Bulletin of the American Physical Society
86th Annual Meeting of the APS Southeastern Section
Volume 64, Number 19
Thursday–Saturday, November 7–9, 2019; Wrightsville Beach, North Carolina
Session K02: Fundamental Symmetries |
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Chair: Lamlaa El Fassi, Mississippi State University Room: Holiday Inn Resort Airlie/Tidewater |
Saturday, November 9, 2019 2:00PM - 2:30PM |
K02.00001: Neutral pion radiative decay width precision measurement at Jefferson Lab Invited Speaker: Ashot Gasparian The neutral pion is the lightest strongly interacting particle in Nature. As such, the properties of $\pi^{\mathrm{0\thinspace }}$decay are especially sensitive to the underlying fundamental symmetries of quantum chromodynamics (QCD). In particular, the $\pi^{\mathrm{0}}$ decay width is primarily defined by the braking effects of axial and chiral symmetries (chiral anomaly) in QCD. Theoretical activities in this domain over the last years resulted in a high precision (1{\%} level) prediction for the $\pi^{\mathrm{0}}$ decay width. The PrimEx collaboration at Jefferson Lab has developed and performed two new experiments to measure the $\pi^{\mathrm{0}}$ decay width with high precision using the Primakoff effect. The published result from the first experiment (PrimEx-I), $\Gamma (\pi^{\mathrm{0}} \quad =$ 7.820.14(stat.) 0.17(syst.) eV, is a factor of 2.1 more precise than the previously accepted value, and it is in agreement with the chiral anomaly prediction. The second experiment (PrimEx-II) was performed in 2010 with a goal of 1.4{\%} total uncertainty to address the next-to-leading-order chiral perturbation theory calculations. The results from the PrimEx experiments will be presented and discussed in this talk. [Preview Abstract] |
Saturday, November 9, 2019 2:30PM - 3:00PM |
K02.00002: Neutrinoless Double Beta Decay Experiments: Current Status and Outlook. Invited Speaker: Igor Ostrovskiy A hypothetical second order nuclear transition --- neutrinoless double beta decay (NDBD) --- has broad implications for nuclear and particle physics. If exists, such a process would violate the lepton and B-L number conservation. Its discovery would prove that neutrinos are their own antiparticles, which would make them the only known Majorana fermions. In turn, it would be a step towards explanation of the matter-antimatter asymmetry of the Universe. This talk gives a brief overview of the existing (and recently concluded) leading experimental searches for NDBD and discusses plans for the next generation experiments, highlighting challenges, as well as potential synergies with direct dark matter searches. [Preview Abstract] |
Saturday, November 9, 2019 3:00PM - 3:30PM |
K02.00003: Qweak Ancillary Results: Exploring the Nucleus with Fundamental Symmetries Invited Speaker: Anna Lee While the primary focus of the Q$_\mathrm{weak}$ Experiment was the recently published measurement of the weak charge of the proton ($Q^p_w$) via parity-violation in elastic electron-proton scattering, many ancillary topics were also studied. This talk will cover the preliminary results for several of the ancillary measurements, all of which arose from the measurement of parity-violating asymmetries in the scattering of a longitudinally polarized electron beam from unpolarized targets. Measurements were made at two different kinematics settings (E=877 MeV, $Q^2$=0.01 GeV$^2$; E=1.16 GeV, $Q^2$=0.02 GeV$^2$) of the asymmetry in the N$\rightarrow \Delta$ transition. These measurements are sensitive to hadronic parity violation. A measurement of the asymmetry in the inelastic scattering of electrons from the proton above the resonance region (E=3.35 GeV,$Q^2$=0.082 GeV$^2$, and W=2.23 GeV) is sensitive to the $\gamma$Z electroweak correction in parity-violating elastic electron scattering. Finally, the elastic parity-violating asymmetry in electron-$^{27}$Al scattering was measured at E=1.16 GeV and $Q^2$=0.024 GeV$^2$. This result is used to determine the radius of the neutron distribution in $^{27}$Al. [Preview Abstract] |
Saturday, November 9, 2019 3:30PM - 4:00PM |
K02.00004: The search for new sources of time-reversal violation with the neutron electric dipole moment (nEDM) experiment at the Spallation Neutron Source Invited Speaker: Kent Leung A permanent neutron electric dipole moment (nEDM) is the textbook example of time-reversal symmetry violation, which is equivalent to CP-violation through the CPT theorem. Minimal Supersymmetric Standard Models are required to explain the matter content of our Universe today via baryogenesis, but these predict a nEDM $>10^{-28} e.$cm whereas the current world limit is $<3\times10^{-26}e.$cm. Therefore, a two-orders-of-magnitude improvement is a promising route for finding new physics or ruling out a sector of BSM theories. The nEDM@SNS experiment will provide this improvement using a novel technique. Nuclear magnetic resonance will be performed on polarized ultracold neutrons (UCNs) and polarized $^3$He atoms simultaneously inside two 3 L cells filled with 0.3 K superfluid $^4$He in the presence of a highly homogenous magnetic field and a strong electric field. The FNPB cold neutron beam at ORNL will produce a high UCN density inside the cell. The $^3$He serves as a cohabiting magnetometer and a live, in-situ UCN spin analyzer. Two measurement modes will be used: free double precession and critical spin dressing. These have different systematic errors and will provide us with an important self-check. Our collaboration expects to begin taking physics data towards the end of 2023. [Preview Abstract] |
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