Bulletin of the American Physical Society
87th annual meeting of the Southeastern Section of the APS
Volume 65, Number 19
Thursday–Friday, November 5–6, 2020; Virtual
Session F01: Fundamental Symmetries II |
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Chair: Nadia Fomin, University of TN |
Friday, November 6, 2020 11:00AM - 11:12AM |
F01.00001: Recent Results from EXO-200 Timothy Daniels The detection of neutrinoless double-beta decay (0$\nu \beta \beta )$ would confirm the Majorana nature of neutrinos and shed light on the neutrino mass scale. The EXO-200 experiment employs 110 kg of active xenon enriched to 80.6% in isotope 136 in a liquid-phase time-projection chamber (TPC) in a 0$\nu \beta \beta $ search. Located underground at the Waste Isolation Pilot Plant (WIPP) outside Carlsbad, NM, the experiment collected data in two phases between May 2011 and December 2018. Analysis of the resulting 234.1 kg-yr dataset results in a lower limit on the 0$\nu \beta \beta $ half-life of 3.5x10$^{\mathrm{25}}$ yr at the 90% confidence level. The sensitivity of this low-background experiment is enhanced by the TPC technique, which exploits the anticorrelation of the ionization and scintillation signals and uses topological information to discriminate between beta-like signal events and gamma-ray backgrounds. Additional recent results, including measurements of$^{\mathrm{ 137}}$Xe beta-decay and liquid-xenon scintillation and ionization yields, will also be discussed [Preview Abstract] |
Friday, November 6, 2020 11:12AM - 11:24AM |
F01.00002: Analysis of systematic errors in the NOPTREX Experiment. Ivan Novikov, Christopher Crawford, Hejer Dhahri, William Michael Snow The Neutron Optics Parity and Time Reversal EXperiment (NOPTREX) will search for possible parity (P) and time (T) reversal invariance violating effects in propagation of polarized neutrons through a polarized target. In the proposed experiment polarization of an initially unpolarized neutron beam (P) and the asymmetry of initially polarized neutron beam (A) in propagation through a polarized target are measured. The difference between measured polarization and asymmetry would indicate the presence of PT-violating interaction. In this talk, we present analysis of various systematic uncertainties that can arise from various types of deviations from the idealized conditions. *This material is based upon work supported by the U.S. NSF under award OIA-1355438 and the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award Number DE- SC0014622. [Preview Abstract] |
Friday, November 6, 2020 11:24AM - 11:36AM |
F01.00003: Large-Nc constraints on parity-violating low-energy constants in pionless effective field theory Son Nguyen, Matthias Schindler, Roxanne Springer, Jared Vanasse References [1,2] have shown that a combination of pionless effective field theory (EFT) and the large-$N_c$ expansion, which assumes the number of colors $N_c$ to be in large, is a powerful tool for analyzing few-body hadronic parity violation (PV) at low energies. In this talk, we focus on the three-derivative operators in pionless EFT that contribute to six P-D transitions and corrections to five S-P transitions in nucleon-nucleon elastic scattering. We show that the large-$N_c$ expansion can systematically separate low-energy constants (LECs) into those that occur at leading order in $N_c$ and those that occur at next-to-leading order in $N_c$. We determine that the isoscalar and isotensor terms are dominant in the large-$N_c$ expansion. We also find that only six LECs are independent in this dual pionless EFT and large-$N_c$ expansion, yielding several relationships among the LECs. These constraints are expected to be valid at the 10\% level.\\\\ $[1]$ D. R. Phillips, D. Samart, and C. Schat, Phys. Rev. Lett. 144, 062301 (2015).\\ $[2]$ M. R. Schindler, R. P. Springer, and J. Vanasse, Phys. Rev. C 93, 025502 (2016). [Preview Abstract] |
Friday, November 6, 2020 11:36AM - 11:48AM |
F01.00004: Analysis of Two-Nucleon Magnetic and Axial Currents in a Combined Large-$N_c$ and Pionless Effective Field Theory Expansion Thomas Richardson, Matthias Schindler The combined large-$N_c$ and pionless effective field theory (EFT$_{\pi\hskip-0.40em /}$) expansion places theoretical constraints on low energy coefficients that accompany the operators of the effective theory. We obtain constraints from this framework for magnetic and axial two-nucleon contact terms. These operators contribute to a variety of electroweak processes such as the deuteron magnetic moment, radiative neutron capture, and proton-proton fusion. The large-$N_c$ expansion indicates that the isoscalar magnetic coupling is suppressed relative to the isovector coupling, which offers a partial explanation of the suppression found in data. A similar result holds for the general two-nucleon axial current which adds support for the previous omission of the isoscalar operator in processes such as neutrino-deuteron scattering. The results also imply that naturalness assumptions may be hidden depending on the choice of basis. [Preview Abstract] |
Friday, November 6, 2020 11:48AM - 12:00PM |
F01.00005: A Cryogenic Apparatus for Measuring Depolarization of Ultracold Neutrons Rifet Musedinovic, Taufique Hassan, Takeyasu Ito, Emma Jewett, Kent Leung, Mark Makela, Christopher O'Shaughnessy, Hassan Polani, Albert Young Ultracold neutrons (UCN) are utilized in a variety of sensitive experiments to probe for physics beyond the Standard Model, including investigating the neutron electric dipole moment and high precision measurements of beta decay. These experiments frequently revolve around the storage of completely polarized UCN by trapping them in material and magnetic bottles. Often storage times of a minute or longer are required to obtain the optimal sensitivity. This makes even extremely small depolarization rates crucial to measure and motivates careful testing of UCN guide materials for their depolarization properties. A cryogenic apparatus capable of studying UCN depolarization as a function of temperature and magnetic field is presented. Neutrons from the UCN source at LANSCE Area B are directed into a 6 T magnet used for polarizing UCN entering the experiment and trapping the spin-flipped UCN. The UCN then propagate through the guide system fabricated from polished copper which minimizes UCN depolarization on route to the liquid helium Cryostat where our sample lies. The apparatus is designed to run at temperatures as low as 6 K, with superconducting coils providing a maximum ambient field of 0.05 T. [Preview Abstract] |
Friday, November 6, 2020 12:00PM - 12:12PM |
F01.00006: Measurement Cell and Light Collection Simulations for the nEDM@SNS Experiment Devon Loomis A new experiment, nEDM@SNS, will search for the neutron electric dipole moment (nEDM) at the Spallation Neutron Source at Oak Ridge National Laboratory with a factor of 100 improvement in sensitivity from recent measurements. The existence of a non-zero permanent nEDM is forbidden by both Parity and Time-reversal invariance and, by the CPT theorem, a violation of CP symmetry. In the Standard Model, CP violation is handled through a complex phase in the CKM matrix. In general, extensions to the Standard Model introduce new CP violating mechanisms and predict larger nEDMs, many of which are within reach of nEDM@SNS. Thus, this probe of the CP violating sector can provide meaningful constraints on these beyond the Standard Model theories. A measured non-zero nEDM at nEDM@SNS would be a clear indication of physics beyond the Standard Model and, per Sakharov's criteria, could account for the matter-antimatter asymmetry of the universe. In this work, GEANT4 and MCNP simulations were performed to validate the design of two experiment subsystems, the light collection system and the measurement cells. We will discuss the results from these simulations that indicate a promising path towards their successful implementation in the experiment. [Preview Abstract] |
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