J.L. White

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.

Analyzing-power measurements of Coulomb-nuclear interference with the polarized-proton and -antiproton beams at 185 GeV/c

Abstract The analyzing power AN of proton-proton, proton-hydrocarbon, and antiproton-hydrocarbon, scattering in the Coulomb-nuclear interference region has been measured using thhe 185 GeV/c Fermilab polarized-proton and -antiproton beams. The results are found to be consistent with theoretical predictions within statistical uncertainties.

Single‐spin asymmetries and invariant cross sections of the high transverse‐momentum inclusive π0 production in 200 GeV/c pp and p̄p interactions

The π0 inclusive and semi‐inclusive, single‐spin asymmetries have been measured using transversely‐polarized, 200‐GeV/c proton and antiproton beams colliding with an unpolarized hydrogen target. The measured asymmetries are consistent with a value of zero within the error bars for the kinematic regions, −0.15<xF<+0.15 and 1<pT<4.5 GeV/c. These data indicate that the higher‐twist contribution in QCD to the single‐spin asymmetry in inclusive π0 production may not be as large as was previously expected. Additional evidence for such a conclusion comes from the measurement of a semi‐inclusive π0‐charged particle asymmetry, where the associated charged particles are detected opposite to the π0 azimuthal direction. This experiment also has a high‐statistics measurement of the inclusive π0 cross sections for pp and pp collisions at 200 GeV/c.

Measurement of single spin asymmetry for direct photon production in pp collisions at 200 GeV/c

The single spin asymmetry for inclusive direct photon production has been measured using a polarized proton beam of 200 GeV/c with an unpolarized proton target at −0.15<xF<0.15 and 2.5<pT<3.1 GeV/c at Fermilab. The measurement was done using lead glass calorimeters and the photon detectors which surround the fiducial area fo the calorimeters. Background rejection has been done using the surrounding photon detectors. The single spin asymmetry, AN, for the direct photon production is consistent with zero within experimental uncertainty.

Measurements of the proton and deuteron spin structure functionsg1andg2

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.