Heavy Ion Tea

Constraining the Polarization of the Proton's Glue with the $\eta$ Meson at PHENIX
Joseph Seele (U. Colorado)

Abstract: The division of the proton's spin among its quarks and gluons is a fundamental question in modern nuclear physics. The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) measures asymmetries in polarized proton-proton collisions to garner information about the polarization of the quarks and gluons in the proton. The recent measurement of the double helicity asymmetry in mid-rapidity $\eta$ meson production in polarized proton-proton collisions at $\sqrt{s}=200$GeV will be presented, along with a comparison to theoretical expectations made possible by a recent, first extraction of the $\eta$ fragmentation functions.