Showing papers by "W. Meyer published in 1998"
Tohoku University1, Stanford University2, University of Pennsylvania3, American University4, California Institute of Technology5, University of Virginia6, University of Wisconsin-Madison7, University of Massachusetts Amherst8, University of Mississippi9, University of Michigan10, University of Liverpool11, Lawrence Livermore National Laboratory12, Thomas Jefferson National Accelerator Facility13, University of Bonn14, University of Basel15, Naval Postgraduate School16, College of William & Mary17, Old Dominion University18, Temple University19, Kent State University20, Florida International University21, CERN22
TL;DR: In this paper, the authors reported measurements of the proton and deuteron spin structure functions at beam energies of 29.1, 16.2, and 9.7 GeV.
Abstract: Measurements are reported of the proton and deuteron spin structure functions ${g}_{1}^{p}$ and ${g}_{1}^{d}$ at beam energies of 29.1, 16.2, and 9.7 GeV, and ${g}_{2}^{p}$ and ${g}_{2}^{d}$ at a beam energy of 29.1 GeV. The integrals ${\ensuremath{\Gamma}}_{p}={\ensuremath{\int}}_{0}^{1}{g}_{1}^{p}{(x,Q}^{2})dx$ and ${\ensuremath{\Gamma}}_{d}={\ensuremath{\int}}_{0}^{1}{g}_{1}^{d}{(x,Q}^{2})dx$ were evaluated at fixed ${Q}^{2}=3(\mathrm{GeV}{/c)}^{2}$ using the full data set to yield ${\ensuremath{\Gamma}}_{p}=0.132\ifmmode\pm\else\textpm\fi{}0.003(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.009(\mathrm{syst})$ and ${\ensuremath{\Gamma}}_{d}=0.047\ifmmode\pm\else\textpm\fi{}0.003\ifmmode\pm\else\textpm\fi{}0.006.$ The ${Q}^{2}$ dependence of the ratio ${g}_{1}{/F}_{1}$ was studied and found to be small for ${Q}^{2}g1(\mathrm{GeV}{/c)}^{2}.$ Within experimental precision the ${g}_{2}$ data are well described by the twist-2 contribution, ${g}_{2}^{\mathrm{WW}}.$ Twist-3 matrix elements were extracted and compared to theoretical predictions. The asymmetry ${A}_{2}$ was measured and found to be significantly smaller than the positivity limit $\sqrt{R}$ for both proton and deuteron targets. ${A}_{2}^{p}$ is found to be positive and inconsistent with zero. Measurements of ${g}_{1}$ in the resonance region show strong variations with $x$ and ${Q}^{2},$ consistent with resonant amplitudes extracted from unpolarized data. These data allow us to study the ${Q}^{2}$ dependence of the integrals ${\ensuremath{\Gamma}}_{p}$ and ${\ensuremath{\Gamma}}_{n}$ below the scaling region.
295 citations
TL;DR: In this article, the spin asymmetries A1 and the spin structure functions g1 of the proton and the deuteron in the kinematic range 0.0008
Abstract: We present the final results of the spin asymmetries A1 and the spin structure functions g1 of the proton and the deuteron in the kinematic range 0.0008
250 citations
TL;DR: In this article, a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 0.003 x Q 2 >1 GeV 2 was presented.
130 citations
TL;DR: In this article, the target asymmetry of the reaction γp→pη from threshold to 1150 MeV has been measured at the tagged photon facility PHOENICS at the Bonn accelerator ELSA.
Abstract: At the tagged photon facility PHOENICS at the Bonn accelerator ELSA a measurement of the target asymmetry of the reaction γp→pη from threshold to 1150 MeV has been performed. Simultaneously the reaction γp→pπ0 has been measured in the first resonance region. Results are presented for both reactions. The target asymmetry data are suited to put considerable constraints on the model parameters used for the theoretical description of meson photoproduction.
82 citations
University of Santiago de Compostela1, Istanbul Technical University2, Uppsala University3, Ludwig Maximilian University of Munich4, French Alternative Energies and Atomic Energy Commission5, University of Trieste6, Ruhr University Bochum7, University of Mainz8, University of Virginia9, Delft University of Technology10, University of California, Los Angeles11, Yale University12, University of Bonn13, Fermilab14, Bielefeld University15, Northwestern University16, University of Wisconsin-Madison17, University of Houston18, University of Freiburg19, Stanford University20, Nagoya University21, University of Miyazaki22, Paul Scherrer Institute23, CERN24, University of California, Santa Cruz25, Joint Institute for Nuclear Research26, Aalto University27, Tel Aviv University28, University of Oslo29, Warsaw University of Technology30, University of Mons31
11 Dec 1998-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a line shape for spin-1 systems with large quadrupolar broadening was developed which allowed the nitrogen polarization in the ammonia to be determined with a 10% relative error.
Abstract: The 1996 data taking of the SMC experiment used polarized protons to measure the spin-dependent structure function g(1) of the proton. Three liters of solid granular ammonia were irradiated at the Bonn electron linac in order to create the paramagnetic radicals which are needed for polarizing the protons. Proton polarizations of +/- (90 +/- 2.5)% were routinely reached. An analysis based on a theoretical line shape for spin-1. systems with large quadrupolar broadening was developed which allowed the nitrogen polarization in the ammonia to be determined with a 10% relative error. The measured quadrupolar coupling constant of N-14 agrees well with earlier extrapolated values. The polarization of the nitrogen nuclei was measured as a function of the proton polarization in order to provide a test of the equal spin temperature (EST) hypothesis. It was found to be closely valid under the dynamic nuclear polarization conditions with which the protons are polarized. Large deviations from EST could be induced by cross relaxing the proton and nitrogen spin systems at low fields. Nitrogen polarizations up to 40% were reached by these means. (C) 1998 Elsevier Science B.V. All rights reserved.
17 citations
01 Jan 1998
12 citations
01 Dec 1998-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a superconducting wire is wound on the inner cooling shield of the vertical dilution refrigerator of the Bonn Frozen Spin Target (BoFroST), which is used for a measurement of the target asymmetry in the η-photoproduction γp↑→ηp with the PHOENICS-detector at the BER.
Abstract: A new concept of a small superconducting ‘holding magnet’, placed inside a polarization refrigerator, has been developed for frozen spin targets. The superconducting wire is wound on the inner cooling shield of the vertical dilution refrigerator of the Bonn Frozen Spin Target (BoFroST). The maximum field of the magnet is 0.38 tesla. Based on this concept, the frozen spin target was used for a measurement of the target asymmetry in the η-photoproduction γp↑→ηp with the PHOENICS-detector at the Bonn electron stretcher accelerator ELSA.
5 citations
Journal Article•
3 citations
TL;DR: The first measurement of the target asymmetry for the η-photoproduction reaction γ p → η p at threshol has been performed at the stretcher accelearator ELSA in Bonn.