Precision Imaging of the Pion Emission Source in Heavy-Ion Collisions via a Global Rest Frame Analysis

TL;DR

This paper introduces a novel method for imaging pion emission sources in heavy-ion collisions by analyzing correlations directly in the global source rest frame, reducing distortions and improving accuracy over traditional frame-dependent approaches.

Contribution

The paper presents a new correlation analysis technique in the global source rest frame, eliminating kinematic distortions present in conventional methods.

Findings

Significant reduction of non-Gaussian artifacts in source images

Improved agreement with model source functions

Enhanced accuracy in determining source geometry

Abstract

Conventional imaging of pion emission sources, conducted in the center-of-mass frame of individual pion pairs (CMFP), suffers from frame-dependent kinematic distortions that bias the reconstructed source morphology. This method introduces spurious correlations due to the relative boost between the CMFP and the true source rest frame (CMFS), leading to systematic image distortions with a pronounced non-Gaussian tail. We present a transformative approach by performing correlation analysis directly in the global source rest frame (CMFS), the physically meaningful reference frame of the collision fireball. This paradigm shift eliminates kinematic contamination inherent in conventional CMFP-based imaging. The resulting source image shows a dramatic suppression of the non-Gaussian artifact and achieves significantly better agreement with pristine model source functions. Our technique offers a more direct and uncontaminated probe of the intrinsic source geometry, overcoming the limitations of prior methods. It provides a clearer and more accurate determination of the spacetime properties of the nuclear collision fireball, marking a significant advancement in the field.