Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session FE: Mini-Symposium: Beta Decay: Nuclear Astrophysics, Structure, and Applications II |
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Chair: Scott Marley, Louisiana State University |
Friday, October 30, 2020 2:00PM - 2:12PM |
FE.00001: Electroweak transitions in nuclei from first principles Grigor Sargsyan, Kristina Launey, Tomas Dytrych, Jerry Draayer We present beta decay rates and recoil matrix elements calculated using the \textit{ab initio} symmetry-adapted no-core shell model (SA-NCSM). The SA-NCSM utilizes emergent symmetries in nuclei in order to reduce the dimensionality of the model space. This, in turn, allows one to reproduce the low-energy nuclear dynamics with only a small fraction of the model space, and hence making solutions to heavier nuclei feasible. The symmetry-adapted basis of the SA-NCSM is well suited for describing electromagnetic and beta-decay transitions enabling us to use the full capability of the model and perform calculations for up to pf-shell nuclei. This work discusses calculations of beta recoil matrix elements from first principles that help to probe fundamental interactions. It also focuses on a study of the $g_A$ quenching problem for bare interactions (no renormalization involved) and with collective correlations that are well described within the model, as well as on a study of $^{48}$Ca and $^{48}$Ti of interest to neutrinoless double beta decays. [Preview Abstract] |
Friday, October 30, 2020 2:12PM - 2:24PM |
FE.00002: Precise measurement of $^{28}$Al half-life Biying Liu, Maxime Brodeur, Daniel Bardayan, Frederick Becchetti, Chevelle Boomershine, Daniel Burdette, Louis Caves, Orlando Gomez, Samuel Henderson, James Kolata, Jacob Long, Austin Nelson, Patrick O'Malley, Andres Pardo Precise and accurate half-lives of beta-decaying nuclei are important for a myriad of applications including the determination of nucleosynthesis pathways, and fundamental tests the weak interaction. Unfortunately, the half-life of several isotopes currently stem from conflicting measurements, which affects their accuracy and precision. The half-life of $^{28}$Al is one such, as it includes several precise, but discrepant measurements resulting in the application of a 0.1$\%$ uncertainty on the world value by the NNDC. In an effort to remedy to the situation, a precise half-life measurement of $^{28}$Al was performed using the $\beta$ counting station at the University of Notre Dame's Nuclear Science Laboratory. The new measurement falls in between the two most recent values while disagreeing with both, prompting the need for another independent measurement. The experiment, data analysis and a new world value will be presented. [Preview Abstract] |
Friday, October 30, 2020 2:24PM - 2:36PM |
FE.00003: Precision Half-life Measurement of 33Cl Patrick O'Malley, Maxime Brodeur The understanding of fundamental symmetries has really been expanded in the past decade thanks to new precision measurements. In particular, the techniques used to extract the V$_{ud}$ matrix element from superallowed pure Fermi transitions could be tested using precise determinations of $ft$ values for superallowed mixed transitions between mirror nuclides. The calculations of $ft$ values require the half-life, branching ratio, and Q-value. The accepted $^{33}$Cl decay half-life arises from a series of old measurements. In this work, the life-time was determined counting $\beta$ particles from the decay of the implanted $^{33}$Cl. The $^{33}$Cl beam was produced via the $^{32}$S($d,n$) transfer reaction and separated by the TwinSol facility of the Nuclear Science Laboratory of the University of Notre Dame. The $^{33}$Cl data will be presented and the analysis will be discussed. [Preview Abstract] |
Friday, October 30, 2020 2:36PM - 2:48PM |
FE.00004: The Latest Total Absorption Results from MTAS Bertis Rasco Measuring accurate total $\beta$-feeding patterns is important for understanding reactor decay heat, reactor antineutrino production, and to the freeze out component of the r process in relation to the relative abundances of elements in the galaxy. Total $\beta$-feeding patterns include all decay branches, including ground-state to ground-state decay, feeding to excited states, and $\beta$-delayed neutron branches. Over the last decade measuring $\beta$-feeding patterns using total absorption spectroscopy has become an important complement to high precision $\gamma$ measurements. Total absorption spectroscopy involves detectors with extremely high efficiency which minimizes beam-time use and overcomes the pandemonium effect in order to extract total $\beta$-feeding patterns for nuclei abundantly produced in nuclear fission. It also allow extraction of the ground-state to ground-state feeding and $\beta$-delayed neutron branches. The Modular Total Absorption Spectrometer (MTAS) is the worlds largest total absorption spectrometer that is capable of extracting total $\beta$-feeding patterns. We will present new results of several nuclei that were measured at the HRIBF at Oak Ridge National Laboratory and at Argonne National Laboratory. [Preview Abstract] |
Friday, October 30, 2020 2:48PM - 3:00PM |
FE.00005: $\beta$-Decay Studies of Mass 104 Isotopes Using MTAS Alexander Laminack, Bertis Rasco, Krzysztof Rykaczewski, Shuai Peng Approximately 8\% of the heat produced in a nuclear reactor comes from decay chains of fission products. $\gamma$ radiation emitted in these decays is commonly referred to as “decay heat.” In order to model decay heat, accurate knowledge of $\beta$-feeding intensities and following gamma radiation is needed. This includes ground-state feeding, excited-state feeding, as well as $\beta$-delayed neutron emission. Previous high-precision measurements suffer from low detection efficiency and are thus susceptible to the so called pandemonium effect resulting in inaccurate decay patterns. The Modular Total Absorption Spectrometer (MTAS) achieves a high detection efficiency for $\gamma$ rays by utilizing one ton of NaI scintillators. In addition to being sensitive to $\gamma$ rays associated with the pandemonium effect, total absorption spectroscopy with MTAS allows for the measurement of ground-state to ground-state feeding intensities and $\beta$-delayed neutron emission branching ratios. $\beta$-feeding intensities of $^{104}$Nb, $^{104}$Mo, and $^{104}$Tc were measured with MTAS at Argonne National Laboratory's CARIBU facility. The results of these measurements as well as a comparison to previous measurements will be presented here. [Preview Abstract] |
Friday, October 30, 2020 3:00PM - 3:12PM |
FE.00006: Beta Spectrum Module: A Detector for Directly Measuring Beta Shape Factors T. Ruland, J.C. Blackmon, M.T. Febbraro, B.C. Rasco, K.P. Rykaczewski Previous measurements of beta decay have generally depended upon gamma detection with modest efficiency. This has resulted in a bias in estimates of the energy released towards betas and antineutrinos at the expense of gamma rays, with implications for reactor decay heat. The measured spectrum of antineutrinos at higher energies also disagrees with the predicted flux. We have developed a Beta Spectrum Module (BSM) for direct measurement of the beta shape factors to alleviate these anomalies in the reactor antineutrino spectrum. [Preview Abstract] |
Friday, October 30, 2020 3:12PM - 3:24PM |
FE.00007: $\beta -$decay strength distributions of neutron-rich cobalt isotopes for r-process nucleosynthesis S. Lyons, A. Spyrou, S.N. Liddick, R.L. Lewis, B.A. Brown, K.L. Childers, C. Harris, A. Palmisano, D. Richman, R.T Zegers, M.K. Smith, M. Guttormsen, A.C. Larsen, M.R. Mumpower, D.L. Bleuel, N.D. Scielzo, B.P. Crider, A. Sweet, J. Engel, E.M. Ney, A.C. Dombos, A. Simon The r process is known to produce roughly half of the isotopes of heavy elements. Sensitivity studies have shown that the final abundance distributions of r-process nuclei are greatly impacted by uncertainties in $\beta $-decay properties, such as half-lives. In order to improve these uncertainties, the technique of total absorption spectroscopy is employed to improve $\beta $-decay strength distributions. The decay of several neutron-rich cobalt isotopes were measured using the technique of total absorption spectroscopy at the NSCL. The high Q-value of these isotopes allows for the study of $\beta $-decay properties over a broad energy range and the resultant $\beta $-decay intensities and deduced Gamow-Teller strengths are compared to theoretical models that are commonly used in r-process network calculations. Impacts of the current findings will be discussed. [Preview Abstract] |
Friday, October 30, 2020 3:24PM - 3:36PM |
FE.00008: Experimental study on the $\beta$- strength function in the decay of neutron-rich $^{133}$In Zhengyu Xu, Miguel Madurga, Robert Grzywacz, Thomas King, Corey Halverson, Joseph Heideman, Maninder Singh, Rin Yokoyama An experimental work has been recently conducted at the ISOLDE decay station (IDS), to study the neutron-unbound states in $^{133}$Sn following the beta decays of $^{133}$In. The main decay strength of $Z<50$ and $N>82$ nuclei is anticipated to be the Gamow-Teller transition transforming a deeply bound $g_{7/2}$ neutron into a $g_{9/2}$ proton. In addition, first-forbidden transitions are postulated to take noticeable strength feeding lower-lying states. In order to examine these highly excited states above neutron separation energy, the neutron time-of-flight array, VANDLE, was installed at IDS to measure $\beta$-delayed neutron-emission energies. In this contribution, we will discuss our latest results regarding the excitation energies, branching ratios, and log-ft of a series of neutron unbound states observed in the $^{133}$In decay. To gain insights into the microscopic configurations of those states and the strength distribution in $^{133}$Sn, we carried out a large-scale shell-model calculation, of which the result and its comparison with experimental data will also be presented. [Preview Abstract] |
Friday, October 30, 2020 3:36PM - 3:48PM |
FE.00009: Precision $\beta $-decay branching ratio measurements for long-lived fission products. Miguel Bencomo, Karolina Kolos, Nicholas D Scielzo, Wei Jia Ong, Mark A Stoyer, Anton P Tonchev, Mary T Burkey, Dan Melconian, Victor E Iacob, John C Hardy, Jason A Clark, Matthew Gott, Daniel Santiago-Gonzalez, Guy Savard, Adrian Valverde, Xinliang Yan, Brian Champine, Tyler Nagel, Eric B Norman, Amber M Hennessy, Rodney Orford, Dwaipayan Ray, Louis Varriano, Graeme Morgan, Shaofei Zhu Nuclear data for fission products are used to determine fission-product yields, which impact nuclear applications. Many branching ratio measurements of long-lived fission products (t$_{\mathrm{1/2~}}$\textgreater 1d) suffer from high uncertainties, which contribute to the uncertainties in the determined fission yields. We developed a new experimental method to precisely (\textasciitilde 1{\%} precision) measure the~$\gamma $-ray branching ratios in the~$\beta $~decay of long-lived fission products. The approach involves production of a pure fission-product sample at the CARIBU facility at ANL on an ultra-thin carbon foil and a subsequent decay measurement with a 4$\pi $~gas proportional counter and a meticulously-calibrated high-purity germanium (HPGe) detector at TAMU. We will present results for~$^{\mathrm{95}}$Zr/$^{\mathrm{95}}$Nb,~$^{\mathrm{147}}$Nd, and$^{\mathrm{156}}$Eu. [Preview Abstract] |
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