S. Goertz

First measurement of the Gerasimov-Drell-Hearn integral for Hydrogen from 200 to 800 MeV

A direct measurement of the helicity dependence of the total photoabsorption cross section on the proton was carried out at MAMI (Mainz) in the energy range 200<E_gamma<800 MeV. The experiment used a 4

A new frozen-spin target for 4π particle detection

\pi

Helicity amplitudes A1/2 and A3/2 for the D13(1520) resonance obtained from the gamma-->p-->-->ppi(0) Reaction.

detection system, a circularly polarized tagged photon beam and a frozen spin target. The contributions to the Gerasimov-Drell-Hearn sum rule and to the forward spin polarizability

Polarized H, D and 3He targets for particle physics experiments

\gamma_0

First results of the large COMPASS 6LiD polarized target

determined from the data are 226 \pm 5 (stat)\pm 12(sys) \mu b and -187 \pm 8 (stat)\pm 10(sys)10^{-6} fm^4, respectively, for 200<E_\gamma<800 MeV.

The polarization observables T, P, and H and their impact on gamma p -< p pi(0) multipoles

Abstract A new frozen-spin target has been developed, that allows the detection of emitted particles in an angular acceptance of almost 4π in the laboratory frame. The central part of this new target represents a 3He/4He dilution refrigerator that is installed horizontally along the beam axis. The refrigerator includes an internal superconducting holding coil to maintain the nucleon polarization in the frozen-spin mode longitudinally to the beam. The design of the dilution refrigerator and the use of an internal holding coil enabled for the first time the measurement of a spin-dependent total cross section in combination with a polarized solid state target. This new frozen-spin target was used successfully to measure the helicity asymmetry of the total photoabsorption cross-section at the Mainz accelerator facility MAMI. This experiment has been performed in order to verify for the first time the GDH sum rule.

Polarization measurements of TEMPO-doped butanol targets☆

The helicity dependence of the gamma-->p-->-->ppi(0) reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4pi-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes.

Double-polarization observable G in neutral-pion photoproduction off the proton

Abstract The development, in the early 1960s, of the dynamic nuclear polarization scheme in solid diamagnetic materials, doped with paramagnetic radicals, led to the use of solid polarized H and D targets in numerous nuclear and particle physics experiments. In the 1980s this well established technology was supplemented by the developments of polarized H, D and 3He gas targets, fed by atomic beams or by optically pumped gas. Since then steady progress has been made in all contributing sub-systems so that proton polarization values around 90% and deuteron as well as 3He polarization values between 40% and 85% have been routinely achieved in various setups. These polarization values have been measured with a relative accuracy of ±5% or better using nuclear magnetic resonance techniques and other improved polarimetry methods. Many experiments with reasonably high luminosities have taken advantage of these developments and many more are being planned, especially with electromagnetic probes.

Investigations in high temperature irradiated 6,7LiH and 6LiD, its dynamic nuclear polarization and radiation resistance

The COMPASS (NA58) experiment at CERN operates with a large solid polarized target (PT) to study the spin structure of the nucleon. The COMPASS PT system started its operation with the target material 6 LiD in 2001. Deuteron polarizations of þ54:2% and � 47:1% were achieved in a 3 He= 4 He dilution refrigerator at a magnetic field of 2: 5T : The equal spin temperature (EST) concept was found to hold among the deuteron, the 6 Li and the 7 Li nuclei during the dynamic nuclear polarization (DNP) process. The agreement with the EST concept allows the permanent monitoring of only one nuclear species by the nuclear magnetic resonance (NMR) method. r 2003 Elsevier Science B.V. All rights reserved.

Helicity dependence of the reaction in the second resonance region

Data on the polarization observables T, P, and H for the reaction gamma p -> p pi(0) are reported. Compared to earlier data from other experiments, our data are more precise and extend the covered range in energy and angle substantially. The results were extracted from azimuthal asymmetries measured using a transversely polarized target and linearly polarized photons. The data were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS detector. Within the Bonn-Gatchina partial wave analysis, the new polarization data lead to a significant narrowing of the error band for the multipoles for neutral-pion photoproduction