Measurement of Two-Point Energy Correlators Within Jets in $p$+$p$ Collisions at $\sqrt{s}$ = 200 GeV

TL;DR

This paper presents the first measurement of two-point energy correlators in jets from 200 GeV proton-proton collisions at RHIC, revealing insights into jet substructure and hadronization effects.

Contribution

It introduces the first experimental measurement of the EEC at RHIC, analyzing charge-dependent correlations and comparing results with Monte Carlo models.

Findings

Transition between perturbative and non-perturbative regimes occurs within expected angular scales.

Observed deviations at small angles suggest limitations in current hadronization models.

Results support the universality of the hadronization process across different energies.

Abstract

Hard-scattered partons ejected from high-energy proton-proton collisions undergo parton shower and hadronization, resulting in collimated collections of particles that are clustered into jets. A substructure observable that highlights the transition between the perturbative and non-perturbative regimes of jet evolution in terms of the angle between two particles is the two-point energy correlator (EEC). In this letter, the first measurement of the EEC at RHIC is presented, using data taken from 200 GeV $p$+$p$ collisions by the STAR experiment. The EEC is measured both for all the pairs of particles in jets and separately for pairs with like and opposite electric charges. These measurements demonstrate that the transition between perturbative and non-perturbative effects occurs within an angular region that is consistent with expectations of a universal hadronization regime that scales with jet momentum. Additionally, a deviation from Monte-Carlo predictions at small angles in the charge-selected sample could result from mechanics of hadronization not fully captured by current models.