Energy Correlators Within Jets in Transversely Polarized Proton-Proton Collisions at $\sqrt{s} = 200$ GeV

TL;DR

This paper presents the first measurement of energy correlators within jets in transversely polarized proton-proton collisions, revealing spin-dependent asymmetries that probe nucleon structure and nonperturbative dynamics.

Contribution

It introduces energy correlators as a new tool to study nucleon transversity and nonperturbative effects in polarized collisions at RHIC.

Findings

Observed sizable spin-dependent asymmetries for pion pairs.

Provided sensitivity to nucleon transversity through Mellin moments.

Established energy correlators as a novel probe for nucleon structure.

Abstract

We report the first measurement of one- and two-point energy correlators within jets in transversely polarized proton-proton collisions at $\sqrt{s}=200$ GeV, using the STAR detector at RHIC. These observables quantify the energy-weighted angular distribution of single hadrons and hadron pairs within jets, respectively. Sizable spin-dependent asymmetries are observed for $\pi^+$, $\pi^-$, and $\pi^+\pi^-$ pairs, revealing the onset of nonperturbative dynamics at specific angular scales. By projecting the fragmentation dynamics onto Mellin moments, these measurements provide sensitivity to the nucleon's transversity while minimizing uncertainties from nonperturbative fragmentation functions. These results establish energy correlators as a novel and precise probe of nucleon structure and open a promising avenue for three-dimensional nucleon tomography at the future Electron-Ion Collider.