Status of Polarized PDFs and Higher Twist after the CLAS and COMPASS Data

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 Q2 CLAS data improve essentially our knowledge of higher twist corrections to the spin structure function g1, while the large Q2 COMPASS dala influence mainly the strange quark and gluon polarizations which slightly decrease. It is shown that the uncertainties in the determination of the polarized parlon 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.