Breaking of k⊥-factorization for Single Jet Production off Nuclei

The linear k⊥-factorization is part and parcel of the pQCD description of high energy hard processes off free nucleons. In the case of heavy nuclear targets the very concept of nuclear parton density becomes ill-defined as exemplified by the recent derivation [2] of nonlinear nuclear k⊥-factorization for forward dijet production in DIS off nuclei. Here we report a derivation of the related breaking of k⊥-factorization for single-jet processes. We present a general formalism and apply it to several cases of practical interest: open charm and quark & gluon jet production in the central to beam fragmentation region of γ∗p, γ∗A, pp and pA collisions. We show how the pattern of k⊥-factorization breaking and the nature and number of exchanged nuclear pomerons do change within the phase space of produced quark and gluon jets. As an application of the nonlinear k⊥-factorization we discuss the Cronin effect. Our results are also applicable to the p⊥-dependence of the Landau-Pomeranchuk-Migdal effect for, and nuclear quenching of, jets produced in the proton hemisphere of pA collisions.