engleski

Transverse single-spin asymmetry and cross section for π0 and η mesons at large Feynman x in p↑+p collisions at √s=200  GeV

Measurements of the differential cross section and the transverse single-spin asymmetry, AN, vs xF for π0 and η mesons are reported for 0.4<xF<0.75 at an average pseudorapidity of 3.68. A data sample of approximately 6.3  pb-1 was analyzed, which was recorded during p↑+p collisions at √s=200  GeV by the STAR experiment at RHIC. The average transverse beam polarization was 56%. The cross section for π0, including the previously unmeasured region of xF>0.55, is consistent with a perturbative QCD prediction, and the η/π0 cross-section ratio agrees with existing midrapidity measurements. For 0.55<xF<0.75, the average AN for η is 0.210±0.056, and that for π0 is 0.081±0.016. The probability that these two asymmetries are equal is ∼3%.

spin; asymmetry; meson; STAR

STAR Collaboration.