Abstract
We report on first measurements of low-mass electron-positron pairs in Pb-Au collisions at the CERN SPS beam energy of . The observed pair yield integrated over the range of invariant masses is enhanced over the expectation from neutral meson decays by a factor of , somewhat larger than previously observed at the higher energy of . The results are discussed with reference to model calculations based on annihilation with a modified propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the are more driven by baryon density than by temperature.
- Received 25 September 2002
DOI:https://doi.org/10.1103/PhysRevLett.91.042301
©2003 American Physical Society