Christopher Cocuzza, N. T. Hunt-Smith, Wally Melnitchouk, N. Sato, A. W. Thomas
We perform a comprehensive global QCD analysis of spin-dependent parton distribution functions (PDFs), combining all available data on inclusive and semi-inclusive deep-inelastic scattering (DIS), as well as inclusive weak boson and jet production in polarized p p collisions, simultaneously extracting spin-averaged PDFs and fragmentation functions. Including recent Jefferson Lab DIS data at high x , together with subleading power corrections to the leading-twist framework, allows us to verify the stability of the PDFs for W 2 ≥ 4 GeV 2 and quantify the uncertainties on the spin structure functions more reliably. We explore the use of new lattice QCD data on gluonic pseudo-Ioffe time distributions, which, together with jet production and high- x DIS data, improve the constraints on the polarized gluon PDF. The expanded kinematic reach afforded by the data into the high- x region allows us to refine the bounds on higher-twist contributions to the spin structure functions, and test the validity of the Bjorken sum rule.