Effect of event-by-event fluctuations on hydrodynamical evaluation of elliptical flow

Abstract

Elliptic flow at RHIC is computed event-by-event with NeXSPheRIO. We show that when symmetry of the particle distribution in relation to the reaction plane is assumed, there is a disagreement between the true and reconstructed elliptic flows. We suggest a possible way to take into account the asymmetry and get good agreement between these elliptic flows.

Importance of Granular Structure in the Initial Conditions for the Elliptic Flow

“…2, was also shown in calculations with HIJING [11] and other event generators. As already observed there and studied in [1,2,3,4,5,10], this bumpy structure gives important consequences in the observables. As for the velocity distribution, it gives essentially zero transverse velocity and longitudinal component close to the boost-invariant one.…”

“…Concerning this question, fluctuation in the IC deserves a special consideration. In the past few years, we have studied several effects caused by such fluctuating IC on observables, by using a computational code especially developed for this purpose, which we call NeXSPheRIO [1,2,3,4,5]. In particular, in [1] we have studied the fluctuations of the so called elliptic flow parameter v 2 , showing that they are quite large, which has been confirmed by recent data [6,7].…”

“…As in Ref. [5], we calculated v 2 with respect to the event plane as done experimentally. The event plane has been determined here by all the charged particles (the results with the PHOBOS hit-based method with correction are almost identical).…”

Effects of initial state fluctuations in the final state elliptic flow measurements using the NeXSPheRIO model

“…Furthermore, two or more particle correlations may carry important information on the initial state, hence on the mechanism of QCD dynamics at the very early stage of the collision. Recent studies [13][14][15][16][17][18][19][20][21] show that a scenario including fluctuations of the initial condition in addition to the geometrical eccentricity describes better the experimental data than without the inclusion of initial state fluctuations. These fluctuations in the initial condition will affect the eccentricity by changing the average value and also by introducing an additional fluctuation which will then affect the final observed v 2 values.…”

Summary talk for ISMD 06

“…Grassi presented beautiful results from the SPheRIO model [23]. She showed that fluctuations in the initial conditions can affect the extraction of v2, and argued that this may affect previous extractions.…”