Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session M12: Electromagnetic Interactions II |
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Sponsoring Units: DNP Chair: Brian Raue, Florida International University Room: Marriott Tampa Waterside Room 11 |
Sunday, April 17, 2005 3:15PM - 3:27PM |
M12.00001: Photodisintegration of a Proton Pair in $^3$He Steffen Strauch Hard photodisintegration of the deuteron has been studied extensively in order to understand the dynamics of the transition from hadronic to quark-gluon descriptions of the strong interaction. Recently Brodsky {\it et al.} [1] have discussed an extension of this program to hard photodisintegration of a proton pair in the $^3$He nucleus. The $\gamma + ^3$He$ \to ppn$ reaction was studied in a comprehensive experiment at Jefferson Lab Hall B for photon energies up to 1.55 GeV [2]. The observed cross section for the photodisintegration of a proton pair in $^3$He is much smaller than for deuteron photodisintegration even at the highest photon energy. Results will be discussed and compared with model calculations. Jefferson Lab experiment E03-101 [3] will be a dedicated experiment to study the photodisintegration of a proton pair in $^3$He for photon energies up to 5 GeV.\\ \hspace{0mm}[1] S.J. Brodsky {\it et al.}, Phys. Lett. B {\bf 578}, 69 (2004)\\ \hspace{0mm}{}[2] S. Niccolai {\it et al.}, Phys. Rev. C {\bf 70}, 064003 (2004)\\ \hspace{0mm}[3] Jefferson Lab Experiment E03-101, R. Gilman and E. Piasetzky (spokespersons) [Preview Abstract] |
Sunday, April 17, 2005 3:27PM - 3:39PM |
M12.00002: Two-Body Photodisintegration of $^4$He into $t+p$ Nawal Benmouna The photodisintegration of $^4$He into $t$ and $p$ is being studied using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Real photons produced with the Hall B bremsstrahlung tagging system in the energy range from 0.35 to 1.55 GeV were incident on a cryogenic liquid $^4$He target. Tritons and protons were detected in coincidence in the CLAS which gives a large angular coverage. Kinematic cuts were applied to select the reaction channel of interest, $^4$He$(\gamma,tp)$. Differential cross sections for this process will be presented. These data will constitute the first investigation of $^4$He photodisintegration into $t+p$ for incident photon energies above 0.4 GeV. [Preview Abstract] |
Sunday, April 17, 2005 3:39PM - 3:51PM |
M12.00003: Photoproduction and Photodisintigration Processes of the Deuteron William Briscoe, Jessica Gohs, Evie Downie, John Annand In 2002 the (SLAC) Crystal Ball multiphoton spectrometer was moved from Brookhaven National Laboratory to Mainz to take advantage of the excellent facilities at MAMI. The combination of TAPS and the Crystal Ball forms a truly 4$\pi $ detection system for protons and neutrons. A photon beam with energies between 400 and 855 MeV has been used with a liquid deuterium target to investigate several photoproduction and photodisintigration processes. Among these are coherent $\pi ^{0}$ production on the deuteron, $\pi ^{0}$ production off the individual quasi-free nucleons, and the photodisintigration of the deuteron into a proton and a neutron. While each of these processes has physics interest, the latter can also be used to calibrate the detection efficiency of the Crystal Ball and TAPS for neutrons. We will report on the preliminary physics and the calibration results from the first measurements made with the deuterium target. [Preview Abstract] |
Sunday, April 17, 2005 3:51PM - 4:03PM |
M12.00004: Coherent pion photoproduction on deuterium at momentum transfer $|t|$ up to 2.2 (GeV/$c$)$^2$} Yordanka Ilieva The reaction $\gamma d \rightarrow \pi^0d$ was measured with the CLAS detector at the Thomas Jefferson National Accelerator Facility at photon energies between 0.54 and 2.0 GeV and pion CM scattering angles between 50$^\circ$ and 150$^\circ$. The total CM energy $s$ varied between 5.5 and 12 GeV$^2$. At pion backward CM angles the scaled invariant cross sections $s^{13}\frac{d\sigma}{dt}$ vary about a constant value as a function of $s$. These variations are most probably due to soft-scattering contributions. Fits to the dependence of $\frac{d\sigma}{dt}$ on $s$ at fixed $\theta^\pi_{CM}$ show that for $\theta^\pi_{CM}>100^\circ$ our data are generally consistent with the predictions of the Constituent Counting Rules (CCR) $[1]$. The predictions of the Reduced Nuclear Amplitudes (RNA) approach $[2]$ are consistent with the data at $-t>1.4$ (GeV/$c$)$^2$ and $s>7$ GeV$^2$. Comparisons with other exclusive processes and traditional meson-nucleon models will be discussed. \vspace{6mm} \newline 1. S.J. Brodsky and G.P. Lepage, Perturbative Quantum Chromodynamics, SLAC-R-224, 133 (1979) \\ 2. S. Brodsky, J.R. Hiller, Chueng-Ryong Ji and G.A. Miller, Phys. Rev. C \textbf{64}, 055204 (2001) [Preview Abstract] |
Sunday, April 17, 2005 4:03PM - 4:15PM |
M12.00005: Studies of the Deuteron at High Four-Momentum Transfer Hassan Ibrahim Experiment E01-020\footnote{Spokespersons: W. Boeglin, M. Jones, A. Klein, P. Ulmer and E. Voutier} systematically explores the $^{2}$H$(e,e'p)n$ reaction (electro-disintegration of the deuteron) over a broad kinematical range of four-momentum transfer, $Q^{2}$ = 0.8, 2.1 and 3.5 $($GeV$/c)^{2}$, and missing momentum, $p_{m}$ = 0.1, 0.2, 0.3, 0.4 and 0.5 GeV$/c$. This systematic approach will help to examine the reaction mechanism and short-distance structure of the deuteron. A separation of the longitudinal-transverse interference response function, $R_{LT} $, at the quasi-elastic peak will provide important constraints for relativistic theories of this reaction. Experiment E01-020 was performed in Hall A at Jefferson Lab in 2002. The physics motivations, run summary and experimental setup will be presented. [Preview Abstract] |
Sunday, April 17, 2005 4:15PM - 4:27PM |
M12.00006: (e,e'p) Studies of the Deuteron at High $Q^2$ Luminita Coman Experiment E01-020 performed in Hall A at Jefferson Laboratory provides a systematic study of the $^2$H(e.e'p)n reaction at large momentum transfers. About 60 kinematic settings were measured, covering the quasifree peak at four momentum transfer $Q^2$ = 0.8, 2.1, and 3.5 (GeV/c$)^2$ and missing momenta of $p_{miss}$ = 0.1, 0.2, 0.3, 0.4, 0.5 GeV/c. The current status of the analysis will be presented and preliminary results for the cross section will be compared to recent theoretical calculations. [Preview Abstract] |
Sunday, April 17, 2005 4:27PM - 4:39PM |
M12.00007: Real Compton Scattering Measurement at Jefferson Lab Areg Danagoulian An experiment has been carried out to measure the cross sections for Real Compton Scattering (RCS) on the proton for 3-6 GeV electron beam energies and a wide distribution of scattering angles. In addition, a measurement of longitudinal and transverse polarization transfers was made at a 3.48 GeV beam energy and a scattering angle of $\theta _{cm}=120^o$. These measurements were done to test the existing theoretical mechanisms for this process and will possibly lead to the determination of RCS form factors which are related to the Generalized Parton Distributions (GPD). The experiment was conducted in Hall A of Thomas Jefferson National Accelerator Facility(Jefferson Lab). It used a polarized and unpolarized electron beam, a $6 \% $ copper radiator (to produce a bremsstrahlung photon beam), the Hall A liquid hydrogen target, a high resolution spectrometer with a focal plane polarimeter, and a photon hodoscope calorimeter built by the RCS collaboration. Results of the cross sections and polarization transfer measurements will be presented. [Preview Abstract] |
Sunday, April 17, 2005 4:39PM - 4:51PM |
M12.00008: Relativistic framework for non-magnetic analysis and design Benjamin Laborde This paper describes a framework for relativistic analysis with effects identical to that of magnetism, but without using magnetism, and uses this framework to design a device which would be difficult or impossible under magnet analysis. With this framework it is possible to analyze electrical systems completely with relativistic electrodynamics, rather than magnetism and electrostatics, with no loss of accuracy, since the two systems are identical. The framework demonstrates the equivalence of magnetism and relativistic electric charge with a mathematical proof using the classical parallel wires experiment. The paper then proceeds to use this result to design an electric propulsion device through relativistic analysis, rather than magnetic analysis. The benefit of this approach is that it liberates us from the magnetic field, and ascribes the forces on a conducting wire to the current in another wire, some distance away, rather than to a magnetic field in the region of the first wire, as in classical analysis. With this new framework we are able to design devices previously unknown in the magnetic domain. The paper describes one such device, the Action Motor, for producing a one-way force, with potential applications in spacecraft propulsion. [Preview Abstract] |
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