Selected highlights of the production of light (anti-)(hyper-)nuclei in ultra-relativistic heavy-ion collisions

Abstract

The production of light (anti-)nuclei and (anti-)hypernuclei in ultra-relativistic heavy-ion collisions, but also in more elementary collisions as proton–proton and proton–nucleus collisions, became recently a focus of interest. In particular, the fact that these objects are all loosely bound compared to the temperature and energies, e.g. the kinetic energies involved, is often stressed out to be special for their production. The binding energies of these (anti-)nuclei is between 130 keV ($${\mathrm {\Lambda }}$$ Λ separation energy in the hypertriton) and about 8 MeV per nucleon. Whereas the connected temperatures are of the order of 100 to 160 MeV. This lead to some difficulties in the interpretation of the usually discussed production models, i.e. coalescence and statistical-thermal models, as will be discussed here. In this brief review we discuss selected highlights of the production of light (anti-)nuclei, such as (anti-)deuteron, (anti-)helium and (anti-)alpha nuclei. In addition, we will discuss the current status of the highly debated lifetime of the (anti-)hypertriton and connected measurements and model results.

Deuteron yields from LHC: Continuum correlations and in-medium effects

“…The most extreme example, displayed also in Fig. I and discussed intensively in [16,17] is the hypertriton 3 Λ H, a bound state of a proton, a neutron and a Λ hyperon. The object can be imagined as a deuteron core surrounded by the Λ in form of a ultra-halo nucleus (size of about 10.8 fm [16,77]).…”

“…These correlations in the deuteron channel are considered as precursors of the deuterons observed as the final deuteron yields. A similar concept is used in the coalescence model [17,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Baryon pre-clusters are also discussed in [83][84][85] in a slightly different approach.…”

“…composition, momentum distribution of components, etc.) of this extreme matter are reconstructed from measured yields, transverse-momentum spectra and correlations [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The production yields of composite particles, i.e.…”

“…The production yields of composite particles, i.e. light (anti-)(hyper-)nuclei, in Pb-Pb collisions are very successfully explained by thermal [15,18,19] and coalescence models [17,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. There, thermodynamic equilibrium is assumed at freeze-out, and this determines a primordial distribution of the components of hot and dense matter.…”

Relativistic kinetic approach to light nuclei production in high-energy nuclear collisions

“…Other proposed mechanisms for light nuclei production in highenergy nuclear collisions include the decay of a compact quark droplet [23] or pre-formed nuclear clusters [24]. In spite of these efforts, the production mechanism of light (anti-)(hyper-)nuclei in nuclear collisions has not yet been unambiguously understood [25][26][27].…”