Scale dependence and small-χ behaviour of polarized parton distributions Original Research Article

We discuss perturbative evolution of the polarized structure function g1 in the (χ, Q2) plane, with special regard to the small-χ region. We determine g1 in terms of polarized quark and gluon distributions using coefficient functions to order αs. At small χ g1 then displays substantial scale dependence, which necessarily implies a corresponding scale dependence in the large-χ region. This scale dependence has significant consequences for the extraction of the first moment from the experimental data, reducing its value while increasing the error. Conversely, the scale dependence may be used to constrain the size of the polarized gluon distribution.