Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session B7: Physics of Light Systems |
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Sponsoring Units: DNP Room: 201 |
Saturday, April 5, 2014 10:45AM - 10:57AM |
B7.00001: Analysis and Preliminary Results of The NPDGamma Experiment Jason Fry The NPDGamma Experiment measures the parity violating gamma asymmetry from polarized neutrons captured on protons at the Spallation Neutron Source at ORNL. The parity violating asymmetry $A_{\gamma}$ between the neutron spin and the photon momentum is proportional to the $\Delta I = 1$ long range weak meson coupling $h_{\pi}^1$ between nucleons in the hadronic weak interaction. Liquid para-hydrogen production data has been taken since May 2012 and will continue in 2014 to measure $A_{\gamma}$ to a precision of 1$\times$10$^{-8}$. Various aspects of the experiment, preliminary results, and plans to complete NPDGamma in 2014 will be discussed. [Preview Abstract] |
Saturday, April 5, 2014 10:57AM - 11:09AM |
B7.00002: GEANT4 Simulation of the NPDGamma Experiment Emil Frlez The $\vec{n}+p\to d+\gamma$ experiment, currently taking data at the Oak Ridge SNS facility, is a high-precision measurement of weak nuclear forces at low energies. Detecting the correlation between the cold neutron spin and photon direction in the capture of neutrons on Liquid Hydrogen (LH) target, the experiment is sensitive to the properties of neutral weak current. We have written a GEANT4 Monte Carlo simulation of the NPDGamma detector that, in addition to the active CsI detectors, also includes different targets and passive materials as well as the beam line elements. The neutron beam energy spectrum, its profiles, divergencies, and time-of-flight are simulated in detail. We have used the code to cross-calibrate the positions of (i) polarized LH target, (ii) Aluminum target, and (iii) CCl$_4$ target. The responses of the 48 CsI detectors in the simulation were fixed using data taken on the LH target. Both neutron absorption as well as scattering and thermal processes were turned on in the GEANT4 physics lists. We use the results to simulate in detail the data obtained with different targets used in the experiment within a comprehensive analysis. [Preview Abstract] |
Saturday, April 5, 2014 11:09AM - 11:21AM |
B7.00003: $^7_\Lambda$He bound state within three-body approach Vladimir Suslov, Igor Filikhin, Branislav Vlahovic The $^7_\Lambda$He hypernucleus is studied within the cluster model $^5_{\Lambda}\rm He+\rm n+\rm n$, using configuration space Faddeev formalism. Intrinsic structure of the core nucleus is taken into account by the folding procedure applied to construct the $^5_{\Lambda}\rm He-\rm n$ interaction. The OBE simulating potential of the NSC97f model for $\Lambda \rm n$ and phenomenological $\alpha\Lambda$ potential are used. Singlet and triplet components of the folding potential are adjusted to reproduce the $2^-$ excitation energy $E_x$($^6_\Lambda$He) of the $^6_\Lambda$He hypernucleus. A correlation between $E_x$($^6_\Lambda$He) and hyperon binding energy $B_\Lambda$($^7_\Lambda$He) of $^7_\Lambda$He is established. We use this correlation to evaluate $B_\Lambda$($^7_\Lambda$He) taking into account results of our calculation for $E_x$($^6_\Lambda$He) within the three-body model $\alpha+\Lambda+n$. The value obtained for $E_x$($^6_\Lambda$He) is 0.18~MeV. With this value our evaluation for $B_\Lambda$($^7_\Lambda$He) yields 5.69~MeV, which is close to the recently reported experimental data (5.68~MeV). [Preview Abstract] |
Saturday, April 5, 2014 11:21AM - 11:33AM |
B7.00004: ABSTRACT WITHDRAWN |
Saturday, April 5, 2014 11:33AM - 11:45AM |
B7.00005: Two-proton decay from Isobaric Analog States of light nuclei Kyle Brown Recent experiments at the National Superconducting Cyclotron Laboratory at Michigan State University using the charged-particle array HiRA and the gamma-ray array CAESAR have shed light on a new class of two-proton emitters associated with Isobaric Analog States (IAS). The two-proton decay is to the Isobaric Analog state of the daughter, which then gamma decays. These isospin-allowed transitions occur when one-proton decays are forbidden by either energy or isospin conservation, and when two-proton decay to the ground state is isospin forbidden. Three possible examples of this decay path will be discussed ($^{8}$B$_{IAS}$, $^{12}$N$_{IAS}$, and $^{16}$F$_{IAS})$. The known IAS of $^{8}$C in $^{8}$B was confirmed to decay by two-proton emission to the 3.56 MeV IAS in $^{6}$Li. While the IAS in $^{8}$B was previously known, it was measured in this experiment with unbiased statistics and in coincidence with the 3.56 MeV gamma-ray. The IAS in $^{16}$F was investigated for the first time in this experiment and is still under investigation. Previous work on the IAS of $^{12}$O in $^{12}$N at the Cyclotron Institute at Texas A{\&}M will also be presented. [Preview Abstract] |
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