Bulletin of the American Physical Society
APS April Meeting 2022
Volume 67, Number 6
Saturday–Tuesday, April 9–12, 2022; New York
Session Z11: Fundamental SymmetriesRecordings Available
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Sponsoring Units: DNP Chair: Evangeline Downie, George Washington University Room: Majestic |
Tuesday, April 12, 2022 3:45PM - 3:57PM |
Z11.00001: Precision Measurement of the η →γγ Decay Width via the Primakoff Effect Liping Gan The η →γγ decay offers a sensitive probe for understanding QCD symmetries and the origin and the dynamics of QCD symmetry breaking. A precision measurement of the Γ(η →γγ ) width via the Primakoff effect (the PrimEx-eta experiment) is currently on-going in Hall D at Jefferson Lab. Two data sets were collected in 2019 and 2021, and the third run will be expected in 2022. This decay width will be extracted from measured differential cross sections at forward angles on light nuclear targets, using a tagged photon beam with energies up to 11.7 GeV. Results of this experiment will not only potentially resolve a long-standing discrepancy between the previous Primakoff and the collider measurements, but will also reduce the experimental uncertainty by a factor of two on the average value of existing results listed in the Particle Data Group. It will directly improve all other η partial decay widths which rely on the accuracy of the η radiative decay width. The projected 3.2% precision on Γ(η →γγ ) for PrimEx-eta will have a significant impact on the determination of the fundamental QCD parameters, such as the light-quark mass ratio and the η-η mixing angle; and will offer a critical input for theoretical calculation of hadronic light-by-light contribution in the muonic g-2. The experimental status and a preliminary result of the η yield reconstructed from the two-photon final state will be presented. |
Tuesday, April 12, 2022 3:57PM - 4:09PM |
Z11.00002: Search for New Physics With an Invariant Mass of 10-20 MeV at ARIEL Ross Corliss Reported anomalies in 4He and 8Be transitions, along with the disagreement between calculation and measured values of muonic g-2, which have been recently reiterated by the Fermliab g-2 experiment, have heightened interest in a potential new particle near 17 MeV. To be compatible with current limits, this particle would need to be proto-phobic, and hence suppressed in hadronic production. Leptonic searches, such as production and decay in electron-nucleus scattering, eX -> eXA' -> eXee+, can test leptonic couplings directly. As the first step toward mounting such a search, the DarkLight collaboration has installed a test chamber in TRIUMF's ARIEL accelerator. The status of these beam tests will be discussed, as will details of the spectrometer that will be installed in the next stages of the experiment along with its expected sensitivities to new physics. |
Tuesday, April 12, 2022 4:09PM - 4:21PM |
Z11.00003: Search for Light Neutral Bosons in the TREK/E36 Experiment Dongwi H Dongwi The Standard Model (SM) represents our best description of the subatomic world and has been very successful in explaining how elementary particles interact under the influence of the fundamental forces. Despite its far reaching success in describing the building blocks of matter, the SM is still incomplete; falling short to explain dark matter, baryogenesis, neutrino masses and much more. The E36 experiment was conducted at J-PARC in Japan, it was designed to test lepton universality, and it has additional sensitivity to search for light U(1) gauge bosons. Of particular interest is the muonic K+ decay channel. Such $U(1)$ bosons could be associated with dark matter or explain established muon-related anomalies such as the muon $g-2$ value, and perhaps the proton radius puzzle. A realistic simulation study was employed for these rare searches in a mass range of 20 MeV$/c^2$ to 110 MeV$/c^2$. Preliminary upper limits for the $A^\prime$ branching ratio $\mathcal{B}r(A^\prime)$ extracted at 95\% CL will be presented. |
Tuesday, April 12, 2022 4:21PM - 4:33PM |
Z11.00004: Measurement of Neutron Polarization and Transmission for the nEDM@SNS Experiment. Kavish Imam The neutron electric dipole moment experiment at the Spallation Neutron Source (nEDM@SNS) will implement a novel method, which utilizes polarized ultra-cold neutrons (UCN) and polarized 3He in a bath of superfluid 4He, to place a new limit on the nEDM down to 2-3x10-28 e·cm. The experiment will employ a cryogenic magnet and magnetic shielding package to provide the required magnetic field environment to achieve the proposed sensitivity. This talk will describe the design and implementation of a 3He polarimetry setup at the SNS to measure the neutron polarization and transmission losses resulting from passage through the magnetic shielding and cryogenic windows. |
Tuesday, April 12, 2022 4:33PM - 4:45PM |
Z11.00005: Spin Transport Coil Tests for the nEDM@SNS Experiment Cory A Smith, Christopher B Crawford, Ahmad Saftah, Mark H McCrea, Jon Mills, ZACHARY J MISTELSKE, Joseph Peck The nEDM@SNS experiment relies on polarized He-3 as a comagnetometer and analyzer of the neutron spin precession. The He-3 is introduced into the precession cell from an atomic beam source outside the passive magnetic shield via a system of electromagnetic transport coils. I will describe a prototype passive shield for testing these coils and their interaction with the shield. |
Tuesday, April 12, 2022 4:45PM - 4:57PM |
Z11.00006: Precison Measurements of 8B Beta Decay: Solar Neutrinos and Physics Beyond the Standard Model Brenden Longfellow, Aaron T Gallant, Tsviki Y Hirsh, Mary T Burkey, Guy Savard, Nicholas D Scielzo, Ralph E Segel, Louis Varriano, Maxime Brodeur, Daniel P Burdette, Daniel D Lascar, Peter Mueller, Dwaipayan Ray, Kumar S Sharma, Adrian A Valverde, Gemma L Wilson, Xinliang Yan The beta decay of 8B provides exceptional sensitivity to physics beyond the Standard Model and is the dominant source of the high-energy neutrinos generated in the Sun and observed on Earth. A high-statistics experiment was performed at Argonne National Laboratory using the Beta-decay Paul Trap (BPT) surrounded by four double-sided silicon strip detectors to measure alpha and beta particle energies from the beta decay of 8B to 8Be, which breaks up into two alpha particles. Through precise measurements of the kinematics of the decay products, limits on the exotic tensor current contribution to the weak interaction can be determined. Additionally, the decay product kinematics can be leveraged to reconstruct the undistorted 8B neutrino energy spectrum, a necessary ingredient for experiments aiming to precisely measure solar neutrino oscillations. Preliminary results for both the tensor current limit and the neutrino spectrum will be presented. |
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