Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session E6: Fundamental Symmetries II |
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Sponsoring Units: GPMFC DNP Chair: Jaideep Singh, Michigan State University Room: Key 2 |
Saturday, April 11, 2015 3:30PM - 3:42PM |
E6.00001: Searches for Lorentz and CPT Violation with Fermions in Penning Traps Yunhua Ding, V. Alan Kosteleck\'y A theoretical analysis is performed of the prospects for detecting Lorentz and CPT violation in Penning-trap experiments with trapped particles and antiparticles. Using the general effective field theory called the Standard-Model Extension, we study signals in anomaly and cyclotron frequencies arising from Lorentz- and CPT-violating operators of arbitrary mass dimensions. Constraints on coefficients for Lorentz and CPT violation are extracted from existing data, and sensitivities attainable in forthcoming Penning-trap experiments are discussed. [Preview Abstract] |
Saturday, April 11, 2015 3:42PM - 3:54PM |
E6.00002: Prospects for Lorentz violation in atomic spectroscopy and spin-precession experiments Arnaldo J. Vargas, V. Alan Kosteleck\'y A breaking of Lorentz symmetry has been suggested as a low-energy signature for theories beyond the Standard Model and General Relativity. In this talk, signals of Lorentz violation in atomic spectroscopy and spin-precession experiments are discussed. The analysis is based on the general effective field theory known as the Standard-Model Extension, including contributions from operators with renormalizable and nonrenormalizable mass dimensions. Possible signals for Lorentz violation are identified, including several classes of time variations of the measured frequencies. Effects of CPT violation in matter-antimatter comparisons are also considered. Bounds on coefficients for Lorentz violation are obtained using existing analyses of muon and electron experiments, and estimates of sensitivities in future experiments are presented. [Preview Abstract] |
Saturday, April 11, 2015 3:54PM - 4:06PM |
E6.00003: South Pole Lorentz Invariance Test Morgan Hedges, Marc Smiciklas, Michael Romalis Tests of Lorentz and CPT symmetries are important because they form a cornerstone of quantum field theory and general relativity. To test one of the consequences of local Lorentz invariance we have performed a precision test of spatial isotropy at the Amundsen-Scott station near the geographic South Pole. This location provides the most isotropic environment available on Earth. We use an atomic spin co-magnetometer to compare energy levels in $^{21}$Ne and Rubidium atoms as the apparatus rotates with respect to the cosmos. Our experimental sensitivity is more than an order of magnitude greater than in previous such measurements, known as Hughes-Drever experiments. By operating at the South Pole we eliminate background signals due to the gyroscopic interactions of spins with Earth's rotation as well as diurnal environmental effects. The experiment has finished a 2-year data collection period and we expect to present the final results at the meeting. This is the first precision atomic physics experiment performed at the Pole and we will discuss the potential for future such measurements. [Preview Abstract] |
Saturday, April 11, 2015 4:06PM - 4:18PM |
E6.00004: On measurement of the isotropy of the maximum attainable speed Bogdan Wojtsekhowski A proposal for a precision experiment to investigate possible anisotropy of the maximum attainable speed (MAS) will be presented. It is based on an electron/positron beam with a large Lorentz factor and a 180-degree magnetic arc. The ratio of the momenta at the two ends of the magnetic arc will be used to form an observable which is sensitive to the MAS variation and immune to most of the instabilities of the apparatus. The search will use the sidereal periodicity of a potential signal. The uncertainty of momenta measurement could be greatly reduced by means of the electron and positron beams simultaneously rotating in the same magnetic system. The projected sensitivity of the measurement and the implications will be discussed. [Preview Abstract] |
Saturday, April 11, 2015 4:18PM - 4:30PM |
E6.00005: ABSTRACT WITHDRAWN |
Saturday, April 11, 2015 4:30PM - 4:42PM |
E6.00006: Construction of a new watt balance with the goal to realize the kilogram in the US Stephan Schlamminger, Darine Haddad, Frank Seifert, Leon Chao, David Newell, Jon Pratt A watt balance is a mechanical device that compares mechanical power to electrical power. Since electrical power is measured using quantum physics by employing the Josephson effect and the Quantum Hall effect, electrical power can be measured as a product of a known factor, two frequencies, and the Planck constant $h$. Mechanical power is given by $mgv$, where $m$ is the mass of a weight, $g$ the local acceleration, and $v$ the velocity. Hence, the watt balance provides a link between mass and Planck's constant. Currently several watt balances worldwide are employed to measure $h$. A redefinition of the international system of units (SI) is currently in discussion and may become reality as early as 2018. In the new SI, the numerical value of the Planck constant will be fixed and the watt balance is a means to realize the unit of mass. Researchers at NIST are preparing for a new SI and we have started in 2011 with plans to design a new watt balance capable of realizing the kilogram with relative uncertainties of a few parts in $10^8$. Construction of the new watt balance has started in 2014. In my talk, I will show some of the latest results achieved with this apparatus. [Preview Abstract] |
Saturday, April 11, 2015 4:42PM - 4:54PM |
E6.00007: Status of the TREK/E36 Experiment at J-PARC Michael Kohl The TREK/E36 experiment will provide a precision test of lepton universality in the $K_{e2}/K_{\mu2}$ ratio to search for new physics beyond the Standard Model. Simultaneously it will search for light U(1) gauge bosons and sterile neutrinos below 300 MeV/c$^2$, which could be associated with dark matter or explain established muon-related anomalies such as the muon anomalous magnetic moment and the proton radius puzzle. The experiment is scheduled to run in 2015 at the J-PARC K1.1BR kaon beamline. It uses a scintillating fiber target to stop a beam of up to $10^6$ positive kaons per second. The kaon decay products are detected with a large-acceptance toroidal spectrometer capable of tracking charged particles with high resolution, combined with a photon calorimeter with large solid angle and redundant particle identification systems. An overview of the planned experiment and the current project status will be presented. [Preview Abstract] |
Saturday, April 11, 2015 4:54PM - 5:06PM |
E6.00008: Calculation of higher order corrections to the positronium hyperfine splitting Gregory Adkins, Richard Fell The positronium ground state hyperfine splitting (hfs) has long been of interest as a high-precision test of our understanding of binding in QED. The positronium hfs is particularly sensitive to recoil effects (because the ratio of masses is one) and to virtual electron-positron annihilation, but positronium is insensitive to strong and weak interaction effects. Consequently, the comparison between theory and experiment for the positronium hfs, and more generally the positronium spectrum, tests different aspects of the theory compared to comparisons in other exotic atoms. For the past fifteen years there has been a persistent discrepancy between predicted and measured values of the positronium hfs of about four standard deviations--although a new experimental result is consistent with present theory. Recent experimental work is leading to new high-precision measurements, and the calculation of corrections at order $m \alpha^7$ has begun. We report on the status of the positronium hfs problem and a discussion of recent progress. [Preview Abstract] |
Saturday, April 11, 2015 5:06PM - 5:18PM |
E6.00009: The Axion Resonant InterAction Detection Experiment (ARIADNE) Andrew Geraci Axions are particles predicted to exist in order to explain the apparent smallness of the neutron electric dipole moment. While also being promising candidates for dark matter, in tabletop experiments axions can mediate short-range spin-dependent forces between objects. I will describe a new experiment for detecting short-range forces from axion-like particles based on nuclear magnetic resonance in hyperpolarized Helium-3. The method can potentially improve previous experimental bounds by several orders of magnitude and can probe deep into the theoretically interesting regime for the QCD axion, over a range that is complementary to existing axion search experiments.[1] A. Arvanitaki and A. Geraci, Phys. Rev. Lett. 113, 161801 (2014). [Preview Abstract] |
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