Fluctuations of Flow Harmonics in Pb+Pb Collisions at $\sqrt {s_{NN}}=2.76$ TeV from the Glauber Model

Abstract

In the framework of the Glauber model as implemented in GLISSANDO 2, we study the fluctuations of flow harmonics in Pb+Pb collisions at the LHC energy of √ s N N = 2.76 TeV. The model with wounded nucleons and the admixture of binary collisions leads to reasonable agreement for the ellipticity and triangularity fluctuations with the experimental data from the ATLAS, ALICE, and CMS collaborations, verifying the assumption that the initial eccentricity is approximately proportional to the harmonic flow of charged particles. While the agreement, in particular at the level of event-by-event distributions of eccentricities/flow coefficients in not perfect, it leads to a fair (at the level of a few percent for all centralities except the most peripheral collisions) description of the scaled standard deviation and the F measure which involves the four-particle cumulants. We also discuss the case of quadrangular flow. Computer scripts that generate our results from the GLISSANDO 2 simulations are provided.

The fluctuations of quadrangular flow

“…This, in turn, explains why both v 2 {4} 4 and v 3 {4} 4 are positive, even though they originate from different mechanisms: v 2 {4} is driven by the reaction-plane eccentricity [11] while v 3 {4} is driven by non-Gaussian fluctuations of the initial triangularity [12][13][14]. By contrast, simple linear response to the initial anisotropy in the fourth harmonic is unable to explain the observed fluctuations of v 4 [15,16]. In Sec.…”