Bulletin of the American Physical Society
2019 Fall Meeting of the APS Division of Nuclear Physics
Volume 64, Number 12
Monday–Thursday, October 14–17, 2019; Crystal City, Virginia
Session SA: Particles, Nuclei and Stars via Beta Decay |
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Chair: Kelly Chipps, Oak Ridge National Laboratory Room: Salon 1 |
Thursday, October 17, 2019 10:30AM - 11:06AM |
SA.00001: Polarized angular correlations in $^{37}$K: Recent results from TRINAT Invited Speaker: Dan Melconian Nuclear $\beta$ decay has a long-standing history of shaping and testing the standard model of particle physics, and it continues to this day with elegant, ultra-precise low-energy nuclear experiments. Measurements of the (un)polarized angular correlations between the electron, neutrino and recoil momenta following nuclear $\beta$ decay can be used to search for exotic currents contributing to the dominant $(V-A)$ structure of the weak interaction. Precision measurements of the correlation parameters to $<0.1\%$ would be sensitive to (or meaningfully constrain) new physics, complementing other searches at large-scale facilities such as the LHC. This talk will discuss recent work from the TRIUMF Neutral Atom Trap (TRINAT) collaboration. We utilize neutral atom trapping techniques with optical pumping methods to highly-polarize ($>99\%$) a very cold and localized ($<1~\mathrm{mK}$ and $<1~\mathrm{mm}^3$) source of short-lived ($\sim1~\mathrm{s}$) $^{37}$K atoms. Recently, we measured the $\beta$ asymmetry parameter, $A_\beta$, of this decay to 0.3\%, the best relative accuracy of any $\beta$-asymmetry measurement in a nucleus or the neutron. These methods and recent results will be presented along with future prospects for improving the precision to $<0.1\%$. [Preview Abstract] |
Thursday, October 17, 2019 11:06AM - 11:42AM |
SA.00002: Beta-Delayed Neutron Measurements for R-Process Isotopes with BRIKEN Invited Speaker: Alfredo Estrade Most of the unstable isotopes produced during the rapid neutron capture process (r-process) are expected to be $\beta$-delayed neutron emitters; a decay mode that populates neutron-unbound states in the daughter nuclei. The probability for $\beta$-delayed neutron emission is a key input for models of r-process nucleosynthesis in neutron star mergers and other astrophysical sites. $\beta$-delayed neutrons contribute to the density of free neutrons in the astrophysical environment, in particular during the late stages of the neutron capture phase of the r-process, and this decay mode also affects the final abundance of the elements produced once unstable isotopes have decayed to $\beta$-stability. A significant number of nuclei along the path of the r-process are finally within reach of decay experiments, thanks to a new generation of laboratories designed to produce intense beam of neutron-rich isotopes coupled with sensitive experimental setups. Beta-delayed neutrons at RIKEN (BRIKEN) is a setup for $\beta$-decay measurements at the Radioactive Isotope Beam Factory (RIBF) in RIKEN, Japan, which achieves a high detection efficiency with a state-of-the-art neutron detector based on $^{3}$He proportional counters. Since the first BRIKEN experiment, in 2017, our collaboration has studied $\beta$-delayed neutron emission in regions of the nuclear chart extending from cobalt (Z=27) to gadolinium (Z=64). The experiments covered regions that affect salient features of the r-process: the A=130 and the rare-earth elements abundance peaks. I will present the program of experiments of the BRIKEN collaboration, and discuss some of the first results and their impact in r-process models. [Preview Abstract] |
Thursday, October 17, 2019 11:42AM - 12:18PM |
SA.00003: Gamma-ray Spectroscopy Experiments with Rare-Isotope Beams and Highly-Efficient Arrays at TRIUMF-ISAC Invited Speaker: Corina Andreoiu Located at the TRIUMF laboratory in Vancouver, Canada, the Isotope Separator and ACcelerator -- ISAC -- facility is one of the world's most advanced isotope separator on-line facilities providing high-intensity and high-purity radioactive ion beams for a wide variety of science programmes. ISAC's $\gamma $-ray spectroscopy programme for studying nuclear structure, nuclear astrophysics and tests of fundamental symmetries is centred around two major research instruments: (i) the GRIFFIN $\gamma $-ray spectrometer for $\beta $- and $\beta $-delayed $\gamma $-ray spectroscopy experiments with the low-energy beams provided by ISAC-I, and (ii) the TIGRESS $\gamma $-ray spectrometer for in-beam experiments with the accelerated radioactive-ion beams provided by ISAC-II. Both TIGRESS and GRIFFIN consist of 16 Compton-suppressed HPGe clovers and are augmented with powerful suites of ancillary detectors for coincidence measurements and channel selection leading to comprehensive spectroscopy studies of exotic nuclei. An overview of these facilities and recent results from the nuclear structure studies they enable are presented. The infrastructures of TIGRESS and GRIFFIN have been funded through contributions from the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, TRIUMF, University of Guelph, British Columbia Knowledge Development Fund and the Ontario Ministry of Research and Innovation. TRIUMF receives funding through a contribution agreement through the National Research Council Canada. This work is supported by the Natural Sciences and Engineering Research Council of Canada. Replace this text with your abstract. [Preview Abstract] |
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