One-, two-, and three-dimensional photon femtoscopy

TL;DR

This paper discusses the potential of photon femtoscopy in high-energy nuclear collisions, emphasizing the importance of choosing appropriate kinematic variables for two-photon correlation functions to improve experimental analysis.

Contribution

It advocates for using the $C( ext{}\Delta E,Q_{ m inv})$ variable over $C(Q_{ m inv})$, enhancing the methodology for photon femtoscopy.

Findings

Preference for $C( ext{ }\Delta E,Q_{ m inv})$ improves correlation analysis.

Photon femtoscopy is now feasible with advanced detectors and electronics.

The paper clarifies optimal kinematic variable choices for future experiments.

Abstract

Femtoscopy with photon pairs is a particularly attractive tool for studying high-energy nuclear collisions. Proposed and extensively discussed in several influential theory articles, it has seen only few applications in experiment because of statistics limitations. With the progress of detectors and electronics, only now it is coming within reach. In this paper we discuss the choice of kinematic variables for two-photon correlation functions. In particular, we argue against $C(Q_{\rm inv})$ and in favor of $C(\Delta E,Q_{\rm inv})$.