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 Q2 sat x stays below the hard scale μ2c 4m2c , 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 t=Q²=Q² sat(x) above te saturation limit, corroborating recent theoretical studies