Going beyond the second virial coefficient in the hadron resonance gas model

On separate chemical freeze-outs of hadrons and light (anti)nuclei in high energy nuclear collisions

“…Partly it is inspired by the fact that it looks rather surprising that light nuclei with binding energies of an order of a few MeV are produced at all in such violent collisions. Two main approaches, thermal production model [2,3,4,5,6] and coalescence one [7,8,9,10,11,12] are able to explain this phenomenon equally well. Usually, the thermal model assumes a perfect chemical equilibrium above the chemical freeze-out (CFO) temperature T CF O and a sharp CFO of all hadrons at this temperature.…”

“…Usually, the thermal model assumes a perfect chemical equilibrium above the chemical freeze-out (CFO) temperature T CF O and a sharp CFO of all hadrons at this temperature. After the CFO the yields are assumed to be unchanged, but particles can scatter elastically until the system reaches the moment of kinetic freeze-out, which at the ALICE experiment was reported to occur at temperature about 115 MeV [1], while the corresponding CFO temperature varies found in thermal model varies from 150 [5,6] MeV to 160 MeV [2]. In contrast to these assumptions, the coalescence approach postulates that the light nuclei are formed only at late times of the nuclear-nuclear reaction via the binding of nucleons that move close in phase space.…”

“…Indeed, in light (anti)nuclei the nucleons and hyperons are loosely bound and, hence, the radius of small nuclei of A nucleons, or baryons in general, with 2 ≤ A ≤ 4 is about 1.8-2 fm [13], i.e. it is essentially larger than the maximal double hard-core radius of hadrons (0.84 fm) [5,6] even for a deuteron (A = 2). The total proper volume of A baryons with the hard-core radius R b is…”

“…since each baryon in a nucleus interacts with external particle individually and the other baryons do not affect them due to a very large distance between baryons inside a nucleus. Note that the recently developed hadron resonance gas model (HRGM) which is based on the induced surface tension (IST) concept [5,6,14] belongs to the class of HRGM (see, e.g., [15,16]) which can handle any number of individual hadron excluded volumina corresponding to different hard-core radii (for a discussion and important applications see also [17]). Hence, in this work we report our preliminary results on the analysis of the ALICE hadronic and (anti)nuclei multiplicities measured at the collision energy √ s N N = 2.76 TeV with the hard-core radii of nuclei given by Eq.…”

Tetraneutron condensation in neutron rich matter

“…In particular and as a result, the calculation of the contribution of tetraneutrons to thermodynamic quantities, such as pressure or energy density, is performed in a different fashion than for other non-resonant states due to the inclusion of a mass distribution function ρ 4n (m). This approach has been applied in various versions of the hadron resonance gas model for the description of experimental hadron multiplicities produced in heavy ion collisions [34,35]. Technically, it involves an integration over masses exceeding the dominant decay channel threshold, m th 4n , while ρ 4n (m) gives an integration weight.…”