The impact of energy conservation in transport models on the π−/π+ multiplicity ratio in heavy-ion collisions and the symmetry energy
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- 作者：M.D. Cozma dan.cozma@theory.nipne.ro" class="auth_mail" title="E-mail the corresponding author
- 关键词：Equation of state of nuclear matter ; Quantum molecular dynamics ; Heavy-ion collisions ; Symmetry energy
- 刊名：Physics Letters B
- 出版年：2016
- 出版时间：10 February 2016
- 年：2016
- 卷：753
- 期：Complete
- 页码：166-172
- 全文大小：456 K
文摘
The charged pion multiplicity ratio in intermediate energy central heavy-ion collisions has been proposed as a suitable observable to constrain the high density dependence of the isovector part of the equation of state. A comparison of various transport model predictions with existing experimental data has led, however, to contradictory results. Using an upgraded version of the Tübingen QMD transport model, which allows the conservation of energy at a local or global level by accounting for the potential energy of hadrons in two-body collisions and leading thus to particle production threshold shifts, we demonstrate that compatible constraints for the symmetry energy stiffness can be extracted from pion multiplicity and elliptic flow observables. However, pion multiplicities and ratios are proven to be highly sensitive to the yet unknown isovector part of the in-medium Δ(1232) potential which hinders, at present, the extraction of meaningful information on the high density dependence of the symmetry energy. A solution to this problem together with the inclusion of contributions presently neglected, such as in-medium pion potentials and retardation effects, are needed for a final verdict on this topic.