Enhanced Production of Low-Mass Electron Pairs in 40 AGeV Pb-Au Collisions at the CERN SPS

Abstract

We report on first measurements of low-mass electron pairs in Pb-Au collisions at the lower SPS beam energy of 40 AGeV. The pair yield integrated over the range of invariant masses 0.2<m<1 GeV/c^2 is enhanced by a factor of 5.1+-1.3(stat)+-1.0/1.5(syst data/decays) over the expectation from neutral meson decays, more than previously observed at the higher energy of 158 AGeV. The results are discussed with reference to model calculations based on pi+ pi- -> e+ e- annihilation with a modified rho-propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the rho are more driven by baryon density than by temperature.

4 pages, 3 figures final version as printed

References in corpus (9)

• Rho Meson Propagation and Dilepton Enhancement in Hot Hadronic Matter
• Enhancement of low-mass dileptons in heavy-ion collisions
• Low-mass e+e- pair production in 158 A GeV Pb-Au collisions at the CERN SPS, its dependence on multiplicity and transverse momentum
• Low-Mass Dileptons at the CERN-SpS: Evidence for Chiral Restoration?
• On the Manifestation of Chiral Symmetry in Nuclei and Dense Nuclear Matter
• Medium Modifications of the Rho Meson at CERN/SPS Energies
• Universal Pion Freeze-out in Heavy-Ion Collisions
• Recent results from Pb-Au collisions at 158 GeV/c per nucleon obtained with the CERES spectrometer
• Latest Results from CERES/NA45

Cited by in corpus (83)

• Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
• Properties of hot and dense matter from relativistic heavy ion collisions
• Hadronic Production of Thermal Photons
• Charmonium and bottomonium production in heavy-ion collisions
• Dilepton Radiation at the CERN Super Proton Synchrotron
• Hadrons in strongly interacting matter
• Comprehensive Interpretation of Thermal Dileptons at the SPS
• e+e--pair production in Pb-Au collisions at 158 GeV per nucleon
• Dielectron production in 12C+12C collisions at 2 AGeV with HADES
• Modification of the rho meson detected by low-mass electron-positron pairs in central Pb-Au collisions at 158 A GeV/c
• 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 Chiral Restoration Transition of QCD and Low Mass Dileptons
• Measurements of Dielectron Production in Au$+$Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV from the STAR Experiment
• Study of dielectron production in C+C collisions at 1 AGeV
• Dielectron Mass Spectra from Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV
• A Hadron Blind Detector for the PHENIX Experiment at RHIC
• Equilibrium Statistical-Thermal Models in High-Energy Physics
• Dilepton production in proton-induced reactions at SIS energies with the GiBUU transport model
• Dilepton production in nucleus-nucleus collisions at top SPS energy within the Parton-Hadron-String Dynamics (PHSD) transport approach
• Coherent lepton pair production in hadronic heavy ion collisions
• Low mass dilepton production at ultrarelativistic energies
• 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
• The CERES/NA45 Radial Drift Time Projection Chamber
• Leptonic and charged kaon decay modes of the $\varphi$ meson measured in heavy-ion collisions at the CERN SPS
• Production of the $\rho$(770)${}^0$ meson in pp and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Inclusive omega photoproduction off nuclei
• New results from CERES
• Dilepton production in proton-proton and quasifree proton-neutron reactions at 1.25 GeV
• Photon and dilepton production at the Facility for Antiproton and Ion Research and the beam energy scan program at the Relativistic Heavy-Ion Collider using coarse-grained microscopic transport simulations
• A chiral lagrangian with Broken Scale: testing the restoration of symmetries in astrophysics and in the laboratory
• Dilepton Radiation from Strongly Interacting Systems
• Dilepton production from hot hadronic matter in nonequilibrium
• Photoproduction of ${\eta }^{\prime }$ mesons off nuclei and their properties in the nuclear medium
• Study of the $\rho$ and $\omega$ meson decays into pseudoscalar meson and $e^{+}{e}^{-}$ pair with the CMD-2 detector
• Surface and volume effects in the photoabsorption of nuclei
• Double pion photoproduction off 40Ca
• Delta(1232) and Nucleon Spectral Functions in Hot Hadronic Matter
• Thermal Electromagnetic Radiation in Heavy-Ion Collisions
• Resonances as a possible observable of hot and dense nuclear matter
• Photoproduction of mesons from nuclei - In-medium properties of hadrons
• The Vector Probe in Heavy-Ion Reactions
• Ultrarelativistic nucleus-nucleus collisions and the quark-gluon plasma
• Photoproduction of $\eta$-mesons off C and Cu nuclei for photon energies below 1.1 GeV
• Dielectron production in proton-proton collisions at $\sqrt{s}$ = 7 TeV
• Electromagnetic probes
• Electromagnetic Probes
• Thermal production of the $\rho$ meson in the ${\pi }^{+}{\pi }^{-}$ channel
• Cherenkov gluons (predictions and proposals)
• Dilepton production in microscopic transport theory with in-medium $\rho$-meson spectral function
• The SPS Heavy Ion Programme
• Finite temperature pion vector form factors in Chiral Perturbation Theory
• Dilepton production in nucleon-nucleon collisions reexamined
• SPS energy scan results and physics prospects at FAIR
• Dileptons and Medium Effects in Heavy-Ion Collisions
• High $p_T$ resonances as a possibility to explore hot and dense nuclear matter
• Update on Chiral Symmetry Restoration in the Context of Dilepton Data
• Lepton-pair production in nuclear collisions - past, present, future
• Finite-width QCD sum rules for rho and omega mesons
• Hadron Blind Cherenkov Counters
• A Hadron Blind Detector for the PHENIX Experiment
• QCD in the nuclear medium and effects due to Cherenkov gluons
• Heavy-quark azimuthal momentum correlations as a sensitive probe of thermalization
• Letter of Intent: the NA60+ experiment
• Dilepton production at SIS energies with the GiBUU transport model
• Two Pion Production in Photon Induced Reactions
• In-Medium Properties of Hadrons
• Dielectron production in 200 GeV p+p and Au+Au collisions at STAR
• Inclusive Photoproduction of $\eta$ Mesons on Nuclei and the in-medium properties of the S${}_{11}$ Resonance
• The Delta(1232) at RHIC
• Dielectron production in Au$+$Au collisions at $\sqrt{s_{NN}}$=200 GeV
• Prompt production of D mesons with ALICE at the LHC
• Asymmetric vector mesons produced in nuclear collisions
• Dilepton production in nucleon-nucleon collisions around 1 GeV/nucleon: a theoretical update
• Variation of hadron masses in nuclear matter in the relativistic Hartree approximation
• Dileptons from the nonequilibrium Quark-Gluon Plasma
• Mass of the rho^0 meson in ultra-relativistic heavy-ion collision
• Heavy-ion physics at the CERN SPS H2: NA35, NA49 and NA61/SHINE (with personal recollections)
• Double Pion Photoproduction from Nuclei
• Hadrons in Nuclei: Experiments and Perspectives
• Dileptons and Direct Photons at SPS
• Heavy lepton pair production in nucleus-nucleus collisions at LHC energy - a case study
• Dilepton production from hydrodynamically expanding fireball
• Electromagnetic Radiation and in-Medium Effects