Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session DG: Mini-symposium on Hadronic Weak InteractionMini-Symposium
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Chair: Nadia Fomin, University of Tennessee Room: Pavilion Ballroom B |
Friday, October 14, 2016 10:30AM - 11:06AM |
DG.00001: A New Era of Symmetries in the Hadronic Interaction Invited Speaker: Christopher Crawford The search for a weak component of the nuclear force began in 1957, shortly after the proposal of parity violation. While it has been observed in compound nuclei with large nuclear enhancements, a systematic characterization of the hadronic weak interaction is still forthcoming almost sixty years later. New experimental facilities and technology have rejuvenated efforts to map out this "complexity frontier" within the Standard Model, and we will soon have precision data from multiple few-body experiments. In parallel, modern effective field theories have provided a systematic model independent description of the hadronic interaction with estimates of higher-order effects. The characterization of discrete symmetries in hadronic systems has recently become important for the design and analysis of other precision symmetries measurements, for example, electron PV scattering and time-reversal violation experiments. These new developments in experiment, theory, and application have ushered in a new era in hadronic parity violation. [Preview Abstract] |
Friday, October 14, 2016 11:06AM - 11:18AM |
DG.00002: Parity violation in few-nucleon systems within a chiral effective field theory framework Michele Viviani We study the effect the nucleon-nucleon parity violation (PV) interaction, induced by the weak interaction between quarks, in few-nucleon systems. First, we discuss the derivation of the nucleon-nucleon PV interaction within a chiral effective field theory framework, in particular its extension to next-to-next-to-leading order (N2LO), recently reported in J. de Vries et al., Eur. Phys. J. A 50, 108 (2014). We report on an alternative derivation of this N2LO PV interaction using our technique based on the time-ordered perturbation theory, accounting also for cancellations between the contributions of irreducible diagrams and the contributions due to non-static corrections from energy denominators of reducible diagrams. Ultraviolet divergences associated with the loop corrections are isolated in dimensional regularization. A detailed analysis of the number of independent low-energy constants (LEC's) entering the potential is carried out. Then, we investigate PV effects induced by this updated potential on several few-nucleon observables, including the $\vec{p}\,$-$p$ longitudinal asymmetry, the neutron spin rotation in $\vec{n}$-$p$ and $\vec{n}$-$d$ scattering, and the longitudinal asymmetry in the $^3$He$(\vec{n},p)^3$H charge-exchange reaction. [Preview Abstract] |
Friday, October 14, 2016 11:18AM - 11:30AM |
DG.00003: ABSTRACT WITHDRAWN |
Friday, October 14, 2016 11:30AM - 11:42AM |
DG.00004: Nuclear Spin Dependent Parity Violation in Diatomic Molecules Sidney Cahn, Emine Altuntas, David DeMille Nuclear spin-dependent parity violation (NSD-PV) effects arise from exchange of the $Z^{0}$ boson between electrons and the nucleus, and from interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The latter scales with nucleon number of the nucleus $A$ as $A^{2/3}, $whereas the $Z^{0}$ coupling is independent of $A$. Thus the former is the dominant source of NSD-PV for nuclei with $A\ge $\textit{20}. We study NSD-PV effects using diatomic molecules, where signals are dramatically amplified by bringing rotational levels of opposite parity close to degeneracy in a strong magnetic field. The NSD-PV interaction matrix element is measured using a Stark-interference technique. We present results that demonstrate statistical sensitivity to NSD-PV effects surpassing that of any previous atomic parity violation measurement, using the test system~$^{\mathrm{138}}$Ba$^{\mathrm{19}}$F. We report our progress on measuring and cancelling systematic effects due to combination of non-reversing stray $E$-fields, $E_{nr}$ with $B$-field inhomogeneities. Short-term prospects for measuring the nuclear anapole moment of $^{\mathrm{137}}$Ba$^{\mathrm{19}}$F are discussed. In the long term, our technique is sufficiently general and sensitive to enable measurements across a broad range of nuclei. [Preview Abstract] |
Friday, October 14, 2016 11:42AM - 11:54AM |
DG.00005: Status of the NPDGamma Experiment David Blyth The NPDGamma experiment measures the parity-violating prompt gamma asymmetry with respect to neutron spin in the capture of polarized cold neutrons on a liquid hydrogen target. The parity-violating prompt gamma directional asymmetry is sensitive to the $\Delta\text{I}=1$ weak potential and is therefore a measure of the strength of the hadronic interaction due to weak pion exchange. Analysis of the data uncovered an issue with the background target composition which led to new direct measurements of the hydrogen vessel material in the first half of 2016. This talk will motivate and describe the new background subtraction strategy and discuss the current status of its implementation. [Preview Abstract] |
Friday, October 14, 2016 11:54AM - 12:06PM |
DG.00006: A measurement of the parity violating asymmetry in the neutron capture on $^3$He at SNS. Latiful Kabir Weak nucleon nucleon couplings are largely unknown because of it's non-perturbative nature which makes the calculations and experiments challenging. However, parity violation (PV) can be used to isolate the weak contributions from the strong part and thus studies of PV in hadronic systems offer a unique probe of nucleon structure. The n-$^3$He experiment at the Spallation Neutron Source at the ORNL measures the parity violating asymmetry of the recoil proton momentum $\vec{k}_p$ with respect to the neutron spin $\vec{\sigma}_n$ in the reaction $\rm n + {}^3He \to p + T + 765\,keV$. This asymmetry is sensitive to the isospin-conserving and isospin-changing ($\Delta$I = 0,1) parts of the Hadronic Weak Interaction, and is expected to be extremely small ($\sim 10^{-7}$). The experiment will determine this PV asymmetry with the statistical sensitivity of the order of $10^{-8}$. Last year we completed the data taking and the data analysis is well advanced. I will describe the experiment and present the preliminary analysis of the PV asymmetry data of the experiment. [Preview Abstract] |
Friday, October 14, 2016 12:06PM - 12:18PM |
DG.00007: Parity-Violating Neutron Spin Rotation in n-$^4$He Murad Sarsour The neutron spin rotation (NSR) collaboration used parity-violating spin rotation of transversely polarized neutrons transmitted through a 0.5 m liquid helium target to constrain weak coupling constants between nucleons. While consistent with theoretical expectation, the upper limit set by this measurement on the rotation angle, d$\phi$/dz = [+1.7 $\pm$ 9.1(stat.) $\pm$1.4(sys.)]$\times 10^{-7}$ rad/m ~\footnote{W. M. Snow et al., PRC \textbf{83}, 022501(R) (2011).}, is limited by statistical uncertainties. The NSR collaboration is preparing a new measurement to improve this statistically-limited result by about an order of magnitude. In addition to using the new high-flux NG-C beam at the National Institute of Standards and Technology (NIST) Center for Neutron Research, the apparatus is being upgraded to take advantage of the larger-area and more divergent NG-C beam. In addition, significant improvements have been made to the cryogenic design and the $^3$He ion chamber. Details of these improvements and readiness of the upgraded apparatus will be discussed and the current theoretical and experimental status of d$\phi$/dz in n-$^{4}$He will be reviewed. [Preview Abstract] |
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