Neutral pion cross section and spin asymmetries at intermediate pseudorapidity in polarized proton collisions at √s=200 GeV

Scientific paper - Original scientific paper

• Author: L. Adamczyk
• Author: ...
• Author: Mirko Planinić
• Author: ...
• Author: Nikola Poljak
• Author: ...
• Author: M. Zyzak
• Collaboration: STAR Collaboration
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

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<pT<16  GeV/c and is found to agree with a next-to-leading order perturbative QCD calculation. The longitudinal... More double-spin asymmetry ALL is measured in the same pseudorapidity range and spans a range of Bjorken-x down to x≈0.01. The measured ALL is consistent with model predictions for varying degrees of gluon polarization. The parity-violating asymmetry AL is also measured and found to be consistent with zero. The transverse single-spin asymmetry AN is measured over a previously unexplored kinematic range in Feynman-x and pT. 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 AN results presented are consistent with a twist-3 model prediction of a small asymmetry over the present kinematic range. Less

• Keywords (english): pion; spin; STAR
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Physical Review D - Particles, Fields, Gravitation and Cosmology
• Numbering: vol. 89, no. 1, 012001
• p-ISSN: 1550-7998
• e-ISSN: 1550-2368
• DOI: https://doi.org/10.1103/PhysRevD.89.012001
• URN:NBN: urn:nbn:hr:217:940652
• Publication: 2014
• Document URL: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.89.012001
• Type of resource: Text
• Access conditions: Open access
• Public note: Copyright (2014) by the American Physical Society. Received 6 September 2013; published 15 January 2014.
• Created on: 2019-11-29 16:06:00