Low x scattering as a critical phenomenon

We discuss deep inelastic scattering at low x as a critical phenomenon in 2 + 1 spacetime dimensions. QCD (SU(2)) near the light cone becomes a critical theory in the limit of lim x --> 0 with a correlation mass m (x) proportional to x(nu /2). We conjecture that the perturbative dipole wave function of the virtual photon in the region 1/Q < x(perpendicular to) < 1/m obeys correlation scaling, psi proportional to (x(perpendicular to))(-(1+n)) before exponentially decaying for distances larger than the inverse correlation mass. This behavior combined with an x-independent dipole proton cross section gives a longitudinal structure function which shows the dominant features of the experimental data. For SU(3) QCD a similar second order phase transition is possible in the presence of quark zero modes on the light cone. (C) 2001 Elsevier Science B.V. All rights reserved.