Spectator shadowing as the source of the breaking of NCQ scaling at RHIC-FXT and FAIR energies

Tom Reichert; Iurii Karpenko

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arXiv · 2609.05315

Spectator shadowing as the source of the breaking of NCQ scaling at RHIC-FXT and FAIR energies

Tom Reichert·Iurii Karpenko

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Abstract

The apparent scaling of the elliptic flow of identified hadrons with the number of constituent quarks indicates the presence of quark coalescence, and in turn suggests the presence of a deconfined state in heavy-ion collisions. Recent measurements at RHIC found a breaking of NCQ scaling at low energies and suggested that this marks the onset of partonic collectivity at higher energies. Here, we present a new framework embedding the effect of spectator shadowing into the flow scaling relations. Using a toy model with an idealized quark coalescence source and a ballistic Glauber model for the bypassing spectator, we demonstrate that the observed breaking is an effect of spectator shadowing.

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Tom Reichert, Iurii Karpenko. 2026-09-04. Spectator shadowing as the source of the breaking of NCQ scaling at RHIC-FXT and FAIR energies. https://arxiv.org/abs/2609.05315

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