Journal Article Measurement of multi-particle azimuthal correlations in pp, p + Pb and low-multiplicity Pb + Pb collisions with the ATLAS detector

ATLAS Collaboration  ,  Hara, K.  ,  Kim, S.H.  ,  Okawa, H.  ,  Sato, K.  ,  Ulegawa, F.

77 ( 6 )  , p.428 , 2017-06 , Springer
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.

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