Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session Y13: Electroweak Nuclear Physics |
Hide Abstracts |
Sponsoring Units: DNP Chair: Steven R. Elliott, Los Alamos National Laboratory Room: Sheraton Plaza Court 2 |
Tuesday, April 16, 2019 1:30PM - 1:42PM |
Y13.00001: The Parity-Violating Asymmetry in the N→∆ Transition at Very Low Q2 Thamraa A Alshayeb The main focus of the Qweak experiment at Jefferson Lab is the recently published determination of the proton’s weak charge. In order to make corrections to the measured asymmetry at low Q2 due to inelastically scattered electrons, dedicated measurements were made of the parity violating asymmetry in the N→∆ transition at two different beam energies (877 MeV and 1.16 GeV). The measured inelastic asymmetries are used to extract the low energy constant dΔ, which is an additional physics result. The low energy constant dΔ results in a non-zero asymmetry at photon point (Q2 = 0), and is recognized as the parity violating hadronic excitation in the N→∆ transition. This has been known to be relevant to some puzzles in radiative hyperon decays. Theoretical analyses indicate potential values of dΔ much greater than its natural scale. By using the Qweak apparatus, two beam energies 877 MeV (Q2 = 0.01 GeV2) and 1.16 GeV (Q2 = 0.02 GeV2) were used in this experiment. Inelastic measurement motivations, further analysis, and preliminary results for these measurements will be presented. |
Tuesday, April 16, 2019 1:42PM - 1:54PM |
Y13.00002: Parity-Violating and Parity-Conserving Asymmetries in Electron Scattering from 27Al David S Armstrong The QWeak collaboration at Jefferson Lab has made the first measurements of parity-violating and parity-conserving single-spin asymmetries from the scattering of 1.16 GeV electrons from 27Al. The parity-violating asymmetry is sensitive to the neutral weak form factor of 27Al, which can be used to extract the radius of the neutron distribution in this nucleus. Our result is compared with a relativistic mean-field calculation by C.J. Horowitz, and provides a useful benchmark of the theoretical approach used to extract neutron skins from heavier nuclei (208Pb and 48Ca) in the upcoming PREx-II and CREx experiments. The parity-conserving asymmetry arises from two-photon exchange diagrams, and our result is compared to a calculation by M. Gorchtein, which uses the optical theorem to model the inelastic intermediate state contributions using the total photo-absorption cross section. |
Tuesday, April 16, 2019 1:54PM - 2:06PM |
Y13.00003: Maintaining a Magnetic Environment for a Nab Polarimetry Measurement Chelsea M Hendrus The Nab experiment at the Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS) aims to make precision measurements of the electron-neutrino correlation and Fierz interference term associated with the beta decay of free neutrons. Residual polarization of the incident beam presents a potential source of systematic error in this measurement. In order to understand these effects we must measure the beam polarization using polarized $^3$He gas and an Adiabatic Fast-Passage (AFP) Spin Flipper. This measurement requires control of the magnetic environment along the beamline in order to assure adiabatic spin transport of the neutrons, and prolong the polarization lifetime of the $^3$He cells. The AFP Spin Flipper is also intended to for use in mitigating the measured polarization, to within the margins our experimental error budget permits. |
Tuesday, April 16, 2019 2:06PM - 2:18PM |
Y13.00004: Precision Half-life Measurement of $^{13}$N Jacob Long, Maxime Brodeur In recent years, precision measurements have led to considerable advances in several areas of physics, including fundamental symmetry.Precise determination of $ft$ values for superallowed mixed transitions between mirror nuclides could provide an avenue to test the theoretical corrections used to extract the V$_{ud}$ matrix element from superallowed pure Fermi transitions. Calculation of the $ft$ value requires the half-life, branching ratio, and Q value. The $^{13}$N decay half-life is derived from a series of measurements of which all are over 40 years old. The life-time was determined by the $\beta$ counting of implanted $^{13}$N on a Ta foil that was removed from the beam for counting. The $^{13}$N beam was produced by a transfer reaction and separated by the TwinSol facility of the Nuclear Science Laboratory of the University of Notre Dame. The progress on the $^{13}$N analysis will be presented. |
Tuesday, April 16, 2019 2:18PM - 2:30PM |
Y13.00005: Search for Tri-Nucleon Decay in the Majorana Demonstrator Xiaoyu Zhu, Pinghan Chu, Steve Elliott, Ralph J Massarczyk The Majorana Demonstrator is an experiment searching for neutrinoless double-beta decay in 76Ge. The heavily shielded array of germanium detectors, placed nearly a mile underground at the Sanford Underground Research Facility in Lead, South Dakota, also allows searches for new exotic physics. The conservation of the baryons number is an empirical symmetry of the Standard Model. Since its violation is one of the requirements to explain the matter-antimatter asymmetry of the Universe, baryon number violation has been searched for in a variety of nuclear decay modes. One theory with an anomaly-free Z6 symmetry allows tri-nucleon decay while single- or double-nucleon decay processes are forbidden. We present the first limits for tri-nucleon decay-specific modes and invisible decay modes for Ge isotopes. The half-life limit was 4.9e25 yr for the decay 76Ge(ppn)->73Zn e+ pi+ and 4.7e25 yr for the decay 76Ge(ppp)->73Cu e+ pi+ pi+. The half-life limit was 7.5e24 yr for the invisible tri-proton decay mode of 76Ge. |
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