Observation of flow angle and flow magnitude fluctuations in Pb-Pb collisions at √sNN=5.02 TeV at the CERN Large Hadron Collider

This Letter reports on the first measurements of transverse momentum dependent flow angle psi(n) and flow magnitude upsilon(n) fluctuations determined using new four-particle correlators. The measurements are performed for various centralities in Pb-Pb collisions at a center-of-mass energy per nucleon pair of root s(NN) = 5.02 TeV with ALICE at the CERN Large Hadron Collider. Both flow angle and flow magnitude fluctuations are observed in the presented centrality ranges and are strongest in the most central collisions and for a transverse momentum p(T) > 2 GeV/c. Comparison with theoretical models, including iEBE-VISHNU, MUSIC, and AMPT, show that the measurements exhibit unique sensitivities to the initial state of heavy-ion collisions.

Automated summary

This Letter presents the first measurements of transverse momentum dependent flow angle psi(n) and flow magnitude upsilon(n) fluctuations using new four-particle correlators. The measurements were performed for different centralities in Pb-Pb collisions at a center-of-mass energy per nucleon pair of root s(NN) = 5.02 TeV at the CERN Large Hadron Collider. The results show that both flow angle and flow magnitude fluctuations are observed and have the strongest effect in the most central collisions and for transverse momentum p(T) > 2 GeV/c. Comparison with theoretical models demonstrates the unique sensitivity of these measurements to the initial state of heavy-ion collisions.