Measurement of forward-backward multiplicity correlations in lead-lead, proton-lead, and proton-proton collisions with the ATLAS detector

摘要

Two-particle pseudorapidity correlations are measured in s_(NN)~(1/2) = 2.76 TeV Pb + Pb, s_(NN)~(1/2) = 5.02 TeV p+Pb, and s~(1/2) = 13 TeV pp collisions at the Large Hadron Collider (LHC), with total integrated luminosities of approximately 7μb~(−1), 28 nb~(−1), and 65 nb~(−1), respectively. The correlation function C_N(η_1,η_2) is measured as a function of event multiplicity using charged particles in the pseudorapidity range |η| < 2.4. The correlation function contains a significant short-range component, which is estimated and subtracted. After removal of the short-range component, the shape of the correlation function is described approximately by 1 + ~(1/2)η_1η_2 in all collision systems over the full multiplicity range. The values of ~(1/2) are consistent for the opposite-charge pairs and same-charge pairs, and for the three collision systems at similar multiplicity. The values of ~(1/2) and the magnitude of the short-range component both follow a power-law dependence on the event multiplicity. The short-range component in p + Pb collisions, after symmetrizing the proton and lead directions, is found to be smaller at a given η than in pp collisions with comparable multiplicity.