Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session C04: New Insights from Precision Measurements of Weak Interaction PhenomenaInvited Live
|
Hide Abstracts |
Sponsoring Units: GPMFC DNP Chair: Susan Gardner, University of Kentucky Room: Washington 3 |
Saturday, April 18, 2020 1:30PM - 2:06PM Live |
C04.00001: Results from the aSPECT experiment Invited Speaker: Stefan Baessler We report on a precise measurement of the antineutrino-electron angular correlation (the $a$ coefficient) in free neutron beta-decay from the $a$SPECT experiment. The $a$ coefficient is inferred from the recoil energy spectrum of the protons which are detected in $4\pi$ by the $a$SPECT spectrometer using magnetic adiabatic collimation with an electrostatic filter. Data are presented from a 100 days run at the Institut Laue Langevin in 2013. The sources of systematic errors are considered and included in the final result. We obtain $a = -0.10430(84)$ which is the most precise measurement of the neutron $a$ coefficient to date. From this, the ratio of axial-vector to vector coupling constants is derived giving $\lambda = -1.2677(28)$, in slight tension with other results.\\ \\In collaboration with: F. Ayala Guardia, M. Borg, J. Kahlenberg, R. Munoz Horta, C. Schmidt, A. Wunderle, W. Heil (Institut fuer Physik, Johannes Gutenberg-Universitaet Mainz, 55128 Mainz, Germany), R. Maisonobe, M. Simson, T. Soldner, R. Virot, O. Zimmer (Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France), M. Klopf, G. Konrad (Technische Universitaet Wien, Atominstitut , 1020 Wien, Austria), S. Baessler (Department of Physics, University of Virginia, Charlottesville, VA 22904, USA and Oak Ridge National Lab, Bethel Valley Road, Oak Ridge, TN 37831, USA), F. Glueck (Institut fuer Kernphysik (IKP), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany), U. Schmidt (Physikalisches Institut, Universitaet Heidelberg, 69120 Heidelberg, Germany) [Preview Abstract] |
Saturday, April 18, 2020 2:06PM - 2:42PM Live |
C04.00002: Discrepancy between experimental and theoretical $\beta$-decay rates resolved from first principles Invited Speaker: Thomas Papenbrock The dominant decay mode of atomic nuclei is $\beta$-decay, a process that changes a neutron into a proton (and vice versa). This decay offers a window to physics beyond the standard model, and is at the heart of microphysical processes in stellar explosions and element synthesis in the Universe. However, observed $\beta$-decay rates in nuclei have been found to be systematically smaller than for free neutrons: this 50-year old puzzle about the apparent quenching of the fundamental coupling constant by a factor of about 0.75 is without a first-principles theoretical explanation. This talk demonstrates that this quenching arises to a large extent from the coupling of the weak force to two nucleons as well as from strong correlations in the nucleus. State-of-the-art computations of $\beta$-decays, based on effective field theories of the strong and weak forces and powerful quantum many-body techniques, show that the quenching puzzle is solved from light- and medium-mass nuclei to $^{100}$Sn. The results, published as [P. Gysbers, G. Hagen, J. D. Holt, G. R. Jansen, T. D. Morris, P. Navratil, T. Papenbrock. S. Quaglioni, A. Schwenk, S. R. Stroberg, and K. A. Wendt, Nature Physics 15, 428 (2019)], are consistent with experimental data and have implications for heavy element synthesis in neutron star mergers and predictions for the neutrino-less double-$\beta$-decay, where an analogous quenching puzzle is a source of uncertainty in extracting the neutrino mass scale. [Preview Abstract] |
Saturday, April 18, 2020 2:42PM - 3:18PM Not Participating |
C04.00003: Measurement of two-neutrino double electron capture in $^{124}$Xe Invited Speaker: Elena Aprile Two-neutrino double electron capture (2$\nu$ECEC) is a second-order weak process with predicted nuclear half-lives that surpass the age of the Universe by many orders of magnitude. Indications for 2$\nu$ECEC decays have only been seen for two isotopes, $^{78}$Kr and $^{130}$Ba, and instruments with very low background levels are needed to detect them directly with high statistical significance. The 2$\nu$ECEC half-life provides an important input for nuclear structure models and its measurement represents a first step in the search for neutrinoless double electron capture (0$\nu$ECEC). A detection of the latter would imply the existence of lepton number violation and the Majorana nature of neutrinos. The XENON1T dark matter experiment recently reported the first direct observation of the 2$\nu$ECEC in $^{124}$Xe. The significance of the signal is $4.4$ standard deviations, and the measured half-life, $(1.8 \pm 0.5_\mathrm{stat} \pm 0.1_\mathrm{syst}) \times 10^{22}$ yr, is the longest ever measured directly . This highlights the broad physics reach for the next experiment in the XENON family, XENONnT, which will start data-taking in 2020. \newline This talk is based on \emph{Observation of two-neutrino double electron capture in $^{124}$Xe with XENON1T}, [XENON Collaboration. Nature 568, 532-535 (2019)] [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700