Enhanced production of low-mass electron-positron pairs in 40-AGeV Pb-Au collisions at the CERN SPS

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 ne...

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Detalles Bibliográficos
Autores principales: Adamova, D., Agakichiev, G., Appelshauser, H., Belaga, V., Braun-Munzinger, P., Cherlin, A., Damjanovic, S., Dietel, T., Dietrich, L., Drees, A., Esumi, S.I., Filimonov, K., Fomenko, K., Fraenkel, Z., Garabatos, C., Glassel, P., Hering, G., Holeczek, J., Kushpil, V., Lenkeit, B., Maas, A., Marin, A., Milosevic, J., Milov, A., Miskowiec, D., Panebrattsev, Yu., Petchenova, O., Petracek, V., Pfeiffer, A., Rak, J., Ravinovich, I., Rehak, P., Richter, M., Sako, H., Schmitz, W., Sedykh, S., Seipp, W., Sharma, A., Shimansky, S., Slivova, J., Specht, H.J., Stachel, J., Sumbera, M., Tilsner, H., Tserruya, I., Wessels, J.P., Wienold, T., Windelband, B., Wurm, J.P., Xie, W., Yurevich, S., Yurevich, V.
Lenguaje:eng
Publicado: 2002
Materias:
Nuclear Physics - Experiment
Acceso en línea:https://dx.doi.org/10.1103/PhysRevLett.91.042301
http://cds.cern.ch/record/582888
Descripción
Sumario: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.

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