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

Adamczyk, L. and Planinić, Mirko and Poljak, Nikola and Zyzak, M. (STAR Collaboration) (2014) Neutral pion cross section and spin asymmetries at intermediate pseudorapidity in polarized proton collisions at √s=200  GeV. Physical Review D, 89 (1). pp. 12001-11. ISSN 1550-7998

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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<pT<16  GeV/c and is found to agree with a next-to-leading order perturbative QCD calculation. The longitudinal 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.

Item Type: Article
Date: January 2014
Subjects: NATURAL SCIENCES > Physics
Additional Information: Copyright (2014) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 10 Jun 2014 13:19
Last Modified: 10 Jun 2014 13:19
URI: http://digre.pmf.unizg.hr/id/eprint/2234

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