Single Transverse Spin Asymmetries of Identified Charged Hadrons in Polarized p+p Collisions at $\sqrt{s}$ = 62.4 GeV

Abstract

The first measurements of $x_F$-dependent single spin asymmetries of identified charged hadrons, $\ddot{I}{€}^{\pm }$, $K^{\pm }$, and protons, from transversely polarized proton-proton collisions at 62.4 GeV at RHIC are presented. The measurements extend to high-$x_F$ ($|x_F|\sim 0.6$) in both the forward and backward directions.Large asymmetries are seen in the pion and kaon channels. The asymmetries in inclusive $\ddot{I}{€}^{+}$ production, $A_N(\ddot{I}{€}^{+})$, increase with $x_F$ from 0 to $\sim$0.25 %at $x_F=0.6$ and $A_N(\ddot{I}{€}^{-})$ decrease from 0 to $\sim$$-$0.4. Even though $K^{-}$ contains no valence quarks, observed asymmetries for $K^{-}$ unexpectedly show positive values similar to those for $K^{+}$, increasing with $x_F$, whereas proton asymmetries are consistent with zero over the measured kinematic range. Comparisons of the data with predictions of QCD-based models are presented. The flavor dependent single spin asymmetry measurements of identified hadrons allow for stringent tests of theoretical models of partonic dynamics in the RHIC energy regime.

4 pages, 5 figures. 36 authors. Published version in PRL