Abstract
The first measurement of longitudinal decorrelations of harmonic flow amplitudes for in collisions at is obtained using of data with the ATLAS detector at the LHC. The decorrelation signal for and is found to be nearly independent of collision centrality and transverse momentum () requirements on final-state particles, but for a strong centrality and dependence is seen. When compared with the results from collisions at , the longitudinal decorrelation signal in midcentral collisions is found to be larger for , but smaller for . Current hydrodynamic models reproduce the ratios of the measured in collisions to those in collisions but fail to describe the magnitudes and trends of the ratios of longitudinal flow decorrelations between and . The results on the system-size dependence provide new insights and an important lever arm to separate effects of the longitudinal structure of the initial state from other early and late time effects in heavy-ion collisions.
- Received 14 January 2020
- Revised 16 June 2020
- Accepted 12 February 2021
DOI:https://doi.org/10.1103/PhysRevLett.126.122301
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© 2021 CERN, for the ATLAS Collaboration