Multi-particle cumulants and corresponding Fourier harmonics are measured for azimuthal angle distributions of charged particles in pp collisions at s = 5.02 and 13 TeV and in p + Pb collisions at sNN = 5.02 TeV, and compared to the results obtained for low-multiplicity Pb+Pb collisions at sNN = 2.76 TeV. These measurements aim to assess the collective nature of particle production. The measurements of multi-particle cumulants confirm the evidence for collective phenomena in p + Pb and low-multiplicity Pb+Pb collisions. On the other hand, the pp results for four-particle cumulants do not demonstrate collective behaviour, indicating that they may be biased by contributions from non-flow correlations. A comparison of multi-particle cumulants and derived Fourier harmonics across different collision systems is presented as a function of the charged-particle multiplicity. For a given multiplicity, the measured Fourier harmonics are largest in Pb+Pb, smaller in p + Pb and smallest in pp collisions. The pp results show no dependence on the collision energy, nor on the multiplicity.

Measurement of multi-particle azimuthal correlations in pp, p + Pb and low-multiplicity Pb + Pb 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.;DeMarco, D. A.;Fabbri, L.;Farina, C.;Fischer, A.;Francis, D.;Gabrielli, A.;Gabrielli, A.;Glasman, C.;Iacobucci, G.;Iodice, M.;Rotonda, L. La;Le, B.;Li, C.;Li, S.;Liu, J.;Liu, L.;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.;