Observation of Entanglement Enabled Spin-Interference in the Drell-Söding Process in Au+Au Ultraperipheral Collisions at RHIC

Fuente: arXiv
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Main Author: The STAR Collaboration
Format: Preprint
Published: 2026
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author The STAR Collaboration
author_facet The STAR Collaboration
contents We report a measurement of the Drell-Söding $π^+ π^-$ production in Au + Au ultraperipheral collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}} = 200~\mathrm{GeV}$ using the STAR detector. For the first time, the Entanglement Enabled Spin-Interference (EESI) effect is observed in the Drell-Söding process through the amplitude $A_{2Δϕ}$ of the $\cos(2Δϕ)$ modulation. The measured $A_{2Δϕ}$ exhibits no significant dependence on the invariant mass $M_{π^+ π^-}$. An enhancement of three standard deviations is observed for the Drell-Söding process compared to $ρ^0$ photoproduction. Furthermore, we measure the $|t|$-dependence of the Drell-Söding process and $ρ^0$ photoproduction. The Drell-Söding spectrum falls more steeply with $|t|$ and exhibits diffractive structures shifted to lower $|t|$ compared to $ρ^0$ photoproduction, features that are not captured by theoretical calculations. These results provide new insights into the interplay between quantum interference and photon-nuclear interactions in ultra-peripheral heavy-ion collisions.
format Preprint
id arxiv_https___arxiv_org_abs_2605_23615
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Observation of Entanglement Enabled Spin-Interference in the Drell-Söding Process in Au+Au Ultraperipheral Collisions at RHIC
The STAR Collaboration
Nuclear Experiment
Nuclear Theory
We report a measurement of the Drell-Söding $π^+ π^-$ production in Au + Au ultraperipheral collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}} = 200~\mathrm{GeV}$ using the STAR detector. For the first time, the Entanglement Enabled Spin-Interference (EESI) effect is observed in the Drell-Söding process through the amplitude $A_{2Δϕ}$ of the $\cos(2Δϕ)$ modulation. The measured $A_{2Δϕ}$ exhibits no significant dependence on the invariant mass $M_{π^+ π^-}$. An enhancement of three standard deviations is observed for the Drell-Söding process compared to $ρ^0$ photoproduction. Furthermore, we measure the $|t|$-dependence of the Drell-Söding process and $ρ^0$ photoproduction. The Drell-Söding spectrum falls more steeply with $|t|$ and exhibits diffractive structures shifted to lower $|t|$ compared to $ρ^0$ photoproduction, features that are not captured by theoretical calculations. These results provide new insights into the interplay between quantum interference and photon-nuclear interactions in ultra-peripheral heavy-ion collisions.
title Observation of Entanglement Enabled Spin-Interference in the Drell-Söding Process in Au+Au Ultraperipheral Collisions at RHIC
topic Nuclear Experiment
Nuclear Theory
url https://arxiv.org/abs/2605.23615