Energy and system-size dependence of two- and four-particle v2 measurements in heavy-ion collisions at sNN=62.4 and 200 GeV and their implications on flow fluctuations and nonflow

Le résumé fourni par la source

We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants ${v}_{2}$ (${v}_{2}{2}$ and ${v}_{2}{4}$) for Au+Au and Cu+Cu collisions at center-of-mass energies $\sqrt{{s}_{{}_{NN}}}=62.4$ and 200 GeV. The difference between ${v}_{2}{{2}}^{2}$ and ${v}_{2}{{4}}^{2}$ is related to ${v}_{2}$ fluctuations (${\ensuremath{\sigma}}_{{v}_{2}}$) and nonflow $({\ensuremath{\delta}}_{2})$. We present an upper limit to ${\ensuremath{\sigma}}_{{v}_{2}}/{v}_{2}$. Following the assumption that eccentricity fluctuations ${\ensuremath{\sigma}}_{\ensuremath{\varepsilon}}$ dominate ${v}_{2}$ fluctuations $\frac{{\ensuremath{\sigma}}_{{v}_{2}}}{{v}_{2}}\ensuremath{\approx}\frac{{\ensuremath{\sigma}}_{\ensuremath{\varepsilon}}}{\ensuremath{\varepsilon}}$ we deduce the nonflow implied for several models of eccentricity fluctuations that would be required for consistency with ${v}_{2}{2}$ and ${v}_{2}{4}$. We also present results on the ratio of ${v}_{2}$ to eccentricity.

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