Next-to-Leading Order QCD Corrections to the Polarized Photoproduction of Heavy Flavors

We present a calculation of the next-to-leading order (O(alpha_s^2 alpha)) QCD corrections to heavy flavor photoproduction with longitudinally polarized beams. We apply our results to study the longitudinal spin asymmetry for the total charm quark production cross section which will be utilized by the forthcoming COMPASS experiment at CERN to obtain first direct information on the polarized gluon density Delta g. We also briefly discuss the main theoretical uncertainties inherent in this calculation. In particular we demonstrate that the factorization scale dependence is considerably reduced in next-to-leading order.Comment: 18 pages, LaTeX, 4 figures, uses epsfig and amssymb style

Next-to-leading Order QCD Corrections to A_TT for Single-Inclusive Hadron Production

We report on a calculation of the next-to-leading order QCD corrections to the partonic cross sections contributing to single-inclusive high-p_T hadron production in collisions of transversely polarized hadrons. We give some predictions for the double spin asymmetry A_TT^\pi for the proposed experiments at RHIC and at the GSI.Comment: Presented at DIS 2005, Madison, Wisconsin, USA, April 27-May 1, 200

Probing the parton densities of polarized photons at a linear e^+e^- collider

The present theoretical status of spin-dependent parton densities Delta f^{\gamma}(x,Q^2) of circularly polarized photons is briefly reviewed. It is then demonstrated that measurements of the deep-inelastic spin asymmetry A_1^{\gamma}\simeq g_1^{\gamma}/F_1^{\gamma} and of di-jet rapidity distributions at a future linear e^+e^- collider appear to be particularly suited for a determination the spin-dependent photonic quark and gluon densities, respectively. Special emphasis is devoted to a comparison of the different sources of polarized photons at a linear collider: the equivalent photon approximation and backscattered laser (Compton) photons. It is shown that backscattered laser photons are highly favorable, even indispensable, for decent measurements of the Delta f^{\gamma}(x,Q^2).Comment: 7 pages, LaTeX, 4 eps figures, uses amssymb, espcrc2 (included), and epsfig styles; Contribution to the Proceedings of the `International Conference on the Structure and Interactions of the Photon (Photon99)' [Nucl. Phys. B (Proc. Suppl.)], Freiburg, Germany, May 199

Unveiling the Proton Spin Decomposition at a Future Electron-Ion Collider

We present a detailed assessment of how well a future Electron-Ion Collider could constrain helicity parton distributions in the nucleon and, therefore, unveil the role of the intrinsic spin of quarks and gluons in the proton's spin budget. Any remaining deficit in this decomposition will provide the best indirect constraint on the contribution due to the total orbital angular momenta of quarks and gluons. Specifically, all our studies are performed in the context of global QCD analyses based on realistic pseudo-data and in the light of the most recent data obtained from polarized proton-proton collisions at BNL-RHIC that have provided evidence for a significant gluon polarization in the accessible, albeit limited range of momentum fractions. We also present projections on what can be achieved on the gluon's helicity distribution by the end of BNL-RHIC operations. All estimates of current and projected uncertainties are performed with the robust Lagrange multiplier technique.Comment: 12 pages, 8 eps figure