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Title: Nuclear dependence of the transverse-single-spin asymmetry for forward neutron production in polarized $p+A$ collisions at $$\sqrt{s_{_{NN}}}=200$$ GeV

We report that during 2015 the Relativistic Heavy Ion Collider (RHIC) provided collisions of transversely polarized protons with Au and Al nuclei for the first time, enabling the exploration of transverse-single-spin asymmetries with heavy nuclei. Large single-spin asymmetries in very forward neutron production have been previously observed in transversely polarized p+p collisions at RHIC, and the existing theoretical framework that was successful in describing the single-spin asymmetry in p+p collisions predicts only a moderate atomic-mass-number (A) dependence. In contrast, the asymmetries observed at RHIC in p+A collisions showed a surprisingly strong A dependence in inclusive forward neutron production. The observed asymmetry in p+Al collisions is much smaller, while the asymmetry in p+Au collisions is a factor of three larger in absolute value and of opposite sign. Lastly, the interplay of different neutron production mechanisms is discussed as a possible explanation of the observed A dependence.
Authors:
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Publication Date:
Report Number(s):
BNL-114783-2017-JA
Journal ID: ISSN 0031-9007; PRLTAO
Grant/Contract Number:
SC0012704
Type:
Published Article
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 120; Journal Issue: 2; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Orgs:
PHENIX Collaboration
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
OSTI Identifier:
1416077
Alternate Identifier(s):
OSTI ID: 1413950