Speaker
Description
Ultracentral nucleus–nucleus collisions provide a uniquely stringent test of fluctuating initial conditions: although their average transverse geometry is nearly azimuthally symmetric, measurements reveal an unexpected near degeneracy of elliptic and triangular flow, whereas conventional hydrodynamic calculations generally predict (v_2{2}>v_3{2}). An independent challenge is posed by the non-Gaussian structure of ellipticity fluctuations, encoded in the fourth-order cumulant. We introduce TRENTo-Entanglement, a saturation- and entanglement-motivated framework that establishes a direct connection between the entropy initiating hydrodynamic evolution and the quantum entanglement of small-(x) degrees of freedom in the colliding nuclei. The resulting nonlinear entropy-deposition mechanism modifies not only the hierarchy but also the higher-order statistics of initial-state fluctuations. We show that TRENTo-Entanglement can simultaneously bring elliptic and triangular flow toward their observed near degeneracy and generate the intrinsic fourth-cumulant structure required by the data. These results demonstrate that quantum entanglement can leave experimentally accessible imprints on collective flow and provide a qualitatively new organizing principle for modeling the initial state of high-energy nuclear collisions.
