Bulletin of the American Physical Society
5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 63, Number 12
Tuesday–Saturday, October 23–27, 2018; Waikoloa, Hawaii
Session FG: Compton Scattering and Related Phenomena |
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Chair: William J. Briscoe, George Washington University Room: Hilton King's 3 |
Friday, October 26, 2018 9:00AM - 9:15AM |
FG.00001: Exploratory study of the 180mTa(γ,γ')180Ta reaction with mono-energetic low-energy photon beams at HIγS Werner Tornow, Megha M. Bhike, Sean W Finch, FNU Krishichayan
For the first time the de-excitation cross section of the isomeric-state nuclide 180mTa has been measured with mono-energetic photon beams in the 1.56 MeV to 3.70 MeV energy range. The measurement of this inelastic scattering cross section on nature's rarest isotope was performed at eight energies at the High-Intensity Gamma-Ray Source facility with natural tantalum targets. After irradiation for typically 20 hours with photon fluxes ranging from 0.3 x 107 γ/(cm2×s) to 3.2 x 107 γ/(cm2×s), the 180mTa de-excitation cross section was obtained from the yield of the Kα1 and Kα2 X rays of 180Hf at 55.79 keV and 54.61 keV, respectively, produced after electron capture on the unstable 180Ta ground state. The cross-section values found vary between (1.9 ± 0.9) mb and (4.7 ± 2.4) mb, providing an astonishingly large cross section for the de-excitation of 180mTa. Extensive tests were performed to check on the reliability of the present data. The effect of bremsstrahlung photons of higher energy than the mono-energetic beam was carefully studied and corrected for. |
Friday, October 26, 2018 9:15AM - 9:30AM |
FG.00002: Studying Nucleon Polarizabilities at MAMI & HIGS Evangeline Downie The nucleon polarizabilities are fundamental properties of the nucleon which describe its response to an electromagnetic field. Their extraction, through Compton scattering studies of the nucleon, can be used to test various models of nucleon structure and dynamics. This talk will give a brief overview of the polarizability programs at MAMI, the MAinzer MIkrotron, in Mainz Germany; and HIGS (the High Intensity Gamma Source) at the Triangle Universities Nuclear Laboratory in Durham, NC. We will show sone recent results and demonstrate the complementarity of these two, very different, setups. |
Friday, October 26, 2018 9:30AM - 9:45AM |
FG.00003: Program of Compton Scattering Studies on Light Nuclei at HIGS Gerald Feldman The High Intensity Gamma-Ray Source (HIGS) delivers monoenergetic photon beams with high linear or circular polarization. To exploit the unique capabilities of this facility, we have begun an ambitious program of Compton scattering studies on light (A = 1-16) nuclei. A state-of-the-art unpolarized cryotarget system has been developed at HIGS that can liquefy hydrogen, deuterium and helium. Initial Compton experiments have been performed below 86 MeV with unpolarized photons on protons, deuterons and 4He. Experiments on deuterium will elucidate the neutron EM polarizabilities and provide high precision data for comparison with chiral Effective Field Theory calculations and with recent data from MAX-Lab at Lund. A new approved experiment on 3He will constitute the first Compton data ever taken on a 3He target, providing an alternate means of accessing the neutron polarizabilities in an entrance channel independent of the usual deuteron experiments. In addition, data on 6Li, 12C and 16O have been taken to characterize the Compton cross section over a range of light nuclei. In this talk, an overview of the Compton program at HIGS will be presented, preliminary results of our recent measurements will be shown, and prospects for future experiments and their impact will be discussed. |
Friday, October 26, 2018 9:45AM - 10:00AM |
FG.00004: Compton Scattering and Nucleon Polarizabilities at HI$\gamma$S Xiaqing Li The electromagnetic polarizabilities of the nucleon are fundamental quantities related to nucleon structure. In the past decade, effective field theories have successfully established a bridge between QCD and low-energy description of the nucleon and made predictions for the polarizabilities. Lattice QCD calculations are also eminent on electromagnetic polarizabilities. High precision data are now needed to benchmark these calculations. To this end, the Compton scattering program at the High Intensity $\gamma$-ray Source (HI$\gamma$S) has provided the Compton scattering cross sections on the deuteron at 65 and 85 MeV to extract the neutron polarizabilities. Recently, data have also been collected at HI$\gamma$S to measure the beam asymmetry of linearly polarized Compton scattering on the proton at 84 MeV to extract the proton polarizabilities independently from the Baldin sum rule. In addition, the Compton scattering cross sections on $^4$He were also measured using a circularly polarized photon beam at 84 MeV. In this talk, I will present the details of the experimental method, the analysis and the results of the 84 MeV Compton scattering data on $^4$He. |
Friday, October 26, 2018 10:00AM - 10:15AM |
FG.00005: The Real Compton Scattering Program at MAMI Philippe Martel The A2 collaboration at the Mainz Microtron has undertaken a large program of real Compton scattering experiments in order to study the nucleon polarizabilities. These parameters describe the response of the proton's internal structure to the application of an electromagnetic field. The lower order terms, called the scalar polarizabilities, had been determined by previous experiments but still had undesirably large uncertainties. The higher order terms, called the spin polarizabilities, had only been determined in various linear combinations. To study these, one needs a combination of a linearly or circularly polarized photon beam with unpolarized, longitudinally polarized, or transversely polarized targets, as well as a large acceptance detector system, all of which are available in A2. This talk will present the efforts of this program to extract these fundamental parameters, and discuss what the future entails. |
Friday, October 26, 2018 10:15AM - 10:30AM |
FG.00006: Compton Scattering of Gamma-Ray Vortex Tomoyuki Maruyama, Takehito Hayakawa, Toshitaka Kajino We study Compton scattering of photons described by Laguerre Gaussian (LG) and Hermite Gaussian (HG) wave functions in the framework of relativistic quantum mechanics. Recently, it is expected to observed such vortex photons in astronomical phenomenon. The momentum of scattered photon distributes outside of the reaction plane determined by the incident photon and the scattered electron, and hence the energy of the scattered photon also distributes. In this work we will report methods to identify the gamma-ray vortex using Compton scattering. |
Friday, October 26, 2018 10:30AM - 10:45AM |
FG.00007: Gamma-rays carrying orbital angular momenta produced by non-linear inverse Thomson scattering Yoshitaka Taira, Masahiro Katoh We theoretically show that gamma-rays carrying orbital angular momenta (OAM) are produced by nonlinear inverse Thomson scattering. High energy electrons in intense circularly polarized light field undergo helical trajectories and radiate harmonic photons possessing helical phase structure and carrying OAM. This novel radiation mechanism would be the basis of OAM photon sources in high energy accelerators and, moreover, in various astrophysical environments. We show some numerical examples. Interactions of high energy OAM photons with atoms and nuclei may trigger new phenomena, which would open new research opportunities in nuclear physics, high energy physics and astrophysics. |
Friday, October 26, 2018 10:45AM - 11:00AM |
FG.00008: ABSTRACT WITHDRAWN
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