Speaker
Description
We propose a Generalized Bessel--Power Distribution (GBPD) for the event-by-event initial eccentricity in nucleus--nucleus collisions. In addition to the conventional fluctuation and geometric-anisotropy parameters, the GBPD introduces a radial-shape exponent $k$ that quantifies deviations from the standard quadratic Power form and encodes non-Gaussian eccentricity fluctuations. We show that the conventional distributions impose restrictive relations among higher-order eccentricity moments and cumulants, limiting its applicability in the most central events. By releasing the radial exponent while preserving the physical support $0\leq\varepsilon\leq1$, the GBPD provides a more flexible description of both the eccentricity distribution and its higher-order cumulants. The parametrization fits event-by-event TRENTo simulations for different collision systems and initial-state settings, with emphasis on the physical origin and scaling behavior of the non-Gaussian parameter $k$.
