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 MF: Mini-Symposium: Precision Beta Decay III |
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Chair: Leah Broussard, ORNL |
Saturday, October 31, 2020 2:00PM - 2:36PM |
MF.00001: Towards Fierz Interference Measurements in Neutron and $^{6}$He $\beta$ Decays Invited Speaker: X. Huyan Precision measurements in experiments with neutron and nuclear $\beta$ decays are sensitive to new physics beyond the Standard Model (SM). The signature of a possible exotic scalar or tensor contribution to the weak interaction would produce a small distortion to the $\beta$-decay energy spectrum relative to the SM prediction. To search for such a distortion, a high-precision measurement of the $\beta$-decay energy spectrum is required. Cyclotron Radiation Emission Spectroscopy (CRES) is a new elec- tron spectroscopy technique being developed by the Project 8 experiment, which is capable of measuring the energy of $\beta$ particles with high precision. This talk will explore the sensitivity potential of Fierz interference measurements in neutron and 6He decays using CRES. We will introduce the Fierz interference term and the CRES technique before presenting a survey of potential systematic uncertainties associated with CRES and their effects on the Fierz inteference term, a non-zero value of which would indicate the presence of scalar or tensor weak currents.\\ \\In collaboration with: Brent VanDevender, Pacific Northwest National Laboratory [Preview Abstract] |
Saturday, October 31, 2020 2:36PM - 2:48PM |
MF.00002: An Overview of the $^6$He CRES Experiment William Byron The $^6{\rm He}$ CRES experiment at the University of Washington CENPA aims to precisely measure the Fierz coefficient $b_{fierz}$ which parameterizes a distortion of the beta-decay spectrum that is proportional to $m/E$, the mass divided by the energy of the beta-decay electron. A measurement of $b_{fierz}$ with a $10^{-3}$ uncertainty would be competitive with current LHC measurements. The decay of $^6{\rm He}$ has a large endpoint ($Q(^6{\rm He})\approx 3.5\,MeV$) which allows for the $m/E$ distortion to vary by about a factor of 7 over the spectrum and therefore leads to high sensitivity to $b_{fierz}$. Using Cyclotron Radiation Emission Spectroscopy (CRES) (a technique demonstrated by the Project 8 collaboration) the $^6{\rm He}$ CRES experiment based at the University of Washington CENPA will have high energy resolution and be shielded from systematics that affect traditional means of electron spectroscopy. We expect to have an event rate of $\approx 1 \,{\rm event} /{\rm ms}$ and need $\sim 10^8$ events for a $10^{-3}$ measurement of $b_{fierz}$. With a few days of data we should have sufficient statistics for a competitive measurement. Hardware and software progress towards the observation of our first CRES event will be presented. [Preview Abstract] |
Saturday, October 31, 2020 2:48PM - 3:00PM |
MF.00003: Cyclotron Radiation Detection Strategy for the $^6$He CRES experiment Brent Graner The $^6$He CRES experiment at the University of Washington CENPA aims to produce a precision measurement of the Fierz interference parameter $b_{Fierz}$ by observing the cyclotron radiation of beta-decay electrons emitted in a magnetic trap. This talk will focus on our detection strategy and compare to the pre-existing CRES experiment, Project 8. Particular consideration will be given to maximizing detection bandwidth as well as the advantages that can be achieved by simultaneously observing cyclotron radiation from both directions normal to the particle orbit. [Preview Abstract] |
Saturday, October 31, 2020 3:00PM - 3:12PM |
MF.00004: Fierz Interference results and analysis from most-recent UCNA data Xuan Sun The Fierz Interference term, $b$ in the Standard Model expression of the neutron beta decay rate, acts as a probe of beyond Standard Model physics due to its sensitivity to scalar and tensor couplings. Experimentally, $b$ manifests as an energy distortion in the neutron beta decay energy spectrum. Furthermore, in the beta decay asymmetry parameter, the presence of a non-zero $b$ introduces an energy-dependent distortion in $A_0$, yielding $A_{0,b} (E)$. Using the most recent $A_0$ data from the Ultracold Neutron Asymmetry experiment (UCNA), located at Los Alamos National Laboratory (LANL), we extend the previous results on direct $b$ extraction via the energy dependence of $A_{0,b} (E)$. Furthermore, we present a supplementary analysis of the direct spectral measurements of the neutron beta decay and extract a $b$ value from that as well. Finally, we compare and contrast the advantages and limitations of these two methods of $b$ extraction. [Preview Abstract] |
Saturday, October 31, 2020 3:12PM - 3:24PM |
MF.00005: Looking for BSM Physics in Calcium-45 Beta Decay Noah Birge The Standard Model (SM) is one of the most complete theories encapsulating fundamental particle interactions. Despite its far-ranging success, neutrino flavor oscillations, the observed baryon asymmetry, the dark matter puzzle, and complete absence of gravity from the theory makes it clear that there must exist interactions and particles beyond the standard model (BSM). A measurement of the Fierz interference term in beta decay is one such candidate to test BSM physics. A nonzero Fierz term would indicate the presence of new interactions which manifest at low energy as effective scalar and tensor interactions. The strength of the coupling can be inferred from a distortion of the measured beta decay electron energy spectrum. A set of beta spectrum measurements for $^{45}$Ca was completed at the Los Alamos Neutron Science Center in 2017. I will present details of the analysis along with preliminary results. The results will entail a comparison of an extraction of the Fierz term via single-pixel and multi-pixel spectra, and a brief discussion of the dominant systematic uncertainties present. [Preview Abstract] |
Saturday, October 31, 2020 3:24PM - 3:36PM |
MF.00006: Searching for Tensor Currents in the Weak Interaction in the $\beta$-decay of $^{8}$B A. T. Gallant, N. D. Scielzo, K. Kolos, B. Alan, M. T. Burkey, L. Varriano, G. Savard, J. A. Clark, D. Gorelov, P. Mueller, M. Brodeur, D. Burrdette, K. Seigl, T. Hirsh, K. Leach, B. Maass, W. Noertershaeuser, S. T. Marley, F. Buchinger, R. Orford, D. Ray, R. E. Segel The weak interaction of the Standard Model is well-described by a vector-axial vector, or `V-A', structure, which reproduces both maximal parity violation and left-handed neutrinos in beta-decay. To search for possible tensor contributions to the weak interaction we measure the beta-neutrino correlation coefficient a$_{\beta\nu}$ in the Gamow-Teller beta-decays of $^{8}$Li and $^{8}$B. The $A = 8$ decays are ideal to probe a$_{\beta\nu}$ due to the large Q-value and delayed alpha emission from the excited state $^{8}$Be. These measurements are performed with the Beta decay Paul Trap (BPT) at Argonne National Lab. The BPT is surrounded on 4 sides with double-sided silicon strip detectors which allow the kinematics of decay products to be constrained. In this presentation we will present the first results from the decay of $^{8}$B. [Preview Abstract] |
Saturday, October 31, 2020 3:36PM - 3:48PM |
MF.00007: Progress on Using the $\beta$ Decay of Lithium-8 to Limit Tensor Currents in the Weak Interaction M. T. Burkey, A. T. Gallant, N. D. Scielzo, G. Savard, L. Varriano, J. A. Clark, R. Orford, D. P. Burdette, T. Y. Hirsh, G. H. Sargsyan, K. D. Launey, S. T. Marley, G. E. Morgan, R. Segel Analysis of a high-statistics dataset of Lithium-8 beta decay kinematics collected with the Beta Decay Paul Trap (BPT) at ANL for the purpose of precisely measuring the beta-neutrino correlation coefficient (a$_{\beta\nu}$) to probe for Tensor currents in the weak interaction has been ongoing. Lithium-8 has an essentially-pure Gamow-Teller $\beta$ decay to a broad Beryllium-8 excited state, that in turn breaks into two $\sim$1.5-MeV $\alpha$ particles. Both the energy and direction of the $\beta$ and two $\alpha$ particles are collected at the BPT, making the kinematics of each decay overdetermined. We will present the current results from this experiment, which have already constrained the tensor contribution to below 1$\%$. We will also discuss our progress to characterize the excitation-energy dependence of several recoil-order terms, which may further reduce our systematic errors. LLNL-ABS-812175 [Preview Abstract] |
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