Resummation of singlet structure functions at small x

by Guido ALTARELLI (CERN)

Wednesday 2 Feb 2000, 14:00 → 16:00 Europe/Zurich

TH Auditorium (CERN)

The data at small x collected at HERA show a very good agreement with the QCD evolution equations at two loops. However this agreement is somewhat surprising because neglected terms down by powers of [a ln(1/x) ] could be important. The BFKL approach designed to control these terms, at first sight leads to a very unstable expansion. We propose an improvement of the splitting functions at small x, which overcomes the apparent problems encountered by the BFKL approach. We finally obtain an expansion of the splitting function, which leads to good apparent convergence and to a description of scaling violations valid both at large, and small x.