(Anti-)Nucleosynthesis in the Little and the Big Bang

4/2-011 - TH common room (CERN)

4/2-011 - TH common room


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Francesca Bellini (CERN), Volodymyr Vovchenko (Goethe University Frankfurt)

The experimental data on light (anti-)(hyper-)nuclei at the LHC are consistent with the thermal production of these loosely-bound objects at the chemical-freeze out of the hadronic system produced in heavy-ion collisions. At the same time, an observation of suppressed short-lived resonance yields, as well as of a lower kinetic freeze-out temperature characterizing the pT spectra of both hadrons and nuclei, indicate that the system undergoes a long-lasting hadronic phase. These observations together pose the ``(anti-)nuclei puzzle'': how can loosely-bound composite objects survive the hadronic phase given that their binding energies (few MeV or less) are much lower than the characteristic temperatures in the hadronic phase (T ~ 100-150 MeV)? 

This is addressed here by making use of the analogy between the evolution of the early Universe after the Big Bang and that of "Little Bangs" created in the laboratory. Assuming that disintegration and regeneration reactions involving light nuclei proceed in relative chemical equilibrium after the chemical freeze-out of hadrons, their abundances are determined through the famous cosmological Saha equation of primordial nucleosynthesis and show no exponential dependence on the temperature typical for the thermal model. A quantitative analysis, taking into account the feeddown of nucleons and hyperons from the short-lived resonances, shows agreement with the experimental data for the entire range of temperatures corresponding to the hadronic phase.

Further reading:

The Saha equation approach to nucleosynthesis at the LHC

Comparison of the thermal and coalescence approaches

ALICE results on the production of (anti-)(hyper-)nuclei

ALICE results on the production of short-lived resonances

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