Leading- and higher-twist double-spin asymmetries in proton-proton scattering

Extensive work has been done over the last four decades on the leading-twist (twist-2) double-longitudinal spin asymmetry $A_{LL}$. The main goal of this research has been to understand how the spin of the nucleon can be explained in terms of the partons that compose it. Similarly, the twist-3 longitudinal-transverse double-spin asymmetry $A_{LT}$, like the one studied in inclusive DIS and Drell-Yan, also provides important information on the spin structure of hadrons. This talk will focus on the analysis of $A_{LT}$ for photon, hadron, and jet production from nucleon-nucleon collisions, which gives one access to a complete set of collinear twist-3 functions for a transversely polarized nucleon. Moreover, we will discuss how this observable could give insight into both the $A_{LL}$ and transverse single-spin asymmetry $A_{UT}$ domains.