The sensitivity of RpA to colour recombination effects

Abstract

In hadronization models with colour recombination, partons are allowed to regroup into colour singlet structures that are different from those determined by the perturbative parton shower. This aims at modeling the possibility that soft interactions of partons with the underlying event can change colour connections. If such an effect is at play in proton-proton collisions, it may be expected to be enhanced in proton-nucleus collisions due to the higher colour charge density in the underlying event. Here, we provide a qualitative argument that colour recombination effects could lead to a multiplicity dependent hardening of single inclusive hadron spectra that dies out very weakly (∝1/p⊥) with increasing transverse momentum. We present results of a (conservative) model implementation in the cluster hadronization model of the SHERPA event generator. In this model, we find that colour recombination effects harden indeed the single inclusive hadron spectra without affecting the jet spectra, but that this effect does not depend significantly on underlying event activity. We explain this model feature and we argue why, in general, data on proton-nucleus collisions can help to constrain hadronization models used in proton-proton event generators.