Next-to-leading order QCD corrections to high-p_T pion production in longitudinally polarized pp collisions
B. Jager, A. Schafer, M. Stratmann, W. Vogelsang
TL;DR
This work develops next-to-leading order QCD corrections for single-inclusive high-$p_T$ pion production in longitudinally polarized $pp$ collisions, enabling more precise access to the gluon polarization Δg via the double-spin asymmetry $A_{LL}^{\pi}$ at RHIC. It employs an analytic approach to derive the polarized partonic cross sections, ensures consistency with known unpolarized results, and carefully handles factorization, renormalization, and regularization (notably using the HVBM $\gamma_5$ scheme) to obtain finite hard-scattering pieces. The study explicitly outlines the calculation strategy, combining LO 2→2 processes with NLO real and virtual corrections and performing analytic phase-space integration to yield stable, implementable results for phenomenology. The results provide a robust framework for extracting Δg from RHIC data and underscore the importance of NLO corrections in spin-dependent hadronic processes.
Abstract
We present a calculation for single-inclusive large-p_T pion production in longitudinally polarized pp collisions in next-to-leading order QCD. We choose an approach where fully analytical expressions for the underlying partonic hard-scattering cross sections are obtained. We simultaneously rederive the corresponding corrections to unpolarized scattering and confirm the results existing in the literature. Our results allow to calculate the double-spin asymmetry A_LL^pi for this process at next-to-leading order, which will soon be used at BNL-RHIC to measure the polarization of gluons in the nucleon.