Progress in the Determination of Polarized PDFs and Higher Twist

TL;DR

This paper analyzes recent precise experimental data to improve understanding of polarized parton densities and higher twist effects, revealing reduced uncertainties and ongoing ambiguities in gluon polarization.

Contribution

It demonstrates how recent CLAS and COMPASS data enhance the determination of polarized PDFs and higher twist corrections, and discusses implications for the proton spin sum rule.

Findings

Low Q^2 CLAS data improve higher twist estimates

Large Q^2 COMPASS data refine strange quark and gluon polarization

Uncertainties in polarized PDFs are significantly reduced

Abstract

The impact of the recent very precise CLAS and COMPASS g1/F1 data on polarized parton densities and higher twist effects is discussed. It is demonstrated that the low Q^2 CLAS data improve essentially our knowledge of higher twist corrections to the spin structure function g1, while the large Q^2 COMPASS data influence mainly the strange quark and gluon polarizations. It is also shown that the uncertainties in the determination of the polarized parton densities are significantly reduced. We find also that the present inclusive DIS data cannot rule out a negative polarized and changing in sign gluon densities. The present status of the proton spin sum rule is discussed.