Viscosity of the matter created in nucleus-nucleus collisions at the SPS measured via two-pion interferometry

TL;DR

This paper discusses the measurement of the viscosity of matter created in nucleus-nucleus collisions at SPS energies using two-pion interferometry, but was withdrawn due to methodological issues and data interpretation errors.

Contribution

The paper attempted to quantify the viscosity of quark-gluon plasma using interferometry data, highlighting the importance of accurate modeling.

Findings

Initial viscosity estimates were affected by incomplete modeling.

Identification of a mistake in RHIC data interpretation.

Recognition of the need for improved analysis methods.

Abstract

This paper has been withdrawn by the authors because the formula used to fit the pion source radii accounted for only one of the two effects of finite viscosity, and because a mistake in interpreting RHIC data was discovered.