of neutron-rich strontium isotopes Adriana Sweet, Darren L Bleuel, Nicholas D Scielzo, Lee A Bernstein, Jason A Clark, Katherine L Childers, Alexander C Dombos, Frank L. B. Garrote, Bethany L Goldblum, Andreas Gorgen, Magne Guttormsen, Caley Harris, Ann-Cecilie Larsen, Rebecca Lewis, Sean N Liddick, Stephanie Lyons, Farheen Naqvi, Alicia Palmisano, Andrea L Richard, Debra Richman, Daniel Santiago-Gonzalez, Guy Savard, Sunniva Siem, Mallory K Smith, Artemis Spyrou, Jasmina Vujic, Mathis Wiedeking Our understanding of neutron-induced reactions on nuclei far from stability has far reaching implications for cosmogenic nucleosynthesis and fundamental nuclear physics. Direct measurement of the radiative-capture cross section is experimentally inaccessible for these short-lived nuclei; however, indirect methods such as the β-Oslo Method enable the experimental constraint of key nuclear properties that are inputs for reaction-theory calculations. |
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