p–Pb collisions: Particle production and centrality determination in ALICE

Proton–nucleus collisions are an important part of the LHC heavy-ion program for their crucial role in disentangling cold nuclear matter effects from final state effects. Many initial state effects are expected to depend on the number of binary nucleon–nucleon collisions. The centrality determination is needed to provide a geometrical scale to study the underlying collision dynamics. Differently from nucleus–nucleus collisions, where the centrality can be determined by measuring charged particle multiplicity produced at midrapidity, in proton–nucleus collisions the presence of large fluctuations together with the reduced range of particle multiplicity generate a bias which depends on the kinematical range used for the event characterization.