Elucidating the event-by-event flow fluctuations in heavy-ion collisions via the event-shape selection technique.

The presence of large event-by-event flow fluctuations in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) provides an opportunity to study a broad class of flow observables. This paper explores the correlations among harmonic flow coefficients vn and their phases Φn, as well as the rapidity fluctuation of vn. The study is carried out using the Pb + Pb events generated by the multiphase transport (AMPT) model with fixed impact parameter. The overall ellipticity or triangularity of events is varied by selecting on the eccentricities εn or the magnitudes of the flow vector qn in a subevent for n=2 and 3, respectively. The responses of the harmonic coefficients, the event-plane correlations, and the rapidity fluctuations to the change in εn and qn are then systematized. Strong positive correlations are observed among all even harmonics ν2, ν4, and ν6 (all increase with q2), between ν2 and ν5 (both increase with q2), and between ν3 and ν5 (both increase with q3), consistent with the effects of nonlinear collective response. In contrast, an anticorrelation is observed between ν2 and ν3 similar to that seen between ε2 and ε3. These correlation patterns are found to be independent of whether selecting on qn or εn, validating the ability of qn in selecting the initial geometry. A forward/backward asymmetry of νn(η) is observed for events selected on qn but not on εn, reflecting dynamical fluctuations exposed by the qn selection. Many event-plane correlators show good agreement between qn and εn selections, suggesting that their variations with qn are controlled by the change of εn in the initial geometry. Hence these correlators may serve as promising observables for disentangling the fluctuations generated in various stages of the evolution of the matter created in heavy ion collisions. [ABSTRACT FROM AUTHOR]