Nonlinear k ⊥ factorization: A new paradigm for hard QCD processes in a nuclear environment

Abstract

A large thickness of the heavy nuclei brings a new hard scale into the pQCD description of hard processes in a nuclear environment. This new scale breaks the conventional linear k⊥ factorization which must be replaced by a new concept of the nonlinear nuclear k⊥ factorization. Here, we review the recent progress in the theory of nonlinear k⊥ factorization. Our focus is on the role of diffractive interactions, the variation of the pattern of k⊥ factorization for single-jet processes from deep inelastic scattering to hadron-nucleus collisions and universality classes for dijet production off nuclei.