Neutral pion cross section and spin asymmetries at intermediate pseudorapidity in polarized proton collisions at √s = 200 GeV
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PhysRevD.89.012001.pdf
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Author(s)
Adamczyk, L.
Adkins, J. K.
Agakishiev, G.
Aggarwal, M. M.
Ahammed, Z.
Alekseev, I.
Alford, J.
Anson, C. D.
Aparin, A.
Arkhipkin, D.
Date Issued
January 2014
Journal
Physical Review D
Publisher
American Physical Society
Citation
Adamczyk, L., J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, et al. “Neutral Pion Cross Section and Spin Asymmetries at Intermediate Pseudorapidity in Polarized Proton Collisions at √s = 200 GeV.” Phys. Rev. D 89, no. 1 (January 2014).
Version
Author's final manuscript
Abstract
The differential cross section and spin asymmetries for neutral pions produced within the intermediate pseudorapidity range 0.8 < η < 2.0 in polarized proton-proton collisions at √s = 200 GeV are presented. Neutral pions were detected using the end cap electromagnetic calorimeter in the STAR detector at RHIC. The cross section was measured over a transverse momentum range of 5 < p[subscript T] < 16 GeV/c and is found to agree with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry A[subscript LL] is measured in the same pseudorapidity range and spans a range of Bjorken-x down to x ≈ 0.01. The measured A[subscript LL] is consistent with model predictions for varying degrees of gluon polarization. The parity-violating asymmetry A[subscript L] is also measured and found to be consistent with zero. The transverse single-spin asymmetry A[subscript N] is measured over a previously unexplored kinematic range in Feynman-x and p[subscript T]. Such measurements may aid our understanding of the onset and kinematic dependence of the large asymmetries observed at more forward pseudorapidity (η ≈ 3) and their underlying mechanisms. The A[subscript N] results presented are consistent with a twist-3 model prediction of a small asymmetry over the present kinematic range.
MIT Department
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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DOI of Published Version
https://doi.org/10.1103/PhysRevD.89.012001
