Dilepton production in proton-nucleus and nucleus-nucleus collisions at SPS energies |
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| Affiliation: | 1. Cyclotron Institute and Physics Department, Texas A&M University, College Station, TX 77843, USA;2. Department of Physics, State University of New York at Stony Brook, Stony Brook, NY 11974, USA;1. Institute for Physical Problems, Baku State University, Az-1148 Baku, Azerbaijan;2. Department of Physics, Doǧuş University, Acibadem-Kadiköy, 34722 Istanbul, Turkey;3. School of Physics, Institute for Research in Fundamental Sciences (IPM), P. O. Box 19395-5531, Tehran, Iran;4. Department of Physics, Kocaeli University, 41380 Izmit, Turkey;1. Institute for Physical Problems, Baku State University, Az-1148 Baku, Azerbaijan;2. Department of Physics, Doǧuş University, Acibadem-Kadiköy, 34722 Istanbul, Turkey;3. Department of Physics, Kocaeli University, 41380 Izmit, Turkey;1. Instituto de Física Teórica, Universidade Estadual Paulista, Rua Dr. Bento Teobaldo Ferraz, 271 - Bloco II, 01140-070 São Paulo, SP, Brazil;2. ARC Centre of Excellence for Particle Physics at the Terascale and CSSM, School of Physical Sciences, Department of Physics, The University of Adelaide, Adelaide SA 5005, Australia;3. Laboratório de Física Teórica e Computacional, Universidade Cruzeiro do Sul, Rua Galvão Bueno, 868, Liberdade 01506-000, São Paulo, SP, Brazil;1. Department of Physics and Astronomy ‘Ettore Majorana’, University of Catania, Via S. Sofia 64, 1-95125 Catania, Italy;2. Laboratori Nazionali del Sud, INFN-LNS, Via S. Sofia 62, I-95123 Catania, Italy;3. School of Physical Sciences, Indian Institute of Technology Goa, Ponda, 403401, Goa, India |
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| Abstract: | Dilepton production in proton- and nucleus-induced reactions is studied in the relativistic transport model using initial conditions determined by the string dynamics from RQMD. It is found that both the CERES and HELIOS-3 data for dilepton spectra in proton-nucleus reactions can be well described by the ‘conventional’ mechanism of Dalitz decay and direct vector meson decay. However, to provide a quantitative explanation of the observed dilepton spectra in central S+Au and S+W collisions requires contributions other than these direct decays. Introducing a decrease of vector meson masses in hot and dense medium, we find that these heavy-ion data can also be satisfactorily explained. This agrees with our earlier conclusions based on a fire-cylinder model. We also give predictions for Pb+Au collisions at 160 GeV/nucleon using current CERES mass resolution and acceptance. |
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