English

A compendium of cold-nuclear matter baseline predictions in light-ion collisions

High Energy Physics - Phenomenology 2026-03-04 v2 Nuclear Experiment Nuclear Theory

Abstract

The recent light-ion collision programme at RHIC and the LHC provides a unique opportunity to investigate the onset of quark-gluon plasma formation and parton energy loss in small systems. A quantitative interpretation of emerging jet quenching measurements requires precise control over cold nuclear matter (CNM) effects, which modify hard-process cross sections independently of any hot-medium dynamics. In this work, we present a comprehensive set of perturbative QCD baseline calculations for nuclear modification factors (RAAR_{AA}) in proton-oxygen (pO), oxygen-oxygen (OO) and neon-neon (NeNe) collisions at LHC energies. The study includes charged hadron, neutral pion, prompt photon, and electroweak-boson production computed at next-to-leading order using a broad set of recent nuclear parton distribution functions (nPDFs). We demonstrate that CNM effects alone can induce sizeable suppressions in light-ion systems, with large associated nPDF uncertainties that currently limit the quantitative extraction of parton energy loss. To address this limitation, we explore a range of multi-cross-section ratios in which CNM effects and their uncertainties largely cancel. In particular, ratios of neutral pion ROOR_{OO} to prompt photon ROOR_{OO} or charged hadron ROOR_{OO} to RpO2R_{pO}^2 provide theoretically robust observables with substantially reduced nPDF uncertainties, thereby enhancing sensitivity to possible energy-loss signatures.

Keywords

Cite

@article{arxiv.2602.15928,
  title  = {A compendium of cold-nuclear matter baseline predictions in light-ion collisions},
  author = {Florian Jonas and Constantin Loizides and Aleksas Mazeliauskas and Petja Paakkinen and Nicolas Strangmann},
  journal= {arXiv preprint arXiv:2602.15928},
  year   = {2026}
}

Comments

24 pages, 16 figures, corrected Fig 11(right) and Fig 13(right), updated the text, version submitted to journal, data available at https://github.com/fjonasALICE/pQCDLightIon