Measurements of dielectron production in Au + Au collisions atsNN=200GeV from the STAR experiment

2015/04/06 by STAR Collaboration, L. Adamczyk, J. K. Adkins +339 · 1 citation
Physics and Astronomy · #Hadron #High-Energy Particle Collisions Research #Invariant mass #Meson #Nuclear physics #Nucleon #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #hep-ex #nucl-ex

paper · pdf · doi:10.1103/physrevc.92.024912

published as Phys. Rev. C 92, 024912 (2015) · 40 pages, 49 figures

arxiv created 2015/04/06 · openalex publication_date 2015/08/24 · arxiv updated 2015/09/02 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06

Abstract

We report on measurements of dielectron (e⁺e^\ensuremath-) production in Au+Au collisions at a center-of-mass energy of 200 GeV per nucleon-nucleon pair using the STAR detector at BNL Relativistic Heavy Ion Collider. Systematic measurements of the dielectron yield as a function of transverse momentum (p_T) and collision centrality show an enhancement compared to a cocktail simulation of hadronic sources in the low invariant-mass region (M_ee<1\phantom\rule4pt0exGeV/c²). This enhancement cannot be reproduced by the \ensuremathρ-meson vacuum spectral function. In minimum-bias collisions, in the invariant-mass range of 0.30--0.76\phantom\rule4.pt0exGeV/c², integrated over the full p_T acceptance, the enhancement factor is 1.76\ifmmode±\else\textpm\fi0.06\phantom\rule0.28em0ex(stat.)\ifmmode±\else\textpm\fi0.26\phantom\rule0.28em0ex(sys.)\ifmmode±\else\textpm\fi0.29\phantom\rule0.28em0ex(cocktail). The enhancement factor exhibits weak centrality and p_T dependence in STAR's accessible kinematic regions, while the excess yield in this invariant-mass region as a function of the number of participating nucleons follows a power-law shape with a power of 1.44\ifmmode±\else\textpm\fi0.10. Models that assume an in-medium broadening of the \ensuremathρ-meson spectral function consistently describe the observed excess in these measurements. Additionally, we report on measurements of \ensuremathω- and \ensuremathφ-meson production through their e⁺e^\ensuremath- decay channel. These measurements show good agreement with Tsallis blast-wave model predictions, as well as, in the case of the \ensuremathφ meson, results through its K⁺K^\ensuremath- decay channel. In the intermediate invariant-mass region (1.1<M_ee<3\phantom\rule4pt0exGeV/c²), we investigate the spectral shapes from different collision centralities. Physics implications for possible in-medium modification of charmed hadron production and other physics sources are discussed.

Citations

• Dielectron Mass Spectra fromAu+AuCollisions atsNN=200 GeV
• RHIC project overview
• Dimuon transverse momentum spectra as a tool to characterize the emission region in heavy-ion collisions
• Dielectron azimuthal anisotropy at mid-rapidity in Au + Au collisions atsNN=200GeV
• First Results on Angular Distributions of Thermal Dileptons in Nuclear Collisions
• Comprehensive Interpretation of Thermal Dileptons Measured at the CERN Super Proton Synchrotron
• The STAR time projection chamber: a unique tool for studying high multiplicity events at RHIC
• Evidence for Radial Flow of Thermal Dileptons in High-Energy Nuclear Collisions
• Experimental and theoretical challenges in the search for the quark–gluon plasma: The STAR Collaboration's critical assessment of the evidence from RHIC collisions
• Suppressedπ0Production at Large Transverse Momentum in CentralAu+AuCollisions atsNN=200 GeV
• Spectra and radial flow in relativistic heavy ion collisions with Tsallis statistics in a blast-wave description

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