Thermal dileptons from coarse-grained transport as fireball probes at SIS energies
| Pub type: | Article |
| Citation: | Galatyuk2016 |
| Status: | Published |
| Journal: | The European Physical Journal A |
| Volume: | 52 |
| Number: | 5 |
| Year: | 2016 |
| Month: | May |
| Pages: | 131 |
| ISSN: | 1434-601X |
| URL: | https://link.springer.com/arti... |
| DOI: | 10.1140/epja/i2016-16131-1 |
| Abstract: | Utilizing a coarse-graining method to convert hadronic transport simulations of Au+Au collisions at SIS energies into local temperature, baryon and pion densities, we compute the pertinent radiation of thermal dileptons based on an in-medium {\$} {\backslash}rho{\$} spectral function that describes available spectra at ultrarelativistic collision energies. In particular, we analyze how far the resulting yields and slopes of the invariant-mass spectra can probe the lifetime and temperatures of the fireball. We find that dilepton radiation sets in after the initial overlap phase of the colliding nuclei of about 7fm/c, and lasts for about 13fm/c. This duration closely coincides with the development of the transverse collectivity of the baryons, thus establishing a direct correlation between hadronic collective effects and thermal EM radiation, and supporting a near local equilibration of the system. This fireball ``lifetime'' is substantially smaller than the typical 20-30fm/c that naive considerations of the density evolution alone would suggest. We furthermore find that the total dilepton yield radiated into the invariant-mass window of {\$} M=0.3{\$} -0.7GeV/c^2 normalized to the number of charged pions, follows a relation to the lifetime found earlier in the (ultra-) relativistic regime of heavy-ion collisions, and thus corroborates the versatility of this tool. The spectral slopes of the invariant-mass spectra above the {\$} {\backslash}phi{\$} -meson mass provide a thermometer of the hottest phases of the collision, and agree well with the maximal temperatures extracted from the coarse-grained hadron spectra. |
| Month_val: | 5 |
| Authors: | |
| Added by: | [DGM] |
| Total mark: | 0 |
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