Anomalous soft photons: status and perspectives

TL;DR

This paper reviews the soft-photon puzzle, exploring the discrepancy between experimental data and theoretical predictions, and discusses future experimental prospects with the ALICE 3 detector at the LHC.

Contribution

It provides a comprehensive overview of the anomalous soft photon production issue and discusses how upcoming experiments can address this longstanding puzzle.

Findings

Summary of the soft-photon puzzle and current theoretical understanding

Discussion of low-mass dileptons as probes of medium properties

Potential of ALICE 3 detector to investigate soft photon anomalies

Abstract

This report summarizes the work of the EMMI Rapid Reaction Task Force on "Real and Virtual Photon Production at Ultra-Low Transverse Momentum and Low Mass at the LHC". We provide an overview of the soft-photon puzzle, i.e., of the long-standing discrepancy between experimental data and predictions based on Low's soft-photon theorem, also referred to as "anomalous" soft photon production, and we review the current theoretical understanding of soft radiation and soft theorems. We also focus on low-mass dileptons as a tool for determining the electrical conductivity of the medium produced in high-energy nucleus-nucleus collisions. We discuss how both topics can be addressed with the planned ALICE 3 detector at the LHC.