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 LF: Mini-Symposium: Precision Beta Decay II |
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Chair: Leendert Hayen, NCSU |
Saturday, October 31, 2020 10:30AM - 10:42AM |
LF.00001: The St. Benedict Ion Trapping System at the Nuclear Science Laboratory D.P. Burdette, M. Brodeur, J.A. Clark, J. Long, P.D. O'Malley, A. Pardo, R. Ringle, G. Savard, A.A. Valverde St. Benedict, the Superallowed Transition Beta-Neutrino Decay-Ion-Coincidence Trap, is under construction at the University of Notre Dame's Nuclear Science Laboratory. This ion trapping system is composed of three main components; a large-volume gas cell, a radio frequency quadrupole (RFQ), and a Paul trap. In tandem, the gas cell and RFQ will prepare radioactive beams produced by the TwinSol facility for injection into the Paul trap. While trapped, the radioactive species of interest will be allowed to decay, and coincidence measurements of recoiling nuclei and beta particles will allow for reconstruction of the beta spectrum, and consequently, the extraction of the $\beta$-$\nu$ angular correlation coefficient, $a_{\beta\nu}$. This will allow for the determination of the Fermi to Gamow-Teller mixing ratio, $\rho$, for members of the ensemble of T=1/2 superallowed $\beta$ decays whom have not had this quantity measured experimentally. The determination of $\rho$ for these decays will allow for the calculation of a precise $\text{V}_{\text{ud}}$ value complementary to the current precision limit provided by superallowed $0^+$$\rightarrow0^+$ decays. The current status of the project will be presented. [Preview Abstract] |
Saturday, October 31, 2020 10:42AM - 10:54AM |
LF.00002: An improved design for the Beta-decay Paul Trap Louis Varriano, Guy Savard, Jason A. Clark, Nicholas D. Scielzo, Dan Burdette, Mary T. Burkey, Aaron T. Gallant, Tsviki Y. Hirsh The Beta-decay Paul Trap (BPT) at Argonne National Laboratory measures the beta-neutrino angular correlation coefficient $a_{\beta \nu}$ in the pure Gamow-Teller decay of $^{8}$Li and $^{8}$B (decaying to $^{8}$Be$^* \rightarrow 2 \alpha$) to search for a tensor component of the weak interaction. The BPT has an ultimate measurement goal of 0.1% uncertainty in $a_{\beta \nu}$. Currently, the largest source of systematic uncertainty is the radiative and recoil order term corrections of the decays, which come from theory. These recoil order terms can be measured to constrain the theory corrections, but this requires a complete kinematic reconstruction of the decays. Therefore, a key source of experimental systematic uncertainty is the scattering of the emitted betas on the trap structure, hindering the kinematic reconstructions to measure these recoil order terms. In order to reduce beta scattering by a factor of 3, the existing rectangular BPT electrodes will be replaced by thin wires that approximate a quadrupole potential near the center of the trap. This new design will also reduce the required RF voltage by 30%, improving the resolution of the silicon detectors used in the experiment by reducing pick-up on them. The new design and supporting simulations will be presented. [Preview Abstract] |
Saturday, October 31, 2020 10:54AM - 11:06AM |
LF.00003: Time-reversal breaking in isospin-hindered $^{45}$K decay J.A. Behr, A. Gorelov, J.C. McNeil, A. Afanassieva, D. Melconian, M. Anholm, G. Gwinner Isospin-hindered Fermi transitions in $\beta$ decay enhance sensitivity to many sources of time-reversal violation (TRV) [Barroso and Blin-Stoyle [Phys Lett 45B 178 (1973)]. The key concept is that the TRV matrix element is compared to the Coulomb interaction's isospin-breaking matrix element, rather than to the entire decay. We are considering two isospin-hindered Fermi/Gamow-Teller decays, $^{45}$K and $^{47}$K, for which measurements of the TRV correlation $D \vec{I} \cdot \vec{v_\beta} \times \vec{v_\nu}$ are possible using TRIUMF's Neutral Atom Trap for $\beta$ decay (TRINAT). Sensitivity could be enhanced by an order of magnitude compared to the Fermi/G-T mirror decay of $^{37}$K. We would first measure the needed isospin breaking using the asymmetry of emission of the nuclear progeny with respect to the initial spin, which vanishes for pure G-T decay [J.R.A. Pitcairn et al. Phys Rev C 79 015501 (2009)] and is linear in the isospin breaking matrix element. We will also update use of GAGG scintillators for radiative beta decay TRV experiments. [Preview Abstract] |
Saturday, October 31, 2020 11:06AM - 11:18AM |
LF.00004: Branching Ratio Measurement in $^{23}$Ne Beta Decay Hitesh Rahangdale, Yonatan Mishnayot, Ben Ohayon, Vishal Srivastava, Sergey Vaintraub, Tsviki Hirsh, Jason T Harke, Nicholas D Scielzo, Aaron Gallant, Richard Hughes, Guy Ron The recoil-ion energy distribution in the decay of $^{23}$Ne among other beta emitters can be used to extract the $\beta - \nu$ angular correlation coefficient($a_{\beta\nu}$), which if measured precisely enough can be used as a probe to look for the scalar and tensor exotic couplings, absent in the standard model of physics. Here we present a precise measurement of the $\beta-\gamma$ branching ratio measurement in $^{23}$Ne $\beta$ decay to the 440 keV excited state of $^{23}$Na, which is essential for obtaining the $a_{\beta\nu}$ in $^{23}$Ne. The measurement was done using the coincidence between beta and gamma, following the beta decay of $^{23}$Ne contained in a small volume. The $^{23}$Ne was produced by $^{23}$Na(n,p)$^{23}$Ne reaction on finely ground salt(NaCl), by the neutrons obtained from the SARAF accelerator and liquid Lithium target. With the use of better detection systems than the previous measurements, we aim to achieve uncertainty of $\leq 1\%$. I will present the preliminary results obtained, which are more precise than, and are in agreement with the previous measurements. [Preview Abstract] |
Saturday, October 31, 2020 11:18AM - 11:30AM |
LF.00005: Precision Measurement of the n-235U fission cross section using the “Alpha-Gamma” Absolute Cold Neutron Flux Measurement Device CHRIS Haddock The Alpha-Gamma device at the National Institute of Standards and Technology utilizes the interaction of neutrons with a totally absorbing $^{10}$B target to precisely measure the flux of a monochromatic neutron beam. This measurement provides a calibration of the $^{6}$Li(n,$\alpha$)$^{3}$H based flux monitor used in the NIST neutron lifetime experiment to better than 0.1% and is now being utilized in novel, 0.2% level, measurements of the $^{235}$U neutron-induced fission and $^6$Li cross sections in an effort to provide systematically independent determinations of these important quantities. The results of recent and ongoing measurements will be presented, and planned operations will be discussed. [Preview Abstract] |
Saturday, October 31, 2020 11:30AM - 11:42AM |
LF.00006: Monte Carlo optimization of a low enrichment uranium neutron multiplier for the Los Alamos ultracold neutron source Robert Pattie The recent upgrade of the Los Alamos spallation driven ultracold neutron source drove the improved the statistical sensitivity of a precision measurement of the neutron lifetime and provided a path toward a new electrical dipole moment search at the $3.0 \times 10^{-27}$ e$\cdot$cm level. The output of the source can be further improve by borrowing a concept from reactor design, the fission foil neutron multiplier. The neutron flux through the cryogenic insert can be increased by replacing some of the passive room-temperature moderator components with low enrichment uranium. Simulations using MCNP6 demonstrate that the source's performance is increased by a factor of $>100$, however the heat load on the source and uranium itself will be the limiting factor. We will present the results of a simulation study to optimize a fission foil geometry that will lead to an increase of a factor of $4-10$ in the ultracold neutron production under manageable heat loads. [Preview Abstract] |
Saturday, October 31, 2020 11:42AM - 11:54AM |
LF.00007: $^{\mathrm{10}}$B Coated LYSO Screens for Detecting Ultra-Cold Neutrons. Christopher Morris UCNTau uses ultra-cold neutrons produce by the Los Alamos UCN source to measure the neutron lifetime. The neutrons are stored in the lower section of an asymmetric toroidal neutron trap constructed from a Halbach array of permanent magnets. Neutrons are confined by gravity from the top. The lifetime is measured by loading and storing neutrons from the bottom of the trap and lowering a $^{\mathrm{10}}$B coated ZnS(Ag) detector from the top to count surviving neutrons at the end of the storage period. Charged particles produced by UCN capture on the $^{\mathrm{10}}$B produce light in the ZnS, which is captured in an array of wave length shifting fibers and transported to two phototubes to count the neutrons. The long light tail produced in the ZnS introduces pileup and dead time corrections that are a limiting systematic uncertainty at the level of \textasciitilde 0.1 s, the current goal of our lifetime uncertainty. Cerium doped lutetium oxyorthosilicate/lutetium yttrium oxyorthosilicate (LYSO) is a fast, high light-output scintillator with a very small, long lifetime tail. We have produced 20x20 cm$^{\mathrm{2}} \quad^{\mathrm{10}}$B coated screens of LYSO for UCNTau. Construction techniques and tests of this new detector will be presented. [Preview Abstract] |
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