Measurement of the azimuthal anisotropy of charged-particle production in Xe+Xe collisions at sNN=5.44 TeV with the ATLAS detect

Abstract

This paper describes the measurements of flow harmonics v 2-v 6 in 3 μb −1 of Xe + Xe collisions at √ s NN = 5.44 TeV performed using the ATLAS detector at the Large Hadron Collider (LHC). Measurements of the centrality, multiplicity, and p T dependence of the v n obtained using two-particle correlations and the scalar product technique are presented. The measurements are also performed using a template-fit procedure, which was developed to remove nonflow correlations in small collision systems. This nonflow removal is shown to have a significant influence on the measured v n at high p T , especially in peripheral events. Comparisons of the measured v n with measurements in Pb + Pb collisions and p + Pb collisions at √ s NN = 5.02 TeV are also presented. The v n values in Xe + Xe collisions are observed to be larger than those in Pb + Pb collisions for n = 2, 3, and 4 in the most central events. However, with decreasing centrality or increasing harmonic order n, the v n values in Xe + Xe collisions become smaller than those in Pb + Pb collisions. The v n in Xe + Xe and Pb + Pb collisions are also compared as a function of the mean number of participating nucleons, N part , and the measured charged-particle multiplicity in the detector. The v 3 values in Xe + Xe and Pb + Pb collisions are observed to be similar at the same N part or multiplicity, but the other harmonics are significantly different. The ratios of the measured v n in Xe + Xe and Pb + Pb collisions, as a function of centrality, are also compared to theoretical calculations.

Azimuthal anisotropy in Cu+Au collisions at sNN=200 GeV

“…"%$+<& 5,607.&+%0*-8!,+00 00000:0"*';;+&!$,0#"!7,$#"<&* via two-particle correlation (v dipole 1 relative to participant plane) [25,26] taking into account the momentum conservation effect which requires model-dependent treatment. The v dipole 1 measured using two-particle correlation [25] shows ∼40 times larger magnitude than v even 1 measured with spectator planes. This difference can be explained by the weak correlation of cos(Ψ p SP − Ψ 1,3 ) as discussed in Ref.…”

Recent ATLAS measurements of correlations in Pb+Pb and Xe+Xe collisions

“…The flow harmonics n up to n=7 were found to be non-zero [6]. Similar analysis was repeated for Xe+Xe collisions [4]. In this case the data were limited to a single run, thus statistically meaningful results for harmonics 2 to 6 were obtained.…”

“…These observables were among the first analysed in the Au+Au collisions at RHIC [2] and in Pb+Pb collisions at the LHC [3]. Since then much more detailed studies of various aspects of such correlations were performed and most recently results for Xe+Xe collisions were obtained [4].…”

“…Scaling of flow harmonics of higher order by elliptic flow (upper panels) and triangular flow (lower panels) for selected centrality intervals of Xe+Xe collisions at 5.44 TeV[4].…”

Effect of an anisotropic escape mechanism on elliptic flow in relativistic heavy-ion collisions

“…The symbols in Fig. 2 represents experimental results obtained by the ATLAS collaboration [38]. The other parameters for LHC are taken as i (0, 0) = 85 GeV/fm 3 , and τ i = 0.4 fm/c [39].…”