Hydrodynamics and Energy Correlators

TL;DR

This paper investigates energy-energy correlators in many-body quantum states from heavy-ion collisions, revealing their angular structure across different regimes and proposing their use to probe medium properties.

Contribution

It provides an analytical framework for EEC angular dependence in hydrodynamic models and explores their sensitivity to initial state anisotropies and collective modes.

Findings

Analytical expression for EEC angular dependence in Gubser flow.

Identification of regimes dominated by disconnected and connected contributions.

EEC behavior similar to conformal field theory states at certain angles.

Abstract

We study energy-energy correlators (EECs) in many-body quantum states, focusing on the matter produced in the aftermath of heavy-ion collisions. We analyze the angular structure of EECs in the collinear limit and identify a sequence of dynamical regimes. At the largest angular separations within the small-angle regime, the observable is dominated by disconnected contributions, leading to a classical scaling determined by the collective flow of the medium. We explicitly construct this contribution for hadrons produced from a hydrodynamic medium described by boost-invariant Gubser flow, obtaining the angular dependence of the EEC analytically. We further consider azimuthal perturbations to this flow, illustrating how EECs can be used to probe anisotropies in the initial state. At smaller angular separations, connected contributions become increasingly important. We argue that in this regime the EEC is controlled by collective hydrodynamic modes. The resulting angular behavior is similar to the one identified in the EECs of heavy and large-charge states of conformal field theories. At even smaller angles, this regime is expected to match onto the structure determined by the light-ray operator product expansion, before eventually crossing over to the smallest-angle behavior characteristic of dilute hadronic matter. Altogether, these results provide a unified picture of the angular structure of EECs in many-body QCD states and suggest new observables sensitive to the properties of matter in heavy-ion collisions.