Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session H11: Nuclear Astrophysics II.Live
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Sponsoring Units: DNP Chair: Robert Janssens, UNC |
Sunday, April 18, 2021 10:45AM - 10:57AM Live |
H11.00001: Sensitivity study to identify impactful reactions in X-ray burst nucleosynthesis using MESA. Amber Lauer-Coles, Ian Lapinski, Brittney Contreras, Arthur Champagne This work will discuss a sensitivity study based on a model of a low mass X-ray binary using Modules for Experiments with Stellar Astrophysics. Type I x-ray bursts are a thermonuclear explosion that occur in hydrogen and helium rich material on the surface of an accreting neutron star. Thermonuclear runaway proceeds up to the A=100 region via the (\textit{a,p}) and (\textit{r-p}) processes. Understanding these reactions is key to understanding the explosion mechanism, but many involve unstable nuclei that are difficult to produce for use in experiments. Thus, sensitivity studies are a useful steering mechanism to guide the experimental community and optimize the application of resources. The stellar model includes a nuclear reaction network of 305 species and all the reactions that connect them. This model is run many times in which a single reaction is varied by a factor to test its effect on important features of the model, such as observables and abundances. From this the most impactful reactions are selected. This talk will discuss the results of the first round, or coarse-resolution study and preliminary results of the second round, where finer-resolution variations of key reaction rates are being implemented. [Preview Abstract] |
Sunday, April 18, 2021 10:57AM - 11:09AM Live |
H11.00002: $^{30}$P$(p,\gamma)^{31}$S reaction rate in novae: lifetimes of $^{31}$S states L.J. Sun, C. Fry, M. Alcorta, S.S. Bhattacharjee, T. Budner, R. Caballero-Folch, B. Davids, N. Esker, L. Evitts, M. Friedman, A.B. Garnsworthy, B. Glassman, G. Hackman, J. Henderson, O. Kirsebom, A. Kurkjian, P. Machule, C. Pearson, D. Perez-Loureiro, C. Ruiz, P. Ruotsalainen, J. Smallcombe, J. Surbrook, W. Williams, C. Wrede In classical novae, the $^{30}$P$(p,\gamma)^{31}$S reaction acts as a nucleosynthesis bottleneck. Its reaction rate is dominated by proton capture into narrow $^{31}$S resonances. To constrain the resonance strengths, we carried out lifetime measurements of the $^{31}$S resonances using the Doppler Shift Lifetime device at the TRIUMF-ISAC facility. The $^{31}$S excited states were populated by the $^{3}$He$(^{32}$S$,\alpha)^{31}$S reaction. The deexcitation $\gamma$ rays were detected by HPGe detectors in coincidence with the $\alpha$ particles detected by a Si telescope. The lifetimes for $^{31}$S excited states including a resonance in the region of interest were constrained by using the Doppler Shift Attenuation Method. [Preview Abstract] |
Sunday, April 18, 2021 11:09AM - 11:21AM Live |
H11.00003: Experimentally constraining the $^{\mathrm{30}}$P(p,$\gamma )^{\mathrm{31}}$S reaction rate and its effect on nova nucleosynthesis Tamas Budner, Moshe Friedman, Chris Wrede, Alex Brown, Jordi José, David Pérez-Loureiro, Yassid Ayyad, Dan Bardayan, Kyungyuk Chae, Alan Chen, Kelly Chipps, Marco Cortesi, Brent Glassman, Matthew Hall, Molly Janasik, Johnson Liang, Patrick O'Malley, Emmanuel Pollacco, Athanasios Psaltis, Jordan Stomps, Lijie Sun, Jason Surbrook, Tyler Wheeler Constraining the $^{\mathrm{30}}$P(p,$\gamma )^{\mathrm{31}}$S reaction is crucial for understanding ONe nova nucleosynthesis. Its rate influences the isotopic and chemical abundances of nova ejecta, particularly in the Si-Ca mass region, which may help identify presolar grains of putative nova origin. The reaction proceeds primarily through proton capture into narrow, isolated resonances at low energies. By determining the strengths of a few key resonances, we can substantially reduce reaction rate uncertainties. We report the results of a $^{\mathrm{31}}$Cl $\beta $-decay experiment in which we measured the very weak proton emission branch of a low-energy resonance using the GADGET. We calculated the total thermonuclear rate and determined this to be the dominant resonance in the reaction. We use hydrodynamic simulations to study this rate's effect on nuclear yields in classical nova ejecta. [Preview Abstract] |
Sunday, April 18, 2021 11:21AM - 11:33AM Live |
H11.00004: Spin and parities of sub-threshold resonances and their interference effects in the $^{18}$F destruction reaction $^{18}$F(p,$\alpha$)$^{15}$O Federico Portillo Chaves, Kiana Setoodehnia, Caleb Marshall, Richard Longland The $^{18}$F(p,$\alpha$)$^{15}$O reaction dominates $^{18}$F destruction in classical nova explosions. However, uncertainties in its cross section at low energy place a poor constraint on the $^{18}$F abundances predicted by nova models. The incomplete knowledge of the interference effects between broad resonances (e.g. at E$_{CM}$ = 665 keV) and those near the proton-threshold constitutes an important source for these uncertainties. Accurately determining resonance parameters such as energies, spin and parities (J$^{\pi}$), and widths of sub-threshold and unbound states is crucial to study these interference effects. In this talk we will present the results of a $^{20}$Ne($^{3}$He,$\alpha$)$^{19}$Ne neutron pickup reaction performed at the Triangle Universities Nuclear Laboratory using its Enge split-pole magnetic spectrograph. In particular, we will show results of the analysis done to determine the J$^{\pi}$ of the 6.290 MeV state (E$_{CM}$ -120 keV resonance). Also, we will present the results for the 6.132 MeV state (E$_{CM}$= -278 keV) together with other states of astrophysical interest, and highlight their effect on the $^{18}$F(p,$\alpha$)$^{15}$O reaction rate at nova temperatures. [Preview Abstract] |
Sunday, April 18, 2021 11:33AM - 11:45AM Live |
H11.00005: Measurements of (alpha,n) cross-sections relevant for the r-process Nabin Rijal, S. Ahn, F. Montes, Z. Meisel, H. Schatz The fast-expanding neutron-rich neutrino-driven winds in the core-collapse supernovae are favorable scenarios for the nucleosynthesis of the light-heavy elements. Charge particle reactions, especially ($\alpha$,n) create seeds for the weak r-process populating abundances of near stable isotopes for the Sr-Ag range, for which there remains a large discrepancy between observed and predicted elemental abundances in the metal-poor halo stars. These abundances are significantly sensitive to the ($\alpha$,n) reaction rates. Only very few of these reactions had been measured in the energy range relevant for weak r-process astrophysical conditions. Theoretical calculations of reaction rates for such scenarios are very uncertain and model-dependent. In this talk, I will discuss measurements of $^{85}$Br,$^{75}$Ga, and $^{85}$Rb ($\alpha$,n) cross-sections using the HabaNERO detector at ReA3, NSCL along with future possibilities to measure and constrain other important ($\alpha$,n) reactions relevant for the r-process. [Preview Abstract] |
Sunday, April 18, 2021 11:45AM - 11:57AM Live |
H11.00006: The Design, Validation, and Future Plans for a New Neutron Detector at Ohio University Kristyn Brandenburg, Zachary Meisel, Carl Brune, Doug Soltesz, Shiv Subedi Though ($\alpha$,n) reaction cross sections play a key role in nuclear astrophysics and applications, many are poorly constrained by nuclear experiments and have significant uncertainties in theoretical predictions. Improving this situation will be done in part using a newly developed neutron long counter, HeBGB, at the Ohio University Edwards Accelerator Lab. The detector was designed using the MCNP6 software to have near constant efficiency in the neutron energy range relevant for core-collapse supernovae and special nuclear materials. Efficiency validation measurements have been performed with HeBGB, which utilize well-characterized reactions with constrained cross sections and known neutron energies. The first measurement conducted with HeBGB is $^{27}{\rm Al}$($\alpha$,n) near threshold, which dominates the astrophysical rate, has disagreement between theoretical predictions and has only one prior measurement in this energy regime. [Preview Abstract] |
Sunday, April 18, 2021 11:57AM - 12:09PM Live |
H11.00007: TPC Detectors for Studies in Nuclear Astrophysics I: The Detector Deran K Schweitzer, Moshe Gai, Sarah R Stern, Robin Smith, Wojciech Dominik, Mikolaj Cwiok, Zenon Janas, Chiara Mazzocchi Carbon and oxygen are formed during stellar helium burning; however, the carbon-to-oxygen ratio is still not well determined, due to the ill-understood $^{\mathrm{12}}$C($\alpha $,$\gamma )^{\mathrm{16}}$O reaction. In this work, we present a new approach for measuring the $^{\mathrm{12}}$C($\alpha $,$\gamma )^{\mathrm{16}}$O reaction, by measuring the inverse $^{\mathrm{16}}$O($\gamma $, $\alpha )^{\mathrm{12}}$C reaction using a quasi-monoenergetic gamma beam from the HI$\gamma $S facility, and a time-projection chamber (TPC) detector operating with CO$_{\mathrm{2}}$ gas. In the optical readout TPC (O-TPC), anode (total energy) and PMT (time projection) signals, together with CCD camera images of the tracks, were measured. Extensive Monte Carlo simulations of the O-TPC detector and the Warsaw electronic readout TPC (eTPC), which will be used at the HIGS facility [M. Gai \textit{et al}, NIMA \textbf{954}, 161779 (2020)], were performed. We discuss the Monte Carlo simulation of the UConn-TUNL O-TPC and the electric field simulation of the Warsaw eTPC. Simulations of the electric field using ANSYS EDT (MAXWELL) of the Warsaw eTPC, along with Monte Carlo simulations of the efficiency of the UConn-TUNL O-TPC, were performed, and will be presented. [Preview Abstract] |
Sunday, April 18, 2021 12:09PM - 12:21PM Live |
H11.00008: TPC Detector for Studies in Nuclear Astrophysics, II: The HI$\gamma S Measurement Sarah R. Stern, Deran K. Schweitzer, Moshe Gai, Robin Smith, Mohammad W. Ahmed The UConn-TUNL Optical Readout Time Projection Chamber (O-TPC) detector operating with CO$_{\mathrm{2}}$ gas, discussed in the previous abstract was used to study the $^{\mathrm{16}}$O($\gamma $,$\alpha )^{\mathrm{12}}$C reaction, the time reverse of the $^{\mathrm{12}}$C($\alpha $,$\gamma )^{\mathrm{16}}$O reaction that occurs during stellar helium burning. The cross-section of this reaction was measured at nominal gamma beam energies of: 9.08 MeV, 9.38 MeV, 9.58 MeV, 9.78 MeV, 10.1 MeV, and 10.4 MeV. The actual beam energies were measured using attenuated gamma beam implanted into the HPGe detector and the effective beam energies were calculated. Anode (total energy) and PMT (time projection) signals, together with CCD camera images of the tracks were measured. The line shape of the measured signals were used to distinguish between $^{\mathrm{12}}$C and $^{\mathrm{16}}$O dissociation events. For each event the total energy and the scattering angle of the track were measured and complete angular distributions were measured at 0\textdegree -180\textdegree . The angular distributions were analyzed using partial wave decomposition with the three fit parameter: E1, E2 and the E1-E2 mixing phase angle ($\varphi _{\mathrm{12}})$. For the first time, the extracted $\varphi _{\mathrm{12}}$ fit values agree with the prediction based on unitary: $\varphi_{\mathrm{12}}=\delta_{\mathrm{2}}$-$\delta _{\mathrm{1}}$-atan($\eta $/2). [Preview Abstract] |
Sunday, April 18, 2021 12:21PM - 12:33PM Live |
H11.00009: Testing Hadronic Interactions Beyond Collider Energies With the Pierre Auger Observatory Jorge Fernández Soriano The muon content of extensive air showers is an observable sensitive to the primary composition and to the hadronic interaction models. I will discuss different methods which allow us to estimate the muon number at ground level and the muon production depth by exploiting the measurement of the longitudinal, lateral, and temporal distribution of particles in air showers recorded at the Pierre Auger Observatory. The results, obtained for primaries with energy $\sim10^{10}\,$GeV (or about $140\,$TeV center-of-mass energy for proton primaries), show a significant discrepancy in the shower muon content (greater than $2\sigma$, statistical and systematics combined in quadrature) between predictions of LHC-tuned hadronic event generators and Auger data. This intriguing observation convincingly demonstrates that it is possible to test particle physics well above $100\,$TeV in the UHECR-air nucleon center-of-mass energy, using hybrid UHECR air showers, even with a mixed primary composition. I will also discuss how the added muon-electromagnetic separation and the significantly higher data-taking rate for the highest energy hybrid events provided by AugerPrime, the upgrade of the Pierre Auger Observatory, will give new insights on hadronic interactions well beyond collider energies. [Preview Abstract] |
Sunday, April 18, 2021 12:33PM - 12:45PM Live |
H11.00010: Measurement of the 114Cd(n,g) cross section using the Detector for Advanced NeutronCapture Experiments at LANL K.T. Assumin-Gyimah, B.P. Crider, D. Dutta, T.H. Ogunbeku, D.P. Siwakoti, A. Couture, C. Fry, C.J. Prokop, J.L. Ullmann, S. Lyons The \textsuperscript{114}Cd nucleus can impact nondestructive assay techniques that utilize Cd for neutron absorption as well as nuclear astrophysics applications in the study of the s-process. A recent sensitivity study of s-process abundances found that the uncertainties of the cross section for neutron capture on \textsuperscript{114}Cd have a significant impact on final abundance uncertainties. Therefore, precise knowledge of the \textsuperscript{114}Cd(n,g)\textsuperscript{115}Cd cross section is critical across a large range of incident neutron energies. Additionally, information on \textsuperscript{115}Cd Photon Strength Function (PSF) is essential for improving the reliability of calculations investigating the nature of possible M1 strength in \textsuperscript{114}Cd and properties of nuclei far from stability. We will present preliminary results from the measurement of neutron capture cross section of \textsuperscript{114}Cd for incident neutron energies from 1 keV to 300 keV performed with the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos Neutron Science Center. [Preview Abstract] |
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