Transverse single-spin asymmetry of forward $η$ mesons in $p^{\uparrow}+ p$ collisions at $\sqrt{s} = 200$ GeV

Utilizing the 2012 transversely polarized proton data from the Relativistic Heavy Ion Collider at Brookhaven National Laboratory, the forward $\eta$-meson transverse single-spin asymmetry ($A_N$) was measured for $p^{\uparrow}+p$ collisions at $\sqrt{s}=200$ GeV as a function of Feynman-x ($x_F$) for $0.2