2004/08/25 by B. Jager, S. Kretzer, Jager, B. +5
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #hep-ph
paper · pdf · doi:10.48550/arxiv.hep-ph/0408286
4 pages. To appear in the proceedings of 12th International Workshop on Deep Inelastic Scattering (DIS 2004), Strbske Pleso, Slovakia, 14-18 Apr 2004
arxiv created 2004/08/25 · arxiv updated 2009/12/01
The longitudinally polarized gluon density is probed sensitively in hard collisions of polarized protons under the condition that the dominant dynamics are perturbative and of leading twist origin. First data have recently been presented by Phenix on the double-spin asymmetry ALLpi for pi0 production at moderate transverse momentum p_⊥ ≃ 1 - 4 GeV and central rapidity. By means of a systematic investigation of the relevant degrees of freedom we show that the perturbative QCD framework at leading power in p_⊥ produces an asymmetry that is basically positive definite in this kinematic range, i.e. ALLpi\gtrsim O(-10-3) .