Higher-point Energy Correlators: Factorization in the Back-to-Back Limit & Non-perturbative Effects

TL;DR

This paper advances the theoretical understanding of N-point energy correlators by deriving a general factorization theorem, computing a key jet function, analyzing non-perturbative effects, and validating predictions with simulations.

Contribution

It introduces a new parametrization that simplifies the phase space, enabling the derivation of a general factorization theorem for arbitrary N and the analysis of non-perturbative effects for non-integer N.

Findings

Derived the factorization theorem for arbitrary N.

Computed the one-loop jet function for NNLL resummation.

Validated analytic predictions against Pythia simulations.

Abstract

N-point energy correlators are powerful observables for studying strong interactions, with applications ranging from extractions of the strong coupling $\alpha_s$ to probes of jet modification in heavy-ion collisions and determination of the top-quark mass. Their practical use has, however, been limited by the complicated phase space for large N. Using a recently introduced parametrization that simplifies this structure, we study projected N-point correlators in two regimes: factorization in the back-to-back limit and leading non-perturbative effects in the collinear limit. While results in the back-to-back regime were previously limited to the energy-energy correlator, our approach allows us to derive the factorization theorem for arbitrary N. We compute the new ingredient, a one-loop jet function, needed for the next-to-next-to-leading-logarithmic resummation, which enables future $\alpha_s$ extractions with complementary systematics. We further determine the analytic structure of leading non-perturbative power corrections for arbitrary N, including their dependence on the center-of-mass energy Q, the value of N, and the angular scale $x$. We present the first results for non-integer N<1, finding that the classical scaling in $x$ acquires an N-dependent modification, and that a new non-perturbative matrix element $\tilde\Omega^{[N]}$ appears. In a certain approximation, $\tilde\Omega^{[N]}$ can be related to the standard parameter $\Omega_1$ relevant for N>1. Our analytic predictions are tested against the hadronization model in Pythia, finding good agreement. The results presented in this paper demonstrate the significant advancements enabled through our new parametrization of energy correlators.