Evidence for polarization of gluons in the proton

DANIEL DE FLORIAN; RODOLFO SASSOT; MARCO STRATMANN; WERNER VOGELSANG

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Lugar: New York; Año: 2014 vol. 113 p. 12001 - 12004

0031-9007

We discuss the impact of recent high-statistics RHIC data on the determination of the gluon polarization in the proton in the context of a global analysis of polarized parton distributions. We find clear evidence for a non-vanishing 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.