Gluon-spin contribution to the proton spin from the double-helicity asymmetry in inclusive pi0 production in polarized p+p collisions at [sqrt]s=200 GeV.
Adare A, Afanasiev S, Aidala C, Ajitanand NN, Akiba Y, Al-Bataineh H, Alexander J, Aoki K, Aphecetche L, Asai J, et al. Phys Rev Lett. 2009 Jul 3; 103(1):012003. Epub 2009 Jul 1.