Beam energy dependent two-pion interferometry and the freeze-out eccentricity of pions in heavy ion collisions at STAR

Abstract

We present results of analyses of two-pion interferometry in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV measured in the STAR detector as part of the RHIC Beam Energy Scan program. The extracted correlation lengths (HBT radii) are studied as a function of beam energy, azimuthal angle relative to the reaction plane, centrality, and transverse mass ($m_T$) of the particles. The azimuthal analysis allows extraction of the eccentricity of the entire fireball at kinetic freeze-out. The energy dependence of this observable is expected to be sensitive to changes in the equation of state. A new global fit method is studied as an alternate method to directly measure the parameters in the azimuthal analysis. The eccentricity shows a monotonic decrease with beam energy that is qualitatively consistent with the trend from all model predictions and quantitatively consistent with a hadronic transport model.

arXiv comment27 pages; 27 figures

References in corpus (58)

• Experimental and Theoretical Challenges in the Search for the Quark Gluon Plasma: The STAR Collaboration's Critical Assessment of the Evidence from RHIC Collisions
• Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
• Quark Gluon Plasma an Color Glass Condensate at RHIC? The perspective from the BRAHMS experiment
• The PHOBOS Perspective on Discoveries at RHIC
• The order of the quantum chromodynamics transition predicted by the standard model of particle physics
• Methods for analyzing anisotropic flow in relativistic nuclear collisions
• Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
• Is there still any Tc mystery in lattice QCD? Results with physical masses in the continuum limit III
• The STAR Time Projection Chamber: A Unique Tool for Studying High Multiplicity Events at RHIC
• Femtoscopy in Relativistic Heavy Ion Collisions: Two Decades of Progress
• On the Phase Diagram of QCD
• QCD Equation of State and Hadron Resonance Gas
• Color Superconductivity and Chiral Symmetry Restoration at Nonzero Baryon Density and Temperature
• Energy Dependence of Moments of Net-proton Multiplicity Distributions at RHIC
• Pion and kaon production in central Pb+Pb collisions at 20A and 30A GeV: Evidence for the onset of deconfinement
• Universality, the QCD critical/tricritical point and the quark number susceptibility
• Chiral Phase Transition within Effective Models with Constituent Quarks
• Two-pion Bose-Einstein correlations in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Observable implications of geometrical and dynamical aspects of freeze-out in heavy ion collisions
• Pion interferometry in Au+Au collisions at $\sqrt{{\mathrm{s}}_{{}_{\mathrm{NN}}}}$ = 200 GeV
• Beam-Energy Dependence of Directed Flow of Protons, Antiprotons and Pions in Au+Au Collisions
• The Time-Delay Signature of Quark-Gluon-Plasma Formation in Relativistic Nuclear Collisions
• Hydrodynamics near the QCD Phase Transition: Looking for the Longest-Lived Fireball
• Beam-energy dependence of charge separation along the magnetic field in Au+Au collisions at RHIC
• Inclusive charged hadron elliptic flow in Au + Au collisions at $\sqrt{s_{NN}}$ = 7.7 - 39 GeV
• Directed and Elliptic Flow in 158 GeV/Nucleon Pb + Pb Collisions
• Elliptic flow of identified hadrons in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7--62.4 GeV
• Systematic parameter study of hadron spectra and elliptic flow from viscous hydrodynamic simulations of Au+Au collisions at sqrt(s_NN) = 200 GeV
• A new cross term in the two-particle Hanbury-Brown-Twiss correlation function
• Proton and Pion Production Relative to the Reaction Plane in Au + Au Collisions at AGS Energies
• Energy and Charged Particle Flow in 10.8 A GeV/c Au+Au Collisions
• Pion Interferometry at RHIC: Probing a thermalized Quark-Gluon-Plasma?
• Observation of an energy-dependent difference in elliptic flow between particles and anti-particles in relativistic heavy ion collisions
• Azimuthally sensitive Hanbury Brown-Twiss interferometry in Au+Au collisions at sqrt(s_{NN}) = 200 GeV
• Beam Energy and Centrality Dependence of Two-Pion Bose-Einstein Correlations at SPS Energies
• Universal Pion Freeze-out in Heavy-Ion Collisions
• Extracting Source Parameters from Gaussian Fits to Two-Particle Correlations
• Collision Energy Dependence of Viscous Hydrodynamic Flow in Relativistic Heavy-Ion Collisions
• Transverse Momentum Dependence of Hanbury-Brown/Twiss Correlation Radii
• Spinodal phase separation in relativistic nuclear collisions
• Source Dimensions in Ultrarelativistic Heavy Ion Collisions
• Azimuthal Dependence of Pion Interferometry at the AGS
• Bose-Einstein correlations of pion pairs in central Pb+Pb collisions at CERN SPS energies
• The effect of "pre-formed" hadron potentials on the dynamics of heavy ion collisions and the HBT puzzle
• Symmetry constraints for the emission angle dependence of Hanbury Brown--Twiss radii
• Pion femtoscopy in p+p collisions at sqrt(s)=200 GeV
• Lifetimes and Sizes from Two-Particle Correlation Functions
• Bootstraping the QCD Critical Point
• System, centrality, and transverse mass dependence of two-pion correlation radii in heavy ion collisions at 11.6 and 14.6 A-GeV
• Transverse Momentum and Rapidity Dependence of HBT Correlations in Au+Au Collisions at sqrt(s_NN) = 62.4 and 200 GeV
• Shape analysis of strongly-interacting systems: the heavy ion case
• Correspondence between HBT radii and the emission zone in non-central heavy ion collisions
• Azimuthal dependence of pion source radii in Pb+Au collisions at 158 A GeV
• Transport model analysis of particle correlations in relativistic heavy ion collisions at femtometer scales
• Combined effects of nuclear Coulomb field, radial flow, and opaqueness on two-pion correlations
• Transport model analysis of the transverse momentum and rapidity dependence of pion interferometry at SPS energies
• System-size dependence of the pion freeze-out volume as a potential signature for the phase transition to a Quark Gluon Plasma
• Two-pion Bose-Einstein correlations in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV measured with the ALICE experiment