Skewness of mean transverse momentum fluctuations in heavy-ion collisions

Abstract : We propose the skewness of mean transverse momentum, pt , fluctuations as a fine probe of hydrodynamic behavior in relativistic nuclear collisions. We describe how the skewness of the pt distribution can be analyzed experimentally, and we use hydrodynamic simulations to predict its value. We predict in particular that pt fluctuations have positive and nontrivial skew at a given collision centrality. We elucidate the origin of this result by deriving generic formulas relating the fluctuations of pt to the fluctuations of the early-time thermodynamic quantities. We thus argue that the positive skewness of pt fluctuations is a universal prediction of hydrodynamic models.