Forward-backward multiplicity correlations in pp, p + Pb and Pb + Pb collisions with the ATLAS detector

Two-particle pseudorapidity correlations are measured in s_NN=2.76 TeV Pb+Pb, s_NN=5.02 TeV p+Pb and s=13 TeV pp collisions [ATLAS Collaboration, ATLAS-CONF-2015-051; ATLAS-CONF-2015-020]. Correlation function is measured using charged particles in the pseudorapidity range |η|<2.4 with transverse momentum p_T>0.2 GeV, and it is measured as a function of event multiplicity, defined by number of charged particles with |η|<2.5 and p_T>0.4 GeV. The correlation function is decomposed into a short-range component (SRC) and a long-range component (LRC). The SRC differs significantly between the opposite-charge pairs and same-charge pairs, and between the three collision systems at similar multiplicity. The LRC is described approximately by 1+〈a₁²〉η₁η₂ in all collision systems over the full multiplicity range. The values of 〈a₁²〉 are consistent between the opposite-charge and same-charge pairs, and are similar for the three collision systems at similar multiplicity. The values of 〈a₁²〉 and the magnitude of the SRC both follow a power-law dependence on the event multiplicity.