Production of 4He and 4He‾ in Pb–Pb collisions at sNN

Nucleosynthesis in heavy-ion collisions at the LHC via the Saha equation

“…Assuming that strong 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 nuclear equivalent of the Saha ionization equation, where the strong exponential dependence on the temperature typical for the standard thermal model is eliminated. A quantitative analysis, performed using the hadron resonance gas model in partial chemical equilibrium, shows agreement with the experimental data of the ALICE collaboration on d, 3 He, 3 Λ H, and 4 He yields for a very broad region of temperatures well below the chemical freeze-out, T 155 MeV. Here we focused at the LHC, but the formalism can as well be considered at lower collision energies, such as RHIC or SPS.…”

“…Figure 3 presents the temperature dependence of ratios of various light (hyper-)nuclei to the yields of protons at T < T ch . These include d, 3 He, 4 [38]. As we work here with net baryon free matter, the results for anti-nuclei are identical.…”

“…Introduction. The yields of light (anti-)(hyper-)nuclei such as deuteron (d), helium-3 ( 3 He), hypertriton ( 3 Λ H), and helium-4 ( 4 He) have recently been measured in Pb-Pb collisions at the LHC by the AL-ICE collaboration [1][2][3]. Common approaches used to describe the production of these loosely-bound objects include the thermal-statistical approach [4][5][6][7][8] and the coalescence model [9][10][11][12], a determination of the production mechanism is of great interest [see, e.g., Refs.…”

“…These observations suggest that certain thermal aspects are present in the production mechanism of loosely-bound objects. On the other hand, a survival of these fragile objects in hot and dense thermal environment at T = T ch all the way to their detection would seem surprising, given their small binding energies relative to the system temperature (the binding energy of deuteron and Λ in 3 Λ H is of order 130 keV [24]), and, for instance, the known large pion-deuteron break-up cross section [25]. We aim to shed light on this question by making use of an analogy between the post-chemical freeze-out expansion of matter in heavy-ion collisions at the LHC and primordial nucleosynthesis stage in the early universe.…”

Baryon preclustering at the freeze-out of heavy-ion collisions and light-nuclei production

“…If the experimental reconstruction of α particles [35] can be performed in these low-energy collisions, and their multiplicity measured with certain level of confidence, these ratios would prove the sensitivity of the N N potential to the presence of a near-by critical point. (27,28,29) as a function of the collision energy computed from the ratio (26) in [5] assuming the only effect of the N N potential modification.…”