Abstract
We present a detailed comparison of coalescence and thermal-statistical models for the production of (anti-)(hyper-)nuclei in high-energy collisions. For the first time, such a study is carried out as a function of the size of the object relative to the size of the particle emitting source. Our study reveals large differences between the two scenarios for the production of objects with extended wave-functions. While both models give similar predictions and show similar agreement with experimental data for (anti-)deuterons and (anti-)3He nuclei, they largely differ in their description of (anti-)hyper-triton production. We propose to address experimentally the comparison of the production models by measuring the coalescence parameter systematically for different (anti-)(hyper-)nuclei in different collision systems and differentially in multiplicity. Such measurements are feasible with the current and upgraded Large Hadron Collider experiments. Our findings highlight the unique potential of ultra-relativistic heavy-ion collisions as a laboratory to clarify the internal structure of exotic QCD objects and can serve as a basis for more refined calculations in the future.
Highlights
Nuclei and hypernuclei are special objects with respect to noncomposite hadrons, because their size is comparable to a fraction or the whole system created in high-energy proton-proton, proton-nucleus, and nucleus-nucleus (AA) collisions [1]
We summarize our main conclusions as follows: (1) For the production of A = 2 and A = 3nuclei in heavy-ion collisions, thermal + blast-wave and coalescence models give similar predictions for a source volume that is constrained by experimental data on d, dproduction in central Pb-Pb collisions
The yield of hypertriton appears to be suppressed by about two orders of magnitude in pp collisions with respect to 3He due to its wider wave function
Summary
Nuclei and hypernuclei are special objects with respect to noncomposite hadrons (pions, protons, etc.), because their size is comparable to a fraction or the whole system created in high-energy proton-proton (pp), proton-nucleus (pA), and nucleus-nucleus (AA) collisions [1]. Once the mean free path for elastic collisions is larger than the system size, the fireball freezes out kinetically at Tkin ≈ 90 MeV [14] In such a dense and hot environment, composite objects with binding energies that are low with respect to the temperature of the system, appear as “fragile.” For instance, the binding energy of the deuteron is BE,d = 2.2 MeV Tchem, Tkin. The elastic cross section driving deuteron spectra to kinetic equilibration in central heavy-ion collisions [19] is smaller than the breakup cross section [15,16,17,18] (Anti-) nuclei produced at chemical freeze-out are not expected to survive the hadronic phase, yet their measured production is consistent with statistical-thermal model predictions and a nonzero elliptic flow is observed [19,20]. As 4Li is not stable with respect to strong decay, its measurement is experimentally difficult and probably less constraining than the systematic measurement of the (hyper-)nuclei coalescence parameters proposed here
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