Measurement of longitudinal flow decorrelations in Pb+Pb collisions at sNN−−−√=2.76and 5.02 TeV with the ATLAS detector
Aaboud, Morad; Aad, Georges; Abbott, Brad; Abdinov, Ovsat Bahram oglu; Abeloos, Baptiste; Abidi, Syed Haider; AbouZeid, Hass; Abraham, Nadine L.; Abramowicz, Halina; Abreu, Henso; Buanes, Trygve; Dale, Ørjan; Eigen, Gerald; Liebig, Wolfgang; Lipniacka, Anna; Martin dit Latour, Bertrand; Mæland, Steffen; Stugu, Bjarne; Yang, Zongchang; Zalieckas, Justas; Bugge, Magnar Kopangen; Cameron, David Gordon; Catmore, James Richard; Feigl, Simon; Franconi, Laura; Garonne, Vincent; Gjelsten, Børge Kile; Gramstad, Eirik; Morisbak, Vanja; Oppen, Henrik; Ould-Saada, Farid; Raddum, Silje Hattrem; Read, Alexander Lincoln; Røhne, Ole Myren; Sandaker, Heidi; Serfon, Cédric; Stapnes, Steinar; Vadla, Knut Oddvar Høie; Abreu, Rômulo F.; Abulaiti, Yiming; Acharya, Bobby S.; Adachi, Shunsuke; Adamczyk, Leszek; Adelman, Jareed; Adersberger, Michael; Adye, Tim; Affolder, Anthony Allen; Afik, Yoav; Agatonovic-Jovin, Tatjana; Agheorghiesei, Catalin; ATLAS, Collaboration
Peer reviewed, Journal article
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Measurements of longitudinal flow correlations are presented for charged particles in the pseudorapidity range |𝜂|<2.4 using 7 and 470 μb−1 of Pb+Pb collisions at 𝑠NN‾‾‾‾√=2.76 and 5.02 TeV, respectively, recorded by the ATLAS detector at the LHC. It is found that the correlation between the harmonic flow coefficients 𝑣𝑛 measured in two separated 𝜂 intervals does not factorise into the product of single-particle coefficients, and this breaking of factorisation, or flow decorrelation, increases linearly with the 𝜂 separation between the intervals. The flow decorrelation is stronger at 2.76 TeV than at 5.02 TeV. Higher-order moments of the correlations are also measured, and the corresponding linear coefficients for the 𝑘th -moment of the 𝑣𝑛 are found to be proportional to k for 𝑣3 , but not for 𝑣2 . The decorrelation effect is separated into contributions from the magnitude of 𝑣𝑛 and the event-plane orientation, each as a function of 𝜂 . These two contributions are found to be comparable. The longitudinal flow correlations are also measured between 𝑣𝑛 of different order in n. The decorrelations of 𝑣2 and 𝑣3 are found to be independent of each other, while the decorrelations of 𝑣4 and 𝑣5 are found to be driven by the nonlinear contribution from 𝑣22 and 𝑣2𝑣3 , respectively.