Energy dependence of acceptance-corrected dielectron excess mass spectrum at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}=19.6$ and 200 GeV

Abstract

The acceptance-corrected dielectron excess mass spectra, where the known hadronic sources have been subtracted from the inclusive dielectron mass spectra, are reported for the first time at mid-rapidity $|y_{ee}|<1$ in minimum-bias Au+Au collisions at $\sqrt{s_{NN}}$ = 19.6 and 200 GeV. The excess mass spectra are consistently described by a model calculation with a broadened $\rho$ spectral function for $M_{ee}<1.1$ GeV/$c^2$. The integrated dielectron excess yield at $\sqrt{s_{NN}}$ = 19.6 GeV for $0.4<M_{ee}<0.75$ GeV/$c^2$, normalized to the charged particle multiplicity at mid-rapidity, has a value similar to that in In+In collisions at $\sqrt{s_{NN}}$ = 17.3 GeV. For $\sqrt{s_{NN}}$ = 200 GeV, the normalized excess yield in central collisions is higher than that at $\sqrt{s_{NN}}$ = 17.3 GeV and increases from peripheral to central collisions. These measurements indicate that the lifetime of the hot, dense medium created in central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV is longer than those in peripheral collisions and at lower energies.

9 pages, 6 figures

References in corpus (10)

• Systematic Measurements of Identified Particle Spectra in pp, d+Au and Au+Au Collisions from STAR
• Measurement of high-p_T Single Electrons from Heavy-Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV
• Comprehensive Interpretation of Thermal Dileptons at the SPS
• Evidence for the production of thermal muon pairs with masses above 1 GeV/c^2 in 158A GeV Indium-Indium Collisions
• Modification of the rho meson detected by low-mass electron-positron pairs in central Pb-Au collisions at 158 A GeV/c
• Evidence for radial flow of thermal dileptons in high-energy nuclear collisions
• NA60 results on the rho spectral function in In-In collisions
• Systematics of Kinetic Freeze-out Properties in High Energy Collisions from STAR
• Electromagnetic Probes at RHIC-II
• Di-electron spectrum at mid-rapidity in $p+p$ collisions at $\sqrt{s}=200$ GeV

Cited by in corpus (17)

• Properties of hot and dense matter from relativistic heavy ion collisions
• Properties of the QCD Matter -- An Experimental Review of Selected Results from RHIC BES Program
• Low-$p_T$ $e^{+}{e}^{-}$ pair production in Au$+$Au collisions at $\sqrt{s_{NN}}$ = 200 GeV and U$+$U collisions at $\sqrt{s_{NN}}$ = 193 GeV at STAR
• The Present and Future of QCD
• Coherent lepton pair production in hadronic heavy ion collisions
• Chiral spin symmetry and the QCD phase diagram
• Rate and ellipticity of dilepton production in a magnetized quark-gluon plasma
• Virtual Photons Shed Light on the Early Temperature of Dense QCD Matter
• Dilepton production at next-to-leading order and intermediate invariant-mass observables
• Chiral spin symmetry and hot/dense QCD
• Energy, centrality and momentum dependence of dielectron production at collider energies in a coarse-grained transport approach
• Exploring the properties of the phases of QCD matter - research opportunities and priorities for the next decade
• Multimessenger study of baryon-charged QCD matter in heavy-ion collisions
• Measurement of inclusive electrons from open heavy-flavor hadron decays in $p$+$p$ collisions at $\sqrt{s}=200$ GeV with the STAR detector
• Overview of recent results from the STAR experiment
• Electromagnetic & Weak Probes: Experimental Overview
• Simultaneous Production of Lepton Pairs at Ultra-peripheral Relativistic Heavy Ion Collisions