PHENIX results on fluctuations and Bose-Einstein correlations in Au+Au collisions from the RHIC Beam Energy Scan

TL;DR

This paper reports on PHENIX measurements of fluctuations and Bose-Einstein correlations in Au+Au collisions across a range of energies, aiming to explore the QCD phase diagram and locate the critical end point.

Contribution

It provides new experimental results on net-charge fluctuations and two-pion correlations at multiple energies, contributing to the search for the QCD critical point.

Findings

High-order cumulants of net-charge fluctuations measured.

Source radii compared across energies and collision systems.

Results inform the search for the QCD critical point.

Abstract

The RHIC Beam Energy Scan focuses on mapping the QCD phase diagram and pinpointing the location of a possible critical end point. Bose-Einstein correlations and event-by-event fluctuations of conserved quantities, measured as a function of centrality and collision energy, are promising tools in these studies. Recent lattice QCD and statistical thermal model calculations predict that higher-order cumulants of the fluctuations are sensitive indicators of the phase transition. Products of these cumulants can be used to extract the freeze-out parameters (1) and to locate the critical point (2). Two-pion interferometry measurements are predicted to be sensitive to potential softening of the equation of state and prolonged emission duration close to the critical point (3). We present recent PHENIX results on fluctuations of net-charge using high-order cumulants and their products in Au+Au collisions at \sqsn = 7.7 - 200 GeV, and measurement of two-pion correlation functions and emission-source radii in Cu+Cu and Au+Au collisions at several beam energies. The extracted source radii are compared to previous measurements at RHIC and LHC in order to study energy dependence of the specific quantities sensitive to expansion velocity and emission duration. Implications for the search of a critical point and baryon chemical potentials at various collision energies are discussed.