Fluctuations of pion elliptic flow, triangular flow, and HBT correlation functions in ultrarelativistic heavy ion collisions

We investigate the fluctuations of pion elliptic flow, triangular flow, and Hanbury-Brown–Twiss (HBT) correlation functions for the hydrodynamic sources with fluctuating initial conditions in the heavy ion collisions of Au–Au at √(sNN)=200 GeV and Pb–Pb at √(sNN)=2.76 TeV. A method based on event-subcollection analysis is used to detect these fluctuations in ultrarelativistic heavy ion collisions. We introduce a granularity length to describe the granular inhomogeneity of the initial sources, and investigate its relationships with the fluctuations of the flow harmonics and HBT correlation functions. Our investigations indicate that the fluctuations of the triangular flow of event subcollections are sensitive to the granularity length of the initial source. This dependence provides a way to investigate the granular inhomogeneity of the initial source through analysing the fluctuations of triangular flow in ultrarelativistic heavy ion collisions. (paper)