One-point energy correlator for deep inelastic scattering at small $x$

TL;DR

This paper derives the one-point energy correlator in deep inelastic scattering at small x within the Color Glass Condensate framework, providing a new probe for gluon saturation effects at high energies.

Contribution

It introduces the OPEC as a novel observable that directly probes gluon saturation without fragmentation function dependence in the small-x regime.

Findings

Numerical results show sizable nuclear suppression effects.

OPEC is sensitive to saturation phenomena.

Dependence on nonperturbative inputs is minimized.

Abstract

We derive the expressions for the one-point energy correlator (OPEC) in deep inelastic scattering in the high-energy (small-$x$) limit within the Color Glass Condensate framework. The OPEC is computed as a function of the angle between the energy flow and the target proton or nucleus, enabling a systematic exploration of different momentum scales in the scattering process. Owing to the momentum sum rule, the dependence on fragmentation functions cancels, leaving the dipole amplitude as the only nonperturbative input. As a result, the OPEC provides a clean and direct probe of gluon saturation dynamics at small $x$. We present numerical results for representative kinematic configurations relevant to the future Electron--Ion Collider, demonstrating sizable nuclear suppression effects and highlighting the sensitivity of this observable to saturation phenomena.