Are eccentricity fluctuations able to explain the centrality dependence of v4?

Clément Gombeaud (1) , Jean-Yves Ollitrault (1)

1 IPHT - Institut de Physique Théorique - UMR CNRS 3681

The fourth harmonic of the azimuthal distribution of particles v 4 has been measured for Au-Au collisions at the Relativistic Heavy Ion Collider (RHIC). The centrality dependence of v 4 does not agree with the prediction from hydrodynamics. In particular, the ratio v 4 /(v 2) 2, where v 2 denotes the second harmonic of the azimuthal distribution of particles, is significantly larger than predicted by hydrodynamics. We argue that this discrepancy is mostly due to elliptic flow (v 2) fluctuations. We evaluate these fluctuations on the basis of a Monte Carlo Glauber calculation. The effect of deviations from local thermal equilibrium is also studied, but appears to be only a small correction. Combining these two effects allows us to reproduce experimental data for peripheral and midcentral collisions. However, we are unable to explain the large magnitude of v 4 /(v 2) 2 observed for the most central collisions. Are eccentricity fluctuations able to explain the centrality dependence of v 4 ? 2

Mots clés: Physical Sciences

Clément Gombeaud, Jean-Yves Ollitrault. Are eccentricity fluctuations able to explain the centrality dependence of v4?. Journal of Physics G: Nuclear and Particle Physics, 2010, 37 (9), pp.94024. ⟨10.1088/0954-3899/37/9/094024⟩. ⟨hal-00600843⟩