212 articles – 1955 Notices  [english version]
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Inclusive cross section and single-transverse-spin asymmetry for very forward neutron production in polarized p+p collisions at sqrt(s)=200 GeV
Adare A., Aphecetche L., Hadj Henni A., Atomssa E.T., d'Enterria D. et al
Physical Review D 88 (2012) 032006 - http://hal.in2p3.fr/in2p3-00734009
Physique/Physique des Hautes Energies - Expérience
Physique/Physique Nucléaire Expérimentale
Inclusive cross section and single-transverse-spin asymmetry for very forward neutron production in polarized p+p collisions at sqrt(s)=200 GeV
A. Adare, L. Aphecetche1, A. Hadj Henni1, E.T. Atomssa2, D. d'Enterria2, O. Drapier2, F. Fleuret2, M. Gonin2, R. Granier de Cassagnac2, A. Rakotozafindrabe2, V.-N. Tram2, G. Roche3, P. Rosnet3
1 :  SUBATECH - Laboratoire SUBATECH Nantes
CNRS : UMR6457 – IN2P3 – Université de Nantes – École Nationale Supérieure des Mines - Nantes
4, rue Alfred Kastler - 44070 Nantes Cedex 03
2 :  LLR - Laboratoire Leprince-Ringuet
CNRS : UMR7638 – IN2P3 – Polytechnique - X
Route de Saclay - 91128 Palaiseau Cedex
3 :  LPC - Laboratoire de Physique Corpusculaire [Clermont-Ferrand]
CNRS : UMR6533 – IN2P3 – Université Blaise Pascal - Clermont-Ferrand II
Campus des Cézeaux 24, avenue des Landais BP 80026 63171 Aubière Cedex
The energy dependence of the single-transverse-spin asymmetry, A_N, and the cross section for neutron production at very forward angles were measured in the PHENIX experiment at RHIC for polarized p+p collisions at sqrt(s)=200 GeV. The neutrons were observed in forward detectors covering an angular range of up to 2.2 mrad. We report results for neutrons with momentum fraction of x_F=0.45 to 1.0. The energy dependence of the measured cross sections were consistent with x_F scaling, compared to measurements by an ISR experiment which measured neutron production in unpolarized p+p collisions at sqrt(s)=30.6--62.7 GeV. The cross sections for large x_F neutron production for p+p collisions, as well as those in e+p collisions measured at HERA, are described by a pion exchange mechanism. The observed forward neutron asymmetries were large, reaching A_N=-0.08+/-0.02 for x_F=0.8; the measured backward asymmetries, for negative x_F, were consistent with zero. The observed asymmetry for forward neutron production is discussed within the pion exchange framework, with interference between the spin-flip amplitude due to the pion exchange and nonflip amplitudes from all Reggeon exchanges. Within the pion exchange description, the measured neutron asymmetry is sensitive to the contribution of other Reggeon exchanges even for small amplitudes.

Articles dans des revues avec comité de lecture
Physical Review D (Phys. Rev. D)
Publisher American Physical Society
ISSN 1550-7998 (eISSN : 1550-2368)

see paper for full list of authors - 383 authors, 16 pages, 18 figures, 6 tables. Submitted to Phys. Rev. D. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html
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