Measurement of longitudinal flow correlations in Pb+Pb collisions at √{sNN} = 2.76and 5.02TeV with the ATLAS detector

Measurements of longitudinal flow correlations are presented for charged particles in the pseudorapidity range | η | < 2.4 by using a reference detector at 3.2 <η_ref < 4.8 in Pb+Pb collisions at √{s_NN} = 2.76and 5.02TeV, respectively, with the ATLAS detector at the LHC. It is found that the correlation between the harmonic flow coefficients v_n measured in two separated η intervals does not factorize into the product of single-particle flow harmonic v_n. This breaking of factorization, or flow decorrelation, increases linearly with the η separation between the intervals. The linear coefficients of the flow decorrelation are found to be larger at 2.76 TeV than 5.02 TeV. The longitudinal flow correlations are also measured between v_n of different order in n. The longitudinal fluctuations of v₄ are found to contain significant contribution from the non-linear component from v₂² .