Impact of CLAS and COMPASS data on Polarized Parton Densities and Higher Twist

Abstract

We have re-analyzed the world data on inclusive polarized DIS including the very precise CLAS proton and deuteron data, as well as the latest COMPASS data on the asymmetry $A_1^d$, and have studied the impact of these data on polarized parton densities and higher twist effects. We demonstrate that the low $Q^2$ CLAS data improve essentially our knowledge of higher twist corrections to the spin structure function $g_1$, while the large $Q^2$ COMPASS data influence mainly the strange quark density. In our new analysis we find that a negative polarized gluon density, or one that changes sign as a function of x, cannot be ruled out from the present DIS data.

Comments: Version to be published in Phys. Rev. D., minor changes in the text, 2 figures and 2 references added