K. Krueger

Measurement of single spin asymmetry in η-meson production in p↑p and p̄↑p interactions in the beam fragmentation region at 200 GeV/c

We present experimental results on measuring a single spin asymmetry in η-meson production in the interaction of transversely polarized protons and antiprotons at plab = 200 GeV/c with a proton target in the region 0.2 < xF < 0.7 for p↑p, 0.3 < xF < 0.7 for p↑p and 0.7 < pT < 2.0 GeV/c. A comparison of single spin asymmetries in π- and η-meson production is made.

Measurement of the double-spin asymmetry ALL for inclusive multi-γ pair production with 200 GeV/c polarized proton beam and polarized proton target

The invariant double-differential cross section, E1E2d6 delta/dp(1)3dp(2)3, and the double-spin asymmetry, A(LL), for inclusive multi-gamma pair production in which gamma-rays came from neutral mesons were measured with a 200 GeV/c longitudinally-polarized proton beam and a longitudinally-polarized proton target. Most of the multi-gamma pairs comes from two-jet type events which are sensitive to partonic interaction. The A(LL) values were found to be consistent with zero. The invariant double-differential cross section for inclusive pi0pi0 production was also measured. These measured cross sections are consistent with LUND Monte Carlo simulations. Using the LUND Monte Carlo simulation package with the Carlitz-Kaur model of spin dependent distribution functions of valence quarks, the A(LL) values have been compared with theoretical predictions of gluon polarization, DELTAG/G. The results put restrictions on the size of DELTAG/G in the region of 0.05 less-than-or-similar-to x less-than-or-similar-to 0.35.

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.