Acoustic scaling of anisotropic flow in shape-engineered events: Implications for extraction of the specific shear viscosity of the quark gluon plasma

It is shown that the acoustic scaling patterns of anisotropic flow for different event shapes at a fixed collision centrality (shape-engineered events), provide robust constraints for the event-by-event fluctuations in the initial-state density distribution from ultrarelativistic heavy ion collisions. The empirical scaling parameters also provide a dual-path method for extracting the specific shear viscosity of the quark-gluon plasma (QGP) produced in these collisions. A calibration of these scaling parameters via detailed viscous hydrodynamical model calculations, gives estimates for the plasma produced in collisions of Au + Au () and Pb + Pb (). The estimates are insensitive to the initial-state geometry models considered.