The PHENIX experiment has studied nuclear effects in p+Al and p+Au collisions at sNN=200GeV on charged hadron production at forward rapidity (1.4<η<2.4, p-going direction) and backward rapidity (−2.2<η<−1.2, A-going direction). Such effects are quantified by measuring nuclear modification factors as a function of transverse momentum and pseudorapidity in various collision multiplicity selections. In central p+Al and p+Au collisions, a suppression (enhancement) is observed at forward (backward) rapidity compared to the binary scaled yields in p+p collisions. The magnitude of enhancement at backward rapidity is larger in p+Au collisions than in p+Al collisions, which have a smaller number of participating nucleons. However, the results at forward rapidity show a similar suppression within uncertainties. The results in the integrated centrality are compared with calculations using nuclear parton distribution functions, which show a reasonable agreement at the forward rapidity but fail to describe the backward rapidity enhancement.

• Received 26 June 2019
• Accepted 24 February 2020

DOI:https://doi.org/10.1103/PhysRevC.101.034910

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Published by the American Physical Society