Large P_T P-P collisions to probe the gluonic and sea spin distribution in the proton

Abstract

We parametrise the polarised gluon and sea distribution functions incorporating the interpretation of the EMC experiment that, due to the axial anomaly the observed quark contribution to proton spin Δ Σ' = Δ Σ - f α_s/2π Δ g ≈ 0 at <Q²> =10.7 GeV². Typical processes to isolate the gluonic and sea content of the proton studied here are the large P_T direct photon production processes (a) using single polarized proton PP↑→ γ ↑ ↓ X and (b) polarized beam and target proton P↑ P↑↓→γ X. In both the above process the dominant contribution comes from the "Compton" subprocess and so can be used as a clean probe of the gluonic content of the proton. Large P_T muon pair production P↑ P↑↓→ (μ ⁺μ ^–)X are also studied and we find that the annihilation subprocess dominates, but not much larger than the "Compton" subprocess and so may not be a clean probe of the sea content of the proton. The effect of two loop corrections to the parametrisation and asymmetries are also considered, and are found to be negligible.