Elliptic flow fluctuations in central collisions of spherical and deformed nuclei

Elliptic flow (v2) fluctuations in central heavy-ion collisions are direct probes of the fluctuating geometry of the quark-gluon plasma and, as such, are strongly sensitive to any deviation from spherical symmetry in the shape of the colliding nuclei. I investigate the consequences of nuclear deformation for v2 fluctuations, and I assess whether current models of medium geometry are able to predict and capture such effects. Assuming linear hydrodynamic response between v2 and the eccentricity of the medium, ɛ2, I perform accurate comparisons between model calculations of ɛ2 fluctuations and STAR data on cumulants of elliptic flow in central Au+Au and U+U collisions. From these comparisons, I evince that the most distinct signatures of nuclear deformation appear in the non-Gaussianities of v2 fluctuation, and I show, in particular, that the non-Gaussian v2 fluctuations currently observed in central Au+Au collisions are incompatible with model calculations that implement a quadrupole coefficient of order 12% in the Au197 nuclei. Finally, I make robust predictions for the behavior of higher order cumulants of v2 in collisions of nonspherical nuclei.

Note:

11 pages; 4 figures; v2: overall minor improvements, corrected mistakes in legends of Figs 2 and 4, corrected wrong statement at the beginning of the Conclusions; v3: published version, legend corrected in fig. 3(b)

Relativistic Nuclear Collisions
nucleus: deformation
elliptic flow: fluctuation
geometry: fluctuation
quark gluon: plasma
heavy ion: scattering
symmetry: rotation
non-Gaussianity
impact parameter
hydrodynamics

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Figures(4)

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