Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session C12: Precision Measurements and Symmetry Tests |
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Sponsoring Units: GPMFC Chair: Michael Romalis, Princeton University Room: Plaza Court 1 |
Saturday, April 13, 2013 1:30PM - 1:42PM |
C12.00001: Measurement of the Planck constant using a watt balance at NIST Stephan Schlamminger, Darine Haddad, Frank Seifert, Ruimin Liu, David Newell, Jon Pratt A watt balance compares mechanical power to electrical power. Mechanical power is measured with respect to the International System of Units (SI) of the second, meter, and kilogram. Electrical measurements are made with respect to the quantum conventional electrical units based on the Josephson and von Klitzing constants as established in 1990. When used to measure electrical power, the conventional electrical units yield a value of the Planck constant, $h$. A comparison of mechanical to electrical power allows the precise determination of $h$ in SI units. International agreement of various determinations of the value of the Planck constant is a requirement for a redefinition of the SI such that the conventional electrical units become SI units. We have spent most of 2012 upgrading the existing NIST watt balance. In the past few months, we have been using the balance for a precise determination of $h$. To avoid observer's bias, the measurements have been performed blindly: The exact value of the mass used in the measurements is unknown to the experimenters. In this presentation, we will present the progress of the experiment, including some preliminary results. We will further outline the plans for the immediate future. [Preview Abstract] |
Saturday, April 13, 2013 1:42PM - 1:54PM |
C12.00002: Conditional Spin Squeezing via Quantum Non-demolition Measurements with an Optical Cycling Transition Joshua Weiner, Kevin Cox, Matthew Norcia, Justin Bohnet, Zilong Chen, James Thompson We present experimental progress towards quantum non-demolition (QND) measurements of the collective pseudo-spin $J_z$ composed of the maximal $m_F$ hyperfine ground states of an ensemble of $\sim 10^5$ $^{87}$Rb atoms confined in a low finesse $F = 710$ optical cavity. Measuring the phase shift imposed by the atoms on a cavity probe field constitutes a QND measurement that can be used to prepare a conditionally spin squeezed state. By probing on a closed optical transition, we highly suppress both fundamental and technical noise due to Raman scattering compared to probing on an open transition. It may be possible to generate spin squeezed states with $>10$ dB enhancement in quantum phase estimation relative to the standard quantum limit. The resulting spin squeezed states may specifically enable magnetic field sensing beyond the standard quantum limit as well as broadly impact atomic sensors and tests of fundamental physics. [Preview Abstract] |
Saturday, April 13, 2013 1:54PM - 2:06PM |
C12.00003: Parity violating superfluidity in ultra-cold atoms with artificial non-Abelian gauge fields Li Han, Kangjun Seo, Carlos S{\'a} de Melo We discuss the creation of parity violating Fermi superfluids in the presence of non-Abelian gauge fields realized by artificial spin-orbit coupling and crossed Zeeman fields. Unlike the case in particle physics where the parity violation is driven by weak interaction, the parity breaking is due to the effects of non-Abelian gauge fields on the kinetic energy in our system. We analyze the signatures of parity violation on the excitation spectrum of the system in normal and superfluid phases, as well as ground state properties such as the spin-resolved momentum distribution, and excitation properties such as the spin-dependent spectral function and density of states. [Preview Abstract] |
Saturday, April 13, 2013 2:06PM - 2:18PM |
C12.00004: The Compton Polarimeter in Hall C of Jefferson Amrendra Narayan A new Compton polarimeter was installed in Hall C at Jefferson Lab and used during the Qweak experiment which aims to measure the weak charge of proton with a precision of 4.1$\%$. In this polarimeter the electron beam collides with green laser light stored in a low gain Fabry-Perot Cavity; the scattered electrons are detected in 4 planes of a novel diamond micro strip detector while the back scattered photons are detected in a lead tungstate crystal. We extract the beam polarization by fitting the experimental asymmetry for each detector strip to the corresponding asymmetry calculated in QED. During the experiment, we took data to cross-calibrate Moller and Compton polarimeters in Hall C. We will share our preliminary conclusions from this comparison. In this talk, we will also present the results from Monte Carlo studies performed to estimate the systematic uncertainties of the polarization measurement along with comparing results from two independent extraction of the polarization involving very different time scales. The Compton polarimeter has achieved the design goals of 1$\%$ statistical uncertainty per hour and we expect to achieve less than 1$\%$ systematic uncertainty. [Preview Abstract] |
Saturday, April 13, 2013 2:18PM - 2:30PM |
C12.00005: The E36 Experiment at J-PARC Michael Kohl The E36 experiment is planned to run at the J-PARC K1.1BR kaon beamline in 2014-15 using a stopped kaon beam along with the TREK target and detector setup. The decay products of stopped positive kaons will be observed 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. With the aim to test lepton universality in the $K_{e2}/K_{\mu2}$ ratio with high precision, the experiment is highly sensitive to new physics beyond the Standard Model. A further goal of E36 is to search for a heavy sterile neutrino in two-body kaon decay, along with additional searches for exotic decay modes. An overview of the planned experiment, results from recent R\&D activities, and the current project status will be presented. [Preview Abstract] |
Saturday, April 13, 2013 2:30PM - 2:42PM |
C12.00006: The neutron electric dipole moment experiment at the FRM-II Michael Marino The discovery of a neutron electric dipole moment (nEDM) would provide an unambiguous indication of time violation in a fundamental system, and address one of the Sakharov conditions (CP-symmetry violation) necessary to explain the observed matter/antimatter asymmetry in the universe. Current experimental limitations on the nEDM are roughly 6 orders of magnitude above the Standard Model (SM) prediction and so searches for the nEDM provide powerful tests of physics beyond the SM. The nEDM experiment currently under construction at the FRM-II reactor in Munich is seeking to improve this limit up to 2 orders of magnitude. A contextual overview of the relevant physics will be given, and developments in the FRM-II nEDM experiment, including the recent installation of a world-record magnetically shielded room, will be presented. [Preview Abstract] |
Saturday, April 13, 2013 2:42PM - 3:18PM |
C12.00007: Francis M. Pipkin Award Talk: Proton structure from laser spectroscopy of muonic hydrogen Invited Speaker: Randolf Pohl Muonic hydrogen ($\mu$p) is the bound state of a proton and a negative muon. The large muon mass results in a small Bohr radius of the muonic hydrogen atom which in turn causes a dramatically increased sensitivity of the energy levels in $\mu$p to the finite size of the proton's charge and magnetisation distributions. The discovery of long-lived $\mu$p atoms in the metastable 2S state~[1] enabled us to perform a measurement of the 2S-2P energy splitting (Lamb shift) in muonic hydrogen for the first time~[2]. The proton radius we obtained is ten times more accurate, but $7 \sigma$ away from the current PDG value. This so-called ``proton radius puzzle'' has caused considerable activity, but no clear solution has been found yet~[3]. A second measurement in $\mu$p [4] confirms the proton radius obtained in [1], and a combination of both measurements reveals the 2S hyperfine splitting of the $\mu$p atom which is sensitive to the magnetic properties of the proton~[4].\\[4pt] [1] R.~Pohl {\it et al.}, Phys. Rev. Lett. {\bf 97}, 193402 (2006).\\[0pt] [2] R.~Pohl {\it et al.} (CREMA coll.), Nature {\bf 466}, 213 (2010).\\[0pt] [3] R.~Pohl, R.~Gilman, G.A.~Miller, K.~Pachucki, arXiv~1301.0905.\\[0pt] [4] A.~Antognini {\it et al.} (CREMA coll.), Science (2013), DOI:10.1126/science.1230016 [Preview Abstract] |
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