Nuclear Dependence of the Transverse Single-Spin Asymmetry in the Production of Charged Hadrons at Forward Rapidity in Polarized p plus p, p plus Al, and p plus Au Collisions at root s(NN)=200 GeV
Morrow, S. I.
We report on the nuclear dependence of transverse single-spin asymmetries (TSSAs) in the production of positively charged hadrons in polarized p(up arrow) + p, p(up arrow) + Al, and p(up arrow) + Au collisions at root s(NN) = 200 GeV. The measurements have been performed at forward rapidity (1.4 < eta < 2.4) over the range of transverse momentum (1.8 < p(T) < 7.0 GeV/c) and Feynman x (0.1 < x(F) < 0.2). We observed positive asymmetries for positively charged hadrons in p(up arrow) + p collisions, and significantly reduced asymmetries in p(up arrow) + A collisions. These results reveal a nuclear dependence of TSSAs for charged-hadron production in a regime where perturbative techniques are applicable. These results provide new opportunities to use p(up arrow) + A collisions as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions and to use TSSAs as a new handle in studying small-system collisions.