Bulletin of the American Physical Society
84th Annual Meeting of the APS Southeastern Section
Volume 62, Number 13
Thursday–Saturday, November 16–18, 2017; Milledgeville, Georgia
Session J3: Fundamental Symmetries |
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Chair: Nadia Fomin, University of Tennessee Room: MSU Building Donohoo Lounge |
Saturday, November 18, 2017 8:30AM - 9:00AM |
J3.00001: Frontiers and Perspectives in Low-Energy Fundamental Symmetry Tests Invited Speaker: Susan Gardner Low-energy experiments can identify physics beyond the Standard Model (SM), through either the observation of an unexpected breaking of its symmetries or that of a significant departure from a precise SM prediction. I will focus on the former, drawing a suite of examples from the precision frontier, including studies of hadron decays and searches for permanent electric dipole moments, and show how they, taken in aggregate, can speak to a bigger picture. [Preview Abstract] |
Saturday, November 18, 2017 9:00AM - 9:30AM |
J3.00002: Probing the Weak Interaction with Neutron Beta Decay Invited Speaker: Leah Broussard The neutron has proven to be an excellent tool for studying the fundamental forces of nature. Studies of the free neutron's decay to a proton, electron, and antineutrino can give us our most precise understanding of the charged weak interaction of quarks and allows us to search for hints of new physics and interactions missing from the Standard Model of Particle Physics. The next generation of experiments to measure the lifetime and angular correlations in neutron beta decay faces significant challenges to push to even higher precision and stronger limits. I will give an overview of the motivation and history of neutron beta decay, and discuss how the cutting edge experiments today are approaching these challenges. [Preview Abstract] |
Saturday, November 18, 2017 9:30AM - 10:00AM |
J3.00003: Precision Measurement of the Proton's Weak Charge Invited Speaker: David S. Armstrong The QWeak collaboration has used parity-violating elastic electron-proton scattering at very low momentum transfer to precisely measure the proton's weak charge. The weak charge is cleanly predicted within the Standard Model, with minimal theoretical uncertainty. Thus, this measurement provides an avenue for a sensitive search for beyond-the-Standard Model (BSM) physics. The final results for the weak charge will be presented, as well as the extracted values of the vector weak couplings of the up and down quarks, and the weak mixing angle. We will also discuss implications for BSM physics at the multi-TeV energy scale. [Preview Abstract] |
Saturday, November 18, 2017 10:00AM - 10:30AM |
J3.00004: A Modern Measurement of the Neutron Lifetime, Using Ultracold Neutrons in a Magneto-Gravitational Trap Invited Speaker: Chen-Yu Liu The precise value of the mean neutron lifetime plays an important role in nuclear and particle physics and cosmology. It is a key input for predicting the ratio of protons to helium atoms in the primordial universe and is used to search for new physics beyond the Standard Model of particle physics. There is a 3.9 standard deviation discrepancy between neutron lifetimes measured by counting the decay rate of free neutrons in a beam (887.7 ± 2.2 s) and by counting surviving ultracold neutrons stored for different storage times in a material trap (878.5 ± 0.8 s). I will describe the UCNtau experiment, which is designed to eliminate loss mechanisms present in previous trap experiments by levitating polarized ultracold neutrons above the surface of an asymmetric storage trap using a repulsive magnetic field gradient so that the stored neutrons do not interact with material trap walls and neutrons in quasi-stable orbits rapidly exit the trap. As a result of this approach and the use of a new in situ neutron detector, the lifetime reported here 877.7 ± 0.7 (stat) +0.3/-0.1 (sys) s is the first modern measurement of neutron lifetime that does not require corrections larger than the quoted uncertainties. [Preview Abstract] |
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