Bose-Einstein correlations of pion pairs in central Pb+Pb collisions at CERN SPS energies

TL;DR

This study measures Bose-Einstein correlations of pion pairs in central Pb+Pb collisions at CERN SPS energies, revealing radial flow effects and analyzing source properties through Gaussian fits and blast-wave modeling.

Contribution

It provides new experimental data on pion correlations across multiple energies and applies combined modeling to extract source dynamics in heavy-ion collisions.

Findings

Radius parameters decrease with increasing transverse momentum.

No significant dependence on rapidity or beam energy.

Source properties consistent with strong radial flow.

Abstract

Measurements of Bose-Einstein correlations of pion pairs in central Pb+Pb collisions were performed with the NA49 detector at the CERN SPS for beam energies of 20A, 30A, 40A, 80A, and 158A GeV. Correlation functions were measured in the longitudinally co-moving ``out-side-long'' reference frame as a function of rapidity and transverse momentum in the forward hemisphere of the reaction. Radius and correlation strength parameters were obtained from fits of a Gaussian parametrization. The results show a decrease of the radius parameters with increasing transverse momentum characteristic of strong radial flow in the pion source. No striking dependence on pion-pair rapidity or beam energy is observed. Static and dynamic properties of the pion source are obtained from simultaneous fits with a blast-wave model to radius parameters and midrapidity transverse momentum spectra. Predictions of hydrodynamic and microscopic models of Pb+Pb collisions are discussed.