Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session CB: Fundamental Symmetries in the LHC Era |
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Chair: Richard Van de Water, Los Alamos National Laboratory Room: Sweeney Ballroom A |
Thursday, October 29, 2015 8:30AM - 9:06AM |
CB.00001: UCNtau: A Precision Measurement of the Neutron Beta-Decay Lifetime Invited Speaker: Chen-Yu Liu Eighty years after Chadwick discovered the neutron, physicists today still debate over how long the neutron lives. Measurements of the neutron lifetime have achieved the 0.1\% level of precision ($\sim$ 1 s), however, experiments using the bottle technique yield lifetime results systematically lower than those using the beam technique. Measuring the neutron lifetime is difficult due to several limitations: the low energy of the decay products, the inability to track slow neutrons, and the fact that the neutron lifetime is long ($880.3 \pm 1.1$ s, PDG2014). In particular, slow neutrons are susceptible to many loss mechanisms other than beta-decay, such as upscattering and absorption on material surfaces; they act on time scales comparable to the neutron beta-decay and thus make the extraction of the beta-decay lifetime very challenging. In the UCN$\tau$ experiment, we trap ultracold neutrons (UCN) in a magnetic-gravitational trap. The apparatus, installed at the Los Alamos UCN source, has been used to develop new techniques--using field confinements with attentions to the phase space evolution of trapped neutrons--with an aim to reduce the uncertainty to 1 s (and better). I will report first competitive results and discuss plans to quantify systematic effects. [Preview Abstract] |
Thursday, October 29, 2015 9:06AM - 9:42AM |
CB.00002: Neutrino-nucleus scattering in the quasi-elastic region Invited Speaker: Stefano Gandolfi Several upcoming experiments have the ambitious goal to understand neutrino mixing, including the mass hierarchy and CP violation, to search for physics beyond the standard model. These experiments aim to reach a precision at the per-cent level, and, in order to accurately interpret these measurements, the knowledge of the neutrino-nucleus interaction is critical. In this talk we will present recent Green's Function Monte Carlo calculations of the euclidean correlation functions that are relevant for the neutrino-12C scattering in the quasi-elastic region. These non-perturbative calculations fully include long- and short-range correlations in the nuclear wave function, and give an excellent description of properties of light nuclei. We will show that the inclusion of two-body operators consistent with the nuclear Hamiltonian is crucial and their contribution is quite sizable, as already predicted by similar calculations and experimental measurements of electron-scattering. These contributions are necessary to understand electron scattering and are also very important in neutrino-nucleus scattering. [Preview Abstract] |
Thursday, October 29, 2015 9:42AM - 10:18AM |
CB.00003: The Amazing Electron and it Moments: Most Precise Tests of the Standard Model and Proposed Fixes Invited Speaker: Gerald Gabrielse The Standard Model of particle physics is the great triumph and great frustration of modern physics. It predicts the value of the electron magnetic moment -- the most precisely measured property of an elementary particle -- to better than a part per trillion. Yet, it cannot explain why a universe made of matter survived the big bang, nor can it yet explain dark matter or dark energy. A number of adjustments to the Standard Model have been proposed. To test these our ACME collaboration recently completed a 12 times more sensitive measurement of the electron's electric dipole moment. The Standard Model predicts a moment too small to measure, while proposed adjustments (e.g. supersymmetric models) generally cannot avoid predicting an electric dipole moment that could be within range of this new measurement sensitivity. [Preview Abstract] |
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