# Nuclear Dependence of the Transverse-Single-Spin Asymmetry for Forward Neutron Production in Polarized $p+A$ Collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$

Abstract : 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 3 larger in absolute value and of opposite sign. The interplay of different neutron production mechanisms is discussed as a possible explanation of the observed A dependence.
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https://hal.archives-ouvertes.fr/hal-01703767
Contributor : Inspire Hep <>
Submitted on : Thursday, February 8, 2018 - 4:22:02 AM
Last modification on : Wednesday, June 12, 2019 - 7:08:22 PM

### Citation

C. Aidala, Y. Akiba, M. Alfred, V. Andrieux, K. Aoki, et al.. Nuclear Dependence of the Transverse-Single-Spin Asymmetry for Forward Neutron Production in Polarized $p+A$ Collisions at $\sqrt{{s}_{NN}}=200\text{ }\text{ }\mathrm{GeV}$. Phys.Rev.Lett., 2018, 120 (2), pp.022001. ⟨10.1103/PhysRevLett.120.022001⟩. ⟨hal-01703767⟩

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