The Long Slow Death of the HBT Puzzle, Proceedings for QM 2009

TL;DR

This paper reviews the resolution of the HBT puzzle at RHIC, highlighting how incorporating pre-equilibrium flow, a stiffer equation of state, and viscosity into models explained previously inconsistent femtoscopic source size measurements.

Contribution

It demonstrates that the HBT puzzle is resolved by considering multiple factors that make RHIC collision evolution more explosive, improving model-data agreement.

Findings

Inclusion of pre-equilibrium flow improves model accuracy.

Stiffer equation of state aligns models with experimental data.

Viscosity effects contribute to resolving the HBT puzzle.

Abstract

At the onset of the RHIC era femtoscopic source sizes inferred from two-particle correlations at RHIC defied description with hydrodynamic models. This failure, which became known as the HBT puzzle, now appears to be solved. The source of the discrepancy appears to be a conspiracy of several factors, each of which contributed to making the evolution of RHIC collisions more explosive. These included pre-equilibrium flow, using a stiffer equation of state and adding viscosity.