dorsal/arxiv
View SchemaCompression and Expansion in Central Collisions
| Authors | P. Danielewicz |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/9704009 |
| URL | https://arxiv.org/abs/nucl-th/9704009 |
Abstract
Dynamics of central collisions of heavy nuclei in the energy range from few tens of MeV/nucleon to a couple of GeV/nucleon is discussed. As the beam energy increases and/or the impact parameter decreases, the maximum compression increases. It is argued that the hydrodynamic behavior of matter sets in the vicinity of balance energy. At higher energies shock fronts are observed to form within head-on reaction simulations, perpendicular to beam axis and separating hot compressed matter from cold. In the semicentral reactions a weak tangential discontinuity develops in-between these fronts. The hot compressed matter exposed to the vacuum in directions parallel to the shock fronts begins to expand collectively into these directions. The expansion affects particle angular distributions and mean energy components and further shapes of spectra and mean energies of particles emitted into any one direction. The variation of slopes and the relative yields measured within the FOPI collaboration are in a general agreement with the results of simulations. As to the FOPI data on stopping, they are consistent with the preference for transverse over the longitudinal motion in the head-on Au + Au collisions. Unfortunately, though, the data cannot be used to decide directly on that preference due to acceptance cuts. Tied to the spatial and temporal changes in the reactions are changes in the entropy per nucleon.
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"abstract": "Dynamics of central collisions of heavy nuclei in the energy range from few\ntens of MeV/nucleon to a couple of GeV/nucleon is discussed. As the beam energy\nincreases and/or the impact parameter decreases, the maximum compression\nincreases. It is argued that the hydrodynamic behavior of matter sets in the\nvicinity of balance energy. At higher energies shock fronts are observed to\nform within head-on reaction simulations, perpendicular to beam axis and\nseparating hot compressed matter from cold. In the semicentral reactions a weak\ntangential discontinuity develops in-between these fronts. The hot compressed\nmatter exposed to the vacuum in directions parallel to the shock fronts begins\nto expand collectively into these directions. The expansion affects particle\nangular distributions and mean energy components and further shapes of spectra\nand mean energies of particles emitted into any one direction. The variation of\nslopes and the relative yields measured within the FOPI collaboration are in a\ngeneral agreement with the results of simulations. As to the FOPI data on\nstopping, they are consistent with the preference for transverse over the\nlongitudinal motion in the head-on Au + Au collisions. Unfortunately, though,\nthe data cannot be used to decide directly on that preference due to acceptance\ncuts. Tied to the spatial and temporal changes in the reactions are changes in\nthe entropy per nucleon.",
"arxiv_id": "nucl-th/9704009",
"authors": [
"P. Danielewicz"
],
"categories": [
"nucl-th",
"nucl-ex"
],
"title": "Compression and Expansion in Central Collisions",
"url": "https://arxiv.org/abs/nucl-th/9704009"
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