Running coupling effects for the singlet structure function g1 at small x

The running of the QCD coupling is incorporated into the infrared evolution equations for the flavour structure function g1. The explicit expressions for g1 including the total resummation of the double-logarithmic contributions and accounting for the running coupling are obtained. We predict that asymptotically g1∼x−ΔS, with the intercept ΔS≈0.86, which is a factor of 2 larger than the non-singlet intercept ΔNS. The impact of the initial quark (δq) and gluon (δg) densities on the sign of g1 at x⪡1 is discussed and explicit expressions relating δq and δg are obtained.

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