title: Evidence for polarization of gluons in the proton.
abstract: We discuss the impact of recent high-statistics Relativistic Heavy Ion Collider data on the determination of the gluon polarization in the proton in the context of a global QCD analysis of polarized parton distributions. We find evidence for a nonvanishing polarization of gluons in the region of momentum fraction and at the scales mostly probed by the data. Although information from low momentum fractions is presently lacking, this finding is suggestive of a significant contribution of gluon spin to the proton spin, thereby limiting the amount of orbital angular momentum required to balance the proton spin budget.
authors.affiliation: Departamento de Física and IFIBA, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 1 (1428) Buenos Aires, Argentina.
authors.forename: Daniel
authors.initials: D
authors.lastname: de Florian
authors.affiliation: Departamento de Física and IFIBA, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 1 (1428) Buenos Aires, Argentina.
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Sassot
authors.affiliation: Institute for Theoretical Physics, Tübingen University, Auf der Morgenstelle 14, 72076 Tübingen, Germany and Physics Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Stratmann
authors.affiliation: Institute for Theoretical Physics, Tübingen University, Auf der Morgenstelle 14, 72076 Tübingen, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Vogelsang