Geometric scaling in inclusive eA reactions and nonlinear perturbative QCD

Nuclear enhancement of universal dynamics of high parton densities

We show that the enhancement of the saturation scale in large nuclei relative to the proton is significantly influenced by the effects of quantum evolution and the impact parameter dependence of dipole cross sections in high energy QCD. We demonstrate that there is a strong A dependence in diffractive deeply inelastic scattering and discuss its sensitivity to the measurement of the recoil nucleus.

Relating high-energy Lepton-Hadron, proton-nucleus, and nucleus-nucleus collisions through geometric scaling

A characteristic feature of small-x lepton-proton data from HERA is geometric scaling: the fact that in the region of small Bjorken variable x, x less, similar 0.01, all data can be described by a single variable Q(2)/Q(2)(s,p)(x), with all x dependence encoded in the so-called saturation momentum Q(s,p)(x). Here, we observe that the same scaling ansatz accounts for nuclear photoabsorption cross sections and favors the nuclear dependence Q(2)(s,A) proportional, variant A(alpha)Q(2)(s,p), alpha approximately 4/9. We then make the empirical finding that the same A dependence accounts for the centrality evolution of the multiplicities measured in Au+Au collisions at RHIC. It also allows one to parametrize the high-p(t) particle suppression in d+Au collisions at forward rapidities. If these geometric scaling properties have a common dynamical origin, then this A dependence of Q(2)(s,A) should emerge as a consequence of the underlying dynamical model.

Geometric scaling in inclusive charm production

We show that the cross section for inclusive charm production exhibits geometric scaling in a large range of photon virtualities. In the DESY ep collider HERA kinematic domain the saturation momentum Q(2)(sat)(x) stays below the hard scale micro(2)(c)=4m(2)(c), implying charm production probing mostly the color transparency regime and unitarization effects being almost negligible. We derive our results considering two saturation models which are able to describe the HERA data for the proton structure function at small values of the Bjorken variable x. A striking feature is the scaling on tau identical with Q(2)/Q(2)(sat)(x) above te saturation limit, corroborating recent theoretical studies.