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Giving wake to energy-energy correlators: Hydrodynamic response on the celestial sphere

João Barata1,*, Matvey V. Kuzmin2,†, José Guilherme Milhano3,4,‡, and Andrey V. Sadofyev3,§

  • 1CERN, Theoretical Physics Department, CH-1211 Geneva 23, Switzerland
  • 2Physics Department, Lomonosov Moscow State University, 1-2 Leninskie Gory, Moscow 119991, Russia
  • 3LIP, Avenida Professor Gama Pinto, 2, P-1649-003 Lisboa, Portugal
  • 4Departmento de Fisica, Instituto Superior Tecnico (IST), Universidade de Lisboa, Avenida Rovisco Pais 1, P-1049-001 Lisboa, Portugal

  • *Contact author: joao.lourenco.henriques.barata@cern.ch
  • †Contact author: kuzmin.mv19@physics.msu.ru
  • ‡Contact author: gmilhano@lip.pt
  • §Contact author: sadofyev@lip.pt
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Phys. Rev. D 112, 016005 – Published 7 July, 2025

DOI: https://doi.org/10.1103/q8pr-djlw

Abstract

The observation of the medium response generated by the propagation of high energy partons in the quark gluon plasma produced in heavy-ion collisions would provide clear and unmistakable evidence for the hydrodynamic behavior of the bulk. Recently, it has been argued that the features of the medium’s backreaction to the jet could be cleanly imprinted in the correlations of asymptotic energy flows, in principle, allowing one to isolate this signal from other uncorrelated physical processes. Nonetheless, the current limited theoretical understanding of these jet observables in heavy-ion collisions constrains their applicability as probes of the medium (hydro)dynamics. In this work, we provide an analytic picture for the medium backreaction’s effect on the energy flux and two point energy correlator. We show that the medium response leads to the emergence of a universal classical scaling law, competing with the perturbative QCD contribution at large angles. Comparing the associated correlator to recent experimental measurements, we find that the observed large angle features can be qualitatively described by a purely hydrodynamically driven response and its interplay with the hard jet component.

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Phys. Rev. D 112, 016005– Published 7 July, 2025
  • Received 11 January 2025
  • Accepted 30 May 2025
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