ATLAS Collaboration2018-11-012018-11-012017-06-26Aaboud, M., Aad, G., Abbott, B. et al. Eur. Phys. J. C (2017) 77: 428. https://doi.org/10.1140/epjc/s10052-017-4988-1https://hdl.handle.net/1808/27143Multi-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.© CERN for the benefit of the ATLAS collaboration 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.https://creativecommons.org/licenses/by/4.0/Article10.1140/epjc/s10052-017-4988-1openAccess