Bulletin of the American Physical Society
39th Annual Meeting of the APS Division of Atomic, Molecular, and Optical Physics
Volume 53, Number 7
Tuesday–Saturday, May 27–31, 2008; State College, Pennsylvania
Session C5: Fundamental Symmetries (Co-Sponsored by GPMFC) |
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Chair: Protik Majumder, Williams College Room: Nittany Lion Inn Boardroom I |
Wednesday, May 28, 2008 2:00PM - 2:12PM |
C5.00001: Progress Towards a New Measurement of the Permanent Electric Dipole Moment (EDM) of $^{199}$Hg T.H. Loftus, M.D. Swallows, B.R. Heckel, E.N. Fortson, W.C. Griffith, M.V. Romalis Observation of a nonzero EDM would imply CP violation beyond the Standard Model. The most precise EDM limit, established by our group several years ago for $^{199}$Hg, is $|d_{Hg}|$ $<$ 2.1$\times$10$^{-28}$ {\it e} cm. To further refine these measurements, we recently switched from two to four spin- polarized Hg vapor cells: two lie in parallel magnetic and anti- parallel electric fields, resulting in EDM-sensitive spin precession; the remaining cells, at zero electric field, serve to cancel magnetic gradient noise and limit systematics due to charging and leakage currents. To date, the statistical uncertainty for the new EDM data is $\pm$ 1.7$\times$10$^{-29}$ {\it e} cm, a 3$\times$ improvement over our previous measurement. Constraining systematics at similar levels requires mitigating Stark interference, an EDM-mimicking vector light shift that is linear in the electric field. To this end, we have explored averaging data at two probe wavelengths where the Stark interference light shift is equal but opposite. Alternatively, this effect can be eliminated by determining the Larmor frequency ``in the dark'' between two probe pulses that establish the Larmor phase at the beginning and end of the dark period. We are currently implementing this latter scheme. We will discuss progress on an improved measurement of the $^{199} $Hg EDM. [Preview Abstract] |
Wednesday, May 28, 2008 2:12PM - 2:24PM |
C5.00002: Recent Results from the PbO Electron EDM Experiment Paul Hamilton, Sarah Bickman, Yong Jiang, Hunter Smith, Amar Vutha, David DeMille We are currently taking the first data in our search for a permanent electric dipole moment (EDM) of the electron using a lead oxide (PbO) vapor cell. The existence of an EDM would imply physics beyond the standard model. We will present the current results and discuss limits on our statistical sensitivity as well as prospects for near and far term improvements. [Preview Abstract] |
Wednesday, May 28, 2008 2:24PM - 2:36PM |
C5.00003: Construction of a low-T$_{c}$ SQUID-based liquid $^{129}$Xe NMR probe for search for a permanent atomic EDM Seung-Kyun Lee, M.V. Romalis We present recent progress in construction of an ultra-high precision liquid $^{129}$Xe NMR probe designed to look for a permanent EDM of an atomic xenon. High spin density and dielectric strength in the condensed phase make an atomic liquid an attractive candidate for search for an EDM. We employ low-transition temperature (T$_{c})$ superconducting quantum interference devices (SQUIDs) for detection of low frequency ($\sim $100 Hz) Larmor precession of $^{129}$Xe and measurement of magnetic field fluctuation. We shield ambient magnetic field noise by a superconducting magnetic shield immersed in a liquid helium cryostat. A magnetic field resolution better than 1 fT/Hz$^{1/2}$ and $^{129}$Xe frequency resolution on the order of 1 nH/Hz$^{1/2}$ are expected from this design. Currently experiments are under way in a prototype setup to measure the signal-to-noise ratio and frequency stability in SQUID-detected $^{129}$Xe NMR, and to determine low-temperature leakage current under high voltage in a sapphire-based liquid xenon cell. [Preview Abstract] |
Wednesday, May 28, 2008 2:36PM - 2:48PM |
C5.00004: Status of the Radon EDM Experiment Eric Tardiff, Timothy Chupp, Wolfgang Lorenzon, Sarah Nuss-Warren, John Behr, Matthew Pearson, Kerim Gulyuz, Richard Lefferts, Norbert Pietralla, Georgi Rainovski, Jerry Sell, Gene Sprouse An experiment to measure the permanent electric dipole moment (EDM) of $^{223}$Rn is under development at TRIUMF. The EDM of $^{223}$Rn is expected to be enhanced by a factor of several hundred relative to $^{199}$Hg due to effects of octupole deformation. In the first runs, the $^{223}$Rn will be polarized by spin-exchange with laser polarized Rb and the precession frequency in combined magnetic fields will be measured using gamma-ray anisotropies detected in the large solid angle TIGRESS array of HPGe detectors. In preparation, polarization and relaxation of radon isotopes by spin exchange with laser optically pumped rubidium have been studied over the range 130$^\circ$C to 220$^\circ$C. The generation of a greater rubidium polarization in the radon spin-exchange optical pumping cells using a narrow-band diode laser is under investigation. Other preparations and the time frame for the measurements will be presented. [Preview Abstract] |
Wednesday, May 28, 2008 2:48PM - 3:00PM |
C5.00005: Prospects for using Gd$_3$Fe$_5$O$_{12}$ ferrite ceramics in searches for the electron permanent electric dipole moment and violation of local Lorentz invariance Alexander Sushkov, Stephen Eckel, Steve Lamoreaux Gadolinium iron garnet (Gd$_3$Fe$_5$O$_{12}$) ferrite ceramic maintains its high magnetic susceptibility down to cryogenic temperatures: our measurements at 4~K give $\mu=75$. This gives rise to an enhancement of material magnetization that would be induced by effects such as violation of local Lorentz invariance, or orientation of permanent electric dipole moments caused by an applied electric field. Such magnetization can be detected with DC SQUID magnetometers. Magnetic noise measurements with SQUIDs at 4~K indicate that the EDM sensitivity on the level of $10^{-28}e\cdot{\rm cm}$ is achievable after ten days of averaging. [Preview Abstract] |
Wednesday, May 28, 2008 3:00PM - 3:12PM |
C5.00006: Search for the electron's electric dipole moment with a cold molecular beam of ThO Amar C. Vutha, O. Keith Baker, Wesley C. Campbell, David DeMille, John M. Doyle, Gerald Gabrielse, Yulia V. Gurevich, Maarten A.H.M. Jansen We describe a method for an improved search for the electric dipole moment (EDM) of the electron, using a cold molecular beam of thorium monoxide (ThO). We identify the metastable H state in ThO as being highly sensitive to the CP-violating EDM of the electron. ThO in a beam is shown to have excellent properties for rejection of systematic errors and for efficient state preparation and detection. We report on recent progress in the production of cold ThO molecules and measurement of the lifetime of the H state. [Preview Abstract] |
Wednesday, May 28, 2008 3:12PM - 3:24PM |
C5.00007: On the possibility of an eEDM experiment in ThO Edmund Meyer, John Bohn The observation of an electron electric dipole moment (eEDM) would have major ramifications for the standard model of physics. Diatomic polar molecules offer perhaps the best opportunity to effectively apply large electric fields (${\bf F}_{\rm eff} \sim 10$'s of Gv/cm) to an electron. In general, estimating the size of this field for a given molecule requires a detailed, relativisitc many-body structure calculation. Recently we have shown that we can estimate ${\bf F}_{\rm eff}$ reasonably using perturbation theory and nonrelativistic calculations, which means molecules can be evaluated much more quickly for their suitability for an eEDM search\footnotemark[1]. In this talk, we present a further improvement to the method. As an initial result, we apply this method to ThO, a molecule with a low-lying $^3\Delta$ electronic state. The value of ${\bf F}_{\rm eff}$ is approximately 70\,GV/cm and offers one of the best known candidates yet for the eEDM search. \footnotetext[1]{E. R. Meyer, J. L. Bohn and M. P. Deskevich, Phys. Rev. A {\bf 73}, 062108 (2006)} [Preview Abstract] |
Wednesday, May 28, 2008 3:24PM - 3:36PM |
C5.00008: Search for long-range anomalous spin dependent forces using a K-$^{3}$He co-magnetometer Georgios Vasilakis, Justin M. Brown, Thomas W. Kornack, Michael V. Romalis Various theories propose new long-range forces. We test the existence of long range spin dependent forces between neutrons. We use a K-$^{3}$He co-magnetometer with a sensitivity of 1 fT/Hz$^{1/2}$ and a spin-source of hyperpolarized $^{3}$He gas with about 10$^{22}$ polarized spins. The co-magnetometer is insensitive to ordinary magnetic fields but sensitive to interactions with anomalous coupling to electronic or nuclear spin. Nuclear spin polarization of a 12 amagat $^{3}$He cell is achieved through spin exchange optical pumping. The separation of the spin-source from the co-magnetometer is approximately 50 cm. The $^{3}$He spin polarization is reversed using Adiabatic Fast Passage every 10 sec with losses of about 2$\times $10$^{-5}$ per flip. We look for a signal in the co-magnetometer correlated with the modulation of the spin source. Present sensitivity of the experiment to the neutron spin coupling constant (g$_{n}^{2}$/4$\pi )$ for light pseudoscalar particles is in the range of 10$^{-9}$, about an order of magnitude better than existing limits from gravitational weak equivalence principle and inverse square law tests, with further improvement anticipated. [Preview Abstract] |
Wednesday, May 28, 2008 3:36PM - 3:48PM |
C5.00009: Bounds on New Spin Dependent Forces Between Neutrons Using a $^3$He / $^{129}$Xe Zeeman Maser Alex Glenday, Claire Cramer, David F. Phillips, Ronald L. Walsworth Searches for new spin dependent macroscopic forces place bounds on physics beyond the Standard Model, such as Lorentz symmetry violation and existence of new particles like the axion. We report the first experimental limits on new spin dependent macroscopic forces between neutron spins. We measure the nuclear Zeeman frequencies of a $^3$He / $^{129}$Xe maser while we modulate the nuclear spin polarization of $^3$He in a separate glass cell. We place limits on the coupling strength of dipole potentials mediated by axion-like particles ($g_pg_p$) at the $5.5\times10^{-6}$ level for interactions at ranges longer than 40 cm. [Preview Abstract] |
Wednesday, May 28, 2008 3:48PM - 4:00PM |
C5.00010: Measurement of the Beta-Neutrino Correlation of $^{21}$Na Using Shakeoff Electrons P. Vetter, J.R. Abo-Shaeer, S.J. Freedman, R. Maruyama We have measured the \mbox{$\beta - \nu$} correlation coefficient, $a_{\beta\nu}$, in $^{21}$Na using a laser-trapped sample. We measure the energy spectrum of the recoil nuclei by measuring their time-of-flight in coincidence with the atomic electrons shaken off in beta decay. High detection efficiency of these low-energy electrons allows good counting statistics, even with low trap density. Low trap density suppresses photoassociation to molecular sodium, which can cause a large systematic error in the beta decay correlation. Our measurement, $a_{\beta\nu} = 0.5502(60)$ with a 1\% fractional uncertainty, agrees with the Standard Model prediction $a_{\beta\nu} = 0.553(2)$, but disagrees with our previous measurement which was susceptible to error introduced by molecular sodium. We summarize precise measurements of $a_{\beta\nu}$ and their consequences for searches for Beyond Standard Model scalar and tensor current couplings. We will make a few remarks about the future of precision measurements of beta decay using optical traps. [Preview Abstract] |
Wednesday, May 28, 2008 4:00PM - 4:12PM |
C5.00011: Nuclear Spin-Dependent Parity Nonconservation in Diatomic Molecules David Rahmlow, Dennis Murphree, Sidney Cahn, David Demille, Edward Deveney, Richard Paolino, Misha Kozlov Nuclear spin-dependent parity nonconservation (NSD-PNC) effects arise from couplings of the $Z_0$ boson (parameterized by the electroweak coupling constants $C_{2P,N}$) and from the interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The effects of the anapole moment scale with the nucleon number A of the nucleus as $A^{2/3}$, while the $Z_0$ coupling is independent of A; the former will be the dominant source of NSD-PNC in nuclei with A $>$ 20. To date, the most precise result on NSD-PNC comes from a measurement of the hyperfine dependence of atomic PNC in $^{133}Cs$. However, the effects of NSD-PNC can be dramatically enhanced in diatomic molecules. We outline an experimental program to take advantage of this enhancement. We have identified over ten suitable molecules; from measurements on the nuclei in these molecules we can extract the relative contributions of the anapole moment and the electroweak $Z_0$ couplings. This will increase the available data on nuclear anapole moments, as well as reduce the uncertainties in current measurements of $C_{2N}$ and $C_{2P}$. We report on the design of our pulsed molecular beam experiment and the current status of our efforts. [Preview Abstract] |
Wednesday, May 28, 2008 4:12PM - 4:24PM |
C5.00012: Development of the CI + all-order method for atomic calculations Marianna Safronova, Mikhail Kozlov, Walter Johnson The development of the relativistic all-order method where all single and double excitations of the Dirac-Hartree-Fock wave function are included to all orders of perturbation theory led to accurate predictions for energies, transition amplitudes, hyperfine constants, and other properties of monovalent atoms. The all-order method is designed to treat core-core and core-valence correlations with high accuracy. Precision calculations for atoms with several valence electrons require an accurate treatment of the very strong valence-valence correlation; a perturbative approach leads to significant difficulties. In this work, we develop a novel method for precision calculation of properties of atomic systems with more than one valence electron. This method combines the all-order approach currently used in precision calculations of properties of monovalent atoms with the CI approach. The preliminary results for divalent systems are presented. [Preview Abstract] |
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