Lattice computations of small-x parton distributions in a model of parton densities in very large nuclei.

Using weak coupling methods McLerran and Venugopalan [1] expressed the parton distributions in large nuclei as correlation functions of a two dimensional Euclidean field theory. The theory has the dimensionful coupling gμ, where μ ∼ A is the valence quark color charge squared per unit area. We use a lattice regularization to investigate these correlation functions both analytically and numerically for the simplified case of SU(2) gauge theory. In weak coupling (gμL << 5), where L is the transverse size of the nucleus, the numerical results agree with the analytic lattice weak coupling results. For g2μL >> 5, no solutions exist at O(a4) where a is the lattice spacing. This suggests an ill-defined infrared behavior for the two dimensional theory. A recent proposal of McLerran et al. [16] for an analytic solution of the classical problem is discussed briefly. On sabbatical leave from the Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. E-mail: [email protected]