Studying Energy-Energy Correlators in pp Collisions at the LHC with a Jet-Free Event-Topology Method

TL;DR

This paper introduces a jet-free method to measure energy-energy correlators in proton-proton collisions at the LHC, enabling analysis in low transverse momentum regimes and providing insights into QCD dynamics without relying on jet reconstruction.

Contribution

The study develops and validates a novel event-topology approach for EEC measurement that does not depend on jet reconstruction, extending analysis capabilities at the LHC.

Findings

EEC peak position scales with the hard process scale.

Quark and gluon events show distinct EEC patterns.

Heavy flavor triggers reveal dead-cone effects.

Abstract

We present a jet-free approach for measuring energy-energy correlators (EEC) in proton-proton (pp) collisions at the Large Hadron Collider (LHC), employing an event-topology method that does not rely on explicit jet reconstruction. Using the leading charged hadron as a reference axis, the azimuthal plane is divided into Toward and Transverse regions, enabling a robust background subtraction and extending EEC measurements into the low $p_T$ regime where conventional jet-based approaches become unreliable. The method is validated through comparisons with conventional jet reconstruction results. We systematically explore the dependence of the EEC on the leading-particle transverse momentum and parton flavor. The observed scaling between the EEC peak position and the hard scale suggests that this topology-based EEC captures effectively the transition between perturbative and non-perturbative QCD regimes. Distinct differences are found between quark- and gluon-initiated events, reflecting their different color charges and radiation patterns. Extending the analysis to heavy flavor, EECs triggered by leading charm mesons exhibit a suppressed magnitude and a peak shifted toward larger angular separations relative to inclusive charged-particle triggers, providing a direct manifestation of the dead-cone effect. This jet-free EEC framework offers a simple and experimentally robust tool for studying the scale and flavor dependence of the QCD dynamics, with promising applications to proton-nucleus and heavy-ion collisions at the LHC.