Polarized Photoproduction of Heavy Quarks in Next-to-Leading Order

The results of a next-to-leading order calculation of heavy quark production in longitudinally polarized photon-nucleon collisions are presented. At c.m. energy $\sqrt{S}=10$ GeV, for $\vec \gamma +\vec p \to c+X$, cross sections differential in the transverse momentum and rapidity of the charmed quark $c$ and the corresponding asymmetries are presented; also, as functions of $\sqrt{S}$, integrated cross sections, $K$-factors and the corresponding asymmetries are given. Errors in the asymmetries are estimated and the possibility to distinguish between three scerarios differing essentially in the polarized gluon distribution is discussed.Comment: 8 pages, 3 figure

Drell-Yan Non-Singlet Spin Cross Sections and Spin Asymmetry to O(αs2)O(\alpha_s^2) (II)

We present predictions for the non-singlet Drell-Yan longitudinal spin cross sections and spin asymmetry, $A_{LL}$, in proton-proton collisions at large $p_T$ at the RHIC energy of 200\gev at next-to-leading order QCD. The higher order corrections to the non-singlet polarized cross section, $\sigma_{NS}^{LL}$, are sizeable and similar to those found for the unpolarized cross section. The non-singlet asymmetry parameter, $A^{NS}_{LL}$, is very stable against higher order corrections and is a direct measurement of the non-singlet (i.e. valence) polarized quark distributions within the proton.Comment: 24 pages, 13 figure

Approximate Next-to-Leading Order and Next-to-Next-to-Leading Order Corrections

For processes involving structure functions and/or fragmentation functions, arguments that, over a range of a proper kinematic variable, there is a part that dominates the next-to-leading order (NLO) corrections are briefly reviewed. The arguments are tested against more recent NLO and in particular complete next-to-next-to-leading order (NNLO) calculations. A critical examination of when these arguments may not be useful is also presented.Comment: 8 pages and 4 figure

Next-to-Leading Order Corrections to Heavy Flavour Production in Longitudinally Polarized Photon-Nucleon Collisions

A complete next-to-leading order calculation of longitudinally polarized heavy quark photoproduction is presented. All results of the purturbative calculation are given in detail. For reactions and energies of interest cross sections differential in the transverse momentum and rapidity of the heavy quark, total cross sections and the corresponding asymmetries are given. Errors in the asymmetries are estimated and the possibility to distinguish between various scerarios of the polarized gluon distribution is discussed. Our results are compared with other related publications.Comment: 38 pages including 12 postscript figures, late

Partons and QCD in high-energy polarized pp collisions

We present and use a technique for implementing in a fast way, and without any approximations, higher-order calculations of partonic cross sections into global analyses of parton distribution functions. The approach, which is set up in Mellin-moment space, is particularly suited for analyses of future data from polarized proton-proton collisions at RHIC, but not limited to this case. We also briefly discuss the effects of soft-gluon resummations on spin asymmetries.Comment: 6 pages, LaTeX, 5 eps figures, Invited talk presented by W. Vogelsang at the ``International Workshop on the Spin Structure of the Proton and Polarized Collider Physics'', ECT*, Trento, Italy, July 23-28, 200

A Model for the Color Glass Condensate Versus Jet Quenching

A model for the Color Glass Condensate as opposed to jet quenching is proposed for the explanation of the presently available RHIC data. Good fits to these data are presented. A clear way to distinguish between the two possible explanations is also given.Comment: 3 pages, 1 figur

Conatraints on ΔG\Delta G from Prompt Photon plus Jet Production at HERA-N⃗\vec{N}

The utility of prompt photon plus associated jet production for constraining the size and shape of the polarized gluon density of the proton $\Delta G$ is examined at $\sqrt{S}=40$ GeV, appropriate for the proposed HERA-$\vec{N}$ polarized $\vec{p}\vec{p}$ collider experiment. The calculation is performed at next-to-leading order (O($\alpha\alpha_s^2$)) in QCD. The reliability of the predictions are examined in some detail.Comment: 16 pages, 3 figure