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arXiv · 1410.3448

Transverse single-spin asymmetries in $p^\uparrow p \to γX$ from quark-gluon-quark correlations in the proton

K. Kanazawa·Y. Koike·A. Metz·D. Pitonyak
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Abstract

We analyze the transverse single-spin asymmetry in direct photon production from proton-proton collisions, denoted $A_N^γ$, within collinear twist-3 factorization. We provide a calculation of the contribution due to quark-gluon-quark correlations in the unpolarized proton as well as summarize previous studies on those effects in the polarized proton. Both soft-gluon poles and soft-fermion poles are considered. From this complete result we then estimate $A_N^γ$, including error bands due to uncertainties in the non-perturbative inputs, at kinematics relevant for planned measurements of this observable at the Relativistic Heavy Ion Collider. We find $A_N^γ$ can allow for a "clean" extraction of the Qiu-Sterman function, which could lead to a definitive solution to the so-called "sign mismatch" crisis. Since we use the Sivers function extracted from semi-inclusive deep-inelastic scattering to develop our input for the Qiu-Sterman function, this reaction can also make a statement about the process dependence of the Sivers function.

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K. Kanazawa, Y. Koike, A. Metz, D. Pitonyak. 2014-12-23. Transverse single-spin asymmetries in $p^\uparrow p \to γX$ from quark-gluon-quark correlations in the proton. https://doi.org/10.1103/physrevd.91.014013

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