A. Rijllart

AN INVESTIGATION OF THE SPIN STRUCTURE OF THE PROTON IN DEEP INELASTIC SCATTERING OF POLARISED MUONS ON POLARISED PROTONS

An investigation of the spin structure of the proton in deep inelastic scattering of polarised muons on polarised protons

Measurements of the Proton and Deuteron Spin Structure Functions g1 and g2

Measurements are reported of the proton and deuteron spin structure functions g1 at beam energies of 29.1, 16.2, and 9.7 GeV and g2 at a beam energy of 29.1 GeV. The integrals of g1 over x have been evaluated at fixed Q**2 = 3 (GeV/c)**2 using the full data set. The Q**2 dependence of the ratio g1/F1 was studied and found to be small for Q**2>1 (GeV/c)**2. Within experimental precision the g2 data are well-described by the Wandzura-Wilczek twist-2 contribution. Twist-3 matrix elements were extracted and compared to theoretical predictions. The asymmetry A2 was measured and found to be significantly smaller than the positivity limit for both proton and deuteron targets. A2 for the proton is found to be positive and inconsistent with zero. Measurements of g1 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 first moments of g1 below the scaling region.

Measurements of the Proton and Deuteron Spin Structure Function g2 and Asymmetry A2

We have measured proton and deuteron virtual photon-nucleon asymmetries A2p and A2d and structure functions g2p and g2d over the range 0.03<x<0.8 and 1.3<Q2<10 (GeV/c)2 by inelastically scattering polarized electrons off polarized ammonia targets. Results for A2 are significantly smaller than the positivity limit sqrt(R) for both targets. Within experimental precision, the g2 data are well-described by the twist-2 contribution g2WW. Twist-3 matrix elements have been extracted and are compared to theorectical predictions.

The polarized target station at GKSS

Abstract In cooperation with CERN, a dynamic polarized nuclear target station was built at GKSS-Research Center on SANS-1, aimed at investigation of biomolecule structure. The target consists of a 20 mmol/min dilution refrigerator, which has a basic temperature of 50 mK, a 2.5 T electromagnet, and a carcinotron which delivers the 4 mm microwave at a power up to 5 W. A NMR-system based on the Liverpool Q -meter and the CERN 68K-STAC fulfills the task of polarization measurement, and especially selective nuclear depolarization.

Measurement of the analysing power and the differential cross section of the pp charge-exchange reaction at LEAR

Abstract As part of a programme to study the spin structure of the p p→ n n channel, we have measured the analysing power A 0 n and the differential cross section at an incident antiproton beam momentum of 704 MeV/ c . The analysing power exhibits a remarkable angular dependence, which is poorly reproduced by the existing potential models.

Asymmetry in p¯p elastic scattering

Abstract Asymmetries A 0 n have been measured at LEAR for s ¯ s elastic scattering for 15 beam momenta from 497 to 1550 MeV/ c .

Measurement of the analyzing power of the charge-exchange reaction in the momentum range 546-875 MeV/c at LEAR

Abstract Results are given for the analysing power of the p p→ n n charge-exchange reaction at four incident beam momenta. The measurement is part of an experimental programme to study the spin structure of this reaction at LEAR. The analyzing power shows strong angular and energy dependence, which at present is not reproduced by the existing meson-exchange potential models.

Measurement of dσ/dΩ and Aon in pp elastic scattering between 497 and 1550 MeV/c

Measurements have been made of the differential cross section and asymmetry Aon for pp elastic scattering at 15 incident momenta between 497 MeV/c and 1550 MeV/c. The angular range where both particles have enough energy to traverse target and setup has been covered. The results are compared with predictions of various NN potential models. None of these models fully explains the present results, although the general trend of the data is predicted correctly.

Measurement of the analysing power of the charge-exchange pp → nn reaction in the momentum range 546–1287 MeV/c at LEAR

Final results of the measurement of the analysing power AOn of the pp → nn reaction are presented. Eight measurements in the range 546–1287 MeV/c incoming p momentum have been performed over the full angular range using a solid polarized proton target and the Low Energy Antiproton Ring (LEAR) at CERN antiproton extracted beams.

First measurement of the depolarization parameter D0n0n of the pp → nn charge-exchange reaction

The depolarization parameter D0n0n in the charge-exchange reaction has been measured for the first time at the CERN Low Energy Antiproton Ring (LEAR) at 875 MeV/c antiproton beam momentum, in the forward hemisphere. The measured values of D0n0n are always smaller than ±0.3, indicating that the two-spin amplitudes dominate the scattering matrix as suggested by the meson exchange potential models