Abstract
The physical processes behind the production of light nuclei in heavy ion collisions are unclear. The successful theoretical description of experimental yields by thermal models conflicts with the very small binding energies of the observed states, being fragile in such a hot and dense environment. Other available ideas are delayed production via coalescence, or a cooling of the system after the chemical freeze-out according to a Saha equation, or a ‘quench’ instead of a thermal freeze-out. A recently derived prescription of an (interacting) Hagedorn gas is applied to consolidate the above pictures. The tabulation of decay rates of Hagedorn states into light nuclei allows to calculate yields usually inaccessible due to very poor Monte Carlo statistics. Decay yields of stable hadrons and light nuclei are calculated. While the scale-free decays of Hagedorn states alone are not compatible with the experimental data, a thermalized hadron and Hagedorn state gas is able to describe the experimental data. Applying a cooling of the system according to a Saha-equation with conservation of nucleon and anti-nucleon numbers leads to (nearly) temperature independent yields, thus a production of the light nuclei at temperatures much lower than the chemical freeze-out temperature is compatible with experimental data and with the statistical hadronization model.
Highlights
In recent years, the production of light nuclei in relativistic heavy ion collisions has gained new interest
The tabulation of decay rates of Hagedorn states into light nuclei allows to calculate yields usually inaccessible due to very poor Monte Carlo statistics
Applying a cooling of the system according to a Saha-equation with conservation of nucleon and anti-nucleon numbers leads to temperature independent yields, a production of the light nuclei at temperatures much lower than the chemical freeze-out temperature is compatible with experimental data and with the statistical hadronization model
Summary
That a thermalized system has been built up, the binding energies of the observed states are so small, that a survival in such a virulent system of such fragile states at the chemical freeze-out temperatures of O(150 MeV) is improbable. The first ansatz is, that in the framework of coalescence, the production of high-mass resonances is governed by the yields of the lower mass states [4,5,6,7], while still energy conservation is not obeyed in this picture. Another explanation relies on the assumption of detailed balance, resp.
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