Correlations, multiplicity distributions, and the ridge in pp and p-Pb collisions

Measurements made by the ALICE Collaboration of single- and two-particle distributions in high-energy pp and p–Pb collisions are used to characterize the interactions in small collision systems, tune models of particle production in QCD, and serve as a baseline for heavy-ion observables. The measurements of charged-particle multiplicity density, 〈dNch / dη〉, and multiplicity distributions are shown in pp and p–Pb collisions, including data from the top center-of-mass energy achieved at the Large Hadron Collider (LHC), √S = 13 TeV. Two-particle angular correlations in p–Pb collisions are studied in detail to investigate long-range correlations in pseudorapidity which are reminiscent of structures previously thought unique to heavy-ion collisions.