Neutral Pion Cross Section and Spin Asymmetries at Intermediate Pseudorapidity in Polarized Proton Collisions at √s=200  GeV

Authors

L. Adamczyk, AGH University of Science and Technology, Poland
James K. Adkins, University of KentuckyFollow
G. Agakishiev, Joint Institute for Nuclear Research, Russia
M. M. Aggarwal, Panjab University, India
Z. Ahammed, Variable Energy Cyclotron Centre, India
I. Alekseev, Alikhanov Institute for Theoretical and Experimental Physics, Russia
J. Alford, Kent State University
C. D. Anson, Ohio State University
A. Aparin, Joint Institute for Nuclear Research, Russia
D. Arkhipkin, Brookhaven National Laboratory
Renee H. Fatemi, University of KentuckyFollow
Robert G. Fersch, University of KentuckyFollow
Wolfgang Korsch, University of KentuckyFollow
Suvarna Ramachandran, University of KentuckyFollow
G. Webb, University of Kentucky

Abstract

The differential cross section and spin asymmetries for neutral pions produced within the intermediate pseudorapidity range 0.8<ηp_T/c and is found to agree with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry A_LL is measured in the same pseudorapidity range and spans a range of Bjorken-x down to x≈0.01. The measured A_LL is consistent with model predictions for varying degrees of gluon polarization. The parity-violating asymmetry A_L is also measured and found to be consistent with zero. The transverse single-spin asymmetry A_N is measured over a previously unexplored kinematic range in Feynman-x and p_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_N results presented are consistent with a twist-3 model prediction of a small asymmetry over the present kinematic range.

Document Type

Article

Publication Date

1-15-2014

Notes/Citation Information

Published in Physical Review D: Particles, Fields, Gravitation and Cosmology, v. 89, article 012001, p. 1-11.

© 2014 American Physical Society

The copyright holder has granted permission for posting the article here.

Due to the large number of authors involved, only the first 10 and the ones affiliated with the University of Kentucky are listed in the author section above. The authors of this article are collectively known as STAR Collaboration.

Digital Object Identifier (DOI)

http://dx.doi.org/10.1103/PhysRevD.89.012001

Repository Citation

Adamczyk, L.; Adkins, James K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Anson, C. D.; Aparin, A.; Arkhipkin, D.; Fatemi, Renee H.; Fersch, Robert G.; Korsch, Wolfgang; Ramachandran, Suvarna; and Webb, G., "Neutral Pion Cross Section and Spin Asymmetries at Intermediate Pseudorapidity in Polarized Proton Collisions at √s=200  GeV" (2014). Physics and Astronomy Faculty Publications. 130.
https://uknowledge.uky.edu/physastron_facpub/130