Geometric scaling at BNL RHIC and CERN LHC

We present a new phenomenological model of the dipole scattering amplitude to demonstrate that the RHIC data for hadron production in d-Au collisions for all available rapidities are compatible with geometric scaling, just like the small-x inclusive deep inelastic scattering data. A detailed comparison with earlier geometric scaling violating models of the dipole scattering amplitude in terms of an anomalous dimension γ is made. In order to establish whether the geometric scaling violations expected from small-x evolution equations are present in the data a much larger range in transverse momentum and rapidity must be probed. Predictions for hadron production in p-Pb and p-p collisions at LHC are given. We point out that the falloff of the transverse momentum distribution at LHC is a sensitive probe of the variation of γ in a region where x is much smaller than at RHIC. In this way, the expectation for the rise of γ from small-x evolution can be tested. © 2008 The American Physical Society.