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

D. Adamová et al. (CERES/NA45 Collaboration)
Phys. Rev. Lett. 91, 042301 – Published 22 July 2003

Abstract

We report on first measurements of low-mass electron-positron pairs in Pb-Au collisions at the CERN SPS beam energy of 40AGeV. The observed pair yield integrated over the range of invariant masses 0.2<m1GeV/c2 is enhanced over the expectation from neutral meson decays by a factor of 5.9±1.5(stat)±1.2(syst   data)±1.8(systmeson   decays), somewhat larger than previously observed at the higher energy of 158AGeV. The results are discussed with reference to model calculations based on π+πe+e annihilation with a modified ρ propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the ρ are more driven by baryon density than by temperature.

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  • Received 25 September 2002

DOI:https://doi.org/10.1103/PhysRevLett.91.042301

©2003 American Physical Society

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Vol. 91, Iss. 4 — 25 July 2003

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