Two-particle pseudorapidity correlations are measured in sNN=2.76TeVPb+Pb, sNN=5.02TeVp+Pb, and s=13TeVpp 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 CN(η1,η2) 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+(a12)1/2η1η2 in all collision systems over the full multiplicity range. The values of (a12)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 (a12)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.

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

Amoroso, S.;Barbero, M.;Bellagamba, L.;Benitez, J.;Bona, M.;Cairo, V. M.;Callea, G.;Cao, T.;Capua, M.;Cardillo, F.;Carli, I.;Cavaliere, V.;Cerri, A.;Chen, H.;Chiarella, V.;Colombo, T.;Conti, G.;Crosetti, G.;David, C.;De Maria, A.;De Pedis, D.;Del Gaudio, M.;Fabbri, L.;Farina, C.;Fischer, A.;Francis, D.;Gabrielli, A.;Gabrielli, A.;Glasman, C.;Iacobucci, G.;Iodice, M.;Jackson, B.;La Rotonda, L.;Le, B.;Li, C.;Li, Q.;Li, S.;Liu, J.;Liu, L.;Liu, M.;Liu, M.;Liu, Y.;Lu, N.;Madaffari, D.;Mancini, G.;Martinez, M.;Mastroberardino, A.;Melo, M.;Meoni, E.;Merola, L.;Perini, L.;Petrucci, F.;Ragusa, F.;Rinaldi, L.;Sanchez, A.;Scarfone, V.;Schioppa, M.;