Light Cluster Production in Central Symmetric Heavy-Ion Reactions from Fermi to Gev Energies

Correlations and clustering are of great importance in the study of the Nuclear Equation of State. Information on these items/aspects can be obtained using heavy-ion reactions which are described by dynamical theories. We propose a dataset that will be useful for improving the description of light cluster production in transport model approaches. The dataset combines published and new data and is presented in a form that allows direct comparison of the experiment with theoretical predictions. The dataset is ranging in bombarding energy from 32 to 1930 A MeV. In constructing this dataset, we put in evidence the existence of a change in the light cluster production mechanism that corresponds to a peak in deuteron production.

The nature of X(3872) from high-multiplicity pp collisions

The structure of exotic resonances that do not trivially fit the usual quark model expectations has been a matter of intense scientific debate during the last two decades. A possible way of estimating the size of these states is to study their behavior when immersed in QCD matter. Recently, LHCb has measured the relative abundance of the exotic $$X(3872)$$ X ( 3872 ) over the ordinary $$\psi (2S)$$ ψ ( 2 S ) . We use the comover interaction model to study the yield of a compact $$X(3872)$$ X ( 3872 ) . To confirm the reliability of the model in high-multiplicity pp collisions, we describe the suppression of excited over ground $$\Upsilon $$ Υ states. With this at hand, we show that the size of the compact $$X(3872)$$ X ( 3872 ) would be slightly larger than that of the $$\psi (2S)$$ ψ ( 2 S ) . If the $$X(3872)$$ X ( 3872 ) is instead assumed to be a meson molecule of large size, we argue that its evolution in QCD matter should be described via a coalescence model, as suggested by data on deuteron production. We show that the predictions of this model for the $$X(3872)$$ X ( 3872 ) are in contrast with data.

Understanding the energy dependence of $$B_2$$ in heavy ion collisions: interplay of volume and space-momentum correlations

The deuteron coalescence parameter $$B_2$$ B 2 in proton+proton and nucleus+nucleus collisions in the energy range of $$\sqrt{s_{NN}}=$$ s NN = 900–7000 GeV for proton + proton and $$\sqrt{s_{NN}}=$$ s NN = 2–2760 GeV for nucleus + nucleus collisions is analyzed with the Ultrarelativistic Quantum Molecular Dynamics (UrQMD) transport model, supplemented by an event-by-event phase space coalescence model for deuteron and anti-deuteron production. The results are compared to data by the E866, E877, PHENIX, STAR and ALICE experiments. The $$B_2$$ B 2 values are calculated from the final spectra of protons and deuterons. At lower energies, $$\sqrt{s_{NN}}\le 20$$ s NN ≤ 20 GeV, $$B_2$$ B 2 drops drastically with increasing energy. The calculations confirm that this is due to the increasing freeze-out volume reflected in $$B_2\sim 1/V$$ B 2 ∼ 1 / V . At higher energies, $$\sqrt{s_{NN}}\ge 20$$ s NN ≥ 20 GeV, $$B_2$$ B 2 saturates at a constant level. This qualitative change and the vanishing of the volume suppression is shown to be due to the development of strong radial flow with increasing energy. The flow leads to strong space-momentum correlations which counteract the volume effect.

(Anti-)deuteron production in pp collisions at $$\sqrt{s}=13 \ \text {TeV}$$

The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper the production of $$\text {(anti-)deuterons}$$ (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at $$\sqrt{s}=13$$ s = 13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity ($${\mathrm {d} N_{ch}/\mathrm {d} \eta } \sim 26$$ d N ch / d η ∼ 26 ) as measured in p–Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p–Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM).