Classical excluded volume of loosely bound light (anti) nuclei and their chemical freeze-out in heavy ion collisions

From the analysis of light (anti)nuclei multiplicities that were measured recently by the ALICE collaboration in Pb+Pb collisions at the center-of-mass collision energy [Formula: see text][Formula: see text]TeV, there arose a highly nontrivial question about the excluded volume of composite particles. Surprisingly, the hadron resonance gas model (HRGM) is able to perfectly describe the light (anti) nuclei multiplicities under various assumptions. Thus, one can consider the (anti)nuclei with a vanishing hard-core radius (as the point-like particles) or with the hard-core radius of proton, but the fit quality is the same for these assumptions. It is clear, however, that such assumptions are unphysical. Hence we obtain a formula for the classical excluded volume of loosely bound light nuclei consisting of A baryons. To implement a new formula into the HRGM, we have to modify the induced surface tension concept to treat the hadrons and (anti)nuclei on the same footing. We perform a thorough analysis of hadronic and (anti)nuclei multiplicities measured by the ALICE collaboration. The HRGM with the induced surface tension allows us to verify different assumptions on the values of hard-core radii and different scenarios of chemical freeze-out of (anti)nuclei. It is shown that the unprecedentedly high quality of fit [Formula: see text] is achieved, if the chemical freeze-out temperature of hadrons is about [Formula: see text][Formula: see text]MeV, while the one for all (anti)nuclei is [Formula: see text][Formula: see text]MeV.

Download Full-text

Combined analysis of midrapidity transverse momentum spectra of the charged pions and kaons, protons and antiprotons in p+p and Pb+Pb collisions at (snn)1/2 = 2.76 and 5.02 TeV at the LHC

Modern Physics Letters A ◽

10.1142/s0217732320502375 ◽

2020 ◽

Vol 35 (29) ◽

pp. 2050237

Author(s):

Khusniddin K. Olimov ◽

Shakhnoza Z. Kanokova ◽

Alisher K. Olimov ◽

Kobil I. Umarov ◽

Boburbek J. Tukhtaev ◽

...

Keyword(s):

Transverse Momentum ◽

Center Of Mass ◽

Heavy Ion ◽

Transverse Flow ◽

Alice Collaboration ◽

Momentum Spectra ◽

Charged Pions ◽

Transverse Momentum Spectra ◽

Tsallis Distribution ◽

Freeze Out

The experimental transverse momentum spectra of the charged pions and kaons, protons and antiprotons, produced at midrapidity in [Formula: see text] collisions at [Formula: see text] and 5.02 TeV, central (0–5%) and peripheral (60–80%) Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] TeV, central (0–5%), semicentral (40–50%) and peripheral (80–90%) Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] TeV, measured by ALICE collaboration, were analyzed using the Tsallis distribution function as well as Hagedorn formula with the embedded transverse flow. To exclude the influence (on the results) of different available fitting [Formula: see text] ranges in the analyzed collisions, we compare the results obtained from combined (simultaneous) fits of midrapidity spectra of the charged pions and kaons, protons and antiprotons with the above theoretical model functions using the identical fitting [Formula: see text] ranges in [Formula: see text] as well as Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] and 5.02 TeV. Using the combined fits with the thermodynamically consistent Tsallis distribution as well as the simple Tsallis distribution without thermodynamical description, it is obtained that the global temperature [Formula: see text] and non-extensivity parameter [Formula: see text] slightly increase (consistently for all the particle types) with an increase in center-of-mass (c.m.) energy [Formula: see text] of [Formula: see text] collisions from 2.76 TeV to 5.02 TeV, indicating that the more violent and faster [Formula: see text] collisions at [Formula: see text] TeV result in a smaller degree of thermalization (higher degree of non-equilibrium) compared to that in [Formula: see text] collisions at [Formula: see text] TeV. The [Formula: see text] values for pions and kaons proved to be very close to each other, whereas [Formula: see text] for protons and antiprotons proved to be significantly lower than that for pions and kaons, that is [Formula: see text]. The results of the combined fits using Hagedorn formula with the embedded transverse flow are consistent with practically no (zero) transverse (radial) flow in [Formula: see text] collisions at [Formula: see text] and 5.02 TeV. Using Hagedorn formula with the embedded transverse flow, it is obtained that the value of the (average) transverse flow velocity increases and the temperature [Formula: see text] decreases with an increase in collision centrality in Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] and 5.02 TeV, which is in good agreement with the results of the combined Boltzmann–Gibbs blast-wave fits to the particle spectra in Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] and 5.02 TeV in recent works of ALICE collaboration. The temperature [Formula: see text] parameter, which approximates the kinetic freeze-out temperature, was shown to coincide in central (0–5%) Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] and 5.02 TeV, which implies, taking into account the results of our previous analysis, that kinetic freeze-out temperature stays practically constant in central heavy-ion collisions in [Formula: see text] GeV energy range.

Download Full-text

Production of light nuclei in heavy ion collisions via hagedorn resonances

The European Physical Journal A ◽

10.1140/epja/s10050-020-00329-z ◽

2021 ◽

Vol 57 (2) ◽

Author(s):

K. Gallmeister ◽

C. Greiner

Keyword(s):

Experimental Data ◽

Heavy Ion Collisions ◽

Heavy Ion ◽

Decay Rates ◽

Binding Energies ◽

Light Nuclei ◽

Saha Equation ◽

Ion Collisions ◽

Chemical Freeze ◽

Freeze Out

AbstractThe physical processes behind the production of light nuclei in heavy ion collisions are unclear. The successful theoretical description of experimental yields by thermal models conflicts with the very small binding energies of the observed states, being fragile in such a hot and dense environment. Other available ideas are delayed production via coalescence, or a cooling of the system after the chemical freeze-out according to a Saha equation, or a ‘quench’ instead of a thermal freeze-out. A recently derived prescription of an (interacting) Hagedorn gas is applied to consolidate the above pictures. The tabulation of decay rates of Hagedorn states into light nuclei allows to calculate yields usually inaccessible due to very poor Monte Carlo statistics. Decay yields of stable hadrons and light nuclei are calculated. While the scale-free decays of Hagedorn states alone are not compatible with the experimental data, a thermalized hadron and Hagedorn state gas is able to describe the experimental data. Applying a cooling of the system according to a Saha-equation with conservation of nucleon and anti-nucleon numbers leads to (nearly) temperature independent yields, thus a production of the light nuclei at temperatures much lower than the chemical freeze-out temperature is compatible with experimental data and with the statistical hadronization model.

Download Full-text

Freeze-Out Parameters in Heavy-Ion Collisions at AGS, SPS, RHIC, and LHC Energies

Advances in High Energy Physics ◽

10.1155/2015/349013 ◽

2015 ◽

Vol 2015 ◽

pp. 1-20 ◽

Cited By ~ 53

Author(s):

Sandeep Chatterjee ◽

Sabita Das ◽

Lokesh Kumar ◽

D. Mishra ◽

Bedangadas Mohanty ◽

...

Keyword(s):

Transverse Momentum ◽

Heavy Ion Collisions ◽

Heavy Ion ◽

High Energy ◽

Particle Multiplicity ◽

Charged Particle Multiplicity ◽

Ion Collisions ◽

Momentum Distributions ◽

Chemical Freeze ◽

Freeze Out

We review the chemical and kinetic freeze-out conditions in high energy heavy-ion collisions for AGS, SPS, RHIC, and LHC energies. Chemical freeze-out parameters are obtained using produced particle yields in central collisions while the corresponding kinetic freeze-out parameters are obtained using transverse momentum distributions of produced particles. For chemical freeze-out, different freeze-out scenarios are discussed such as single and double/flavor dependent freeze-out surfaces. Kinetic freeze-out parameters are obtained by doing hydrodynamic inspired blast wave fit to the transverse momentum distributions. The beam energy and centrality dependence of transverse energy per charged particle multiplicity are studied to address the constant energy per particle freeze-out criteria in heavy-ion collisions.

Download Full-text

Centrality Dependence of Chemical Freeze-Out Parameters and Strangeness Equilibration in RHIC and LHC Energies

Advances in High Energy Physics ◽

10.1155/2021/6611394 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Deeptak Biswas

Keyword(s):

Hadron Collider ◽

Heavy Ion ◽

Strange Particle ◽

Relativistic Heavy Ion Collider ◽

Yield Data ◽

Central Collisions ◽

Chemical Potentials ◽

Beam Energy Scan ◽

Chemical Freeze ◽

Freeze Out

We have estimated centrality variation of chemical freeze-out parameters from yield data at midrapidity of π ± , K ± and p , p ¯ for collision energies of RHIC (Relativistic Heavy Ion Collider), Beam Energy Scan (RHIC-BES) program, and LHC (Large Hadron Collider). We have considered a simple hadron resonance gas model and employed a formalism involving conserved charges ( B , Q , S ) of QCD for parameterization. Along with temperature and three chemical potentials ( T , μ B , μ Q , μ S ), a strangeness undersaturation factor ( γ S ) has been used to incorporate the partial equilibration in the strange sector. Our obtained freeze-out temperature does not vary much with centrality, whereas chemical potentials and γ S seem to have a significant dependence. The strange hadrons are found to deviate from a complete chemical equilibrium at freeze-out at the peripheral collisions. This deviation appears to be more prominent as the collision energy decreases at lower RHIC-BES energies. We have also shown that this departure from equilibrium reduces towards central collisions, and strange particle equilibration may happen after a threshold number of participants in A - A collision.

Download Full-text

Hard-Core Radius of Nucleons within the Induced Surface Tension Approach

Universe ◽

10.3390/universe5020063 ◽

2019 ◽

Vol 5 (2) ◽

pp. 63 ◽

Cited By ~ 6

Author(s):

Kyrill Bugaev ◽

Aleksei Ivanytskyi ◽

Violetta Sagun ◽

Boris Grinyuk ◽

Denis Savchenko ◽

...

Keyword(s):

Surface Tension ◽

Nuclear Matter ◽

Equations Of State ◽

Hard Core ◽

Blocking Effect ◽

Composite Particles ◽

Core Radius ◽

Pauli Blocking ◽

Novel Approach ◽

Recent Approach

We review the recent approach to model the hadronic and nuclear matter equations of state using the induced surface tension concept, which allows one to go far beyond the usual Van der Waals approximation. Since the obtained equations of state, classical and quantum, are among the most successful ones in describing the properties of low density phases of strongly interacting matter, they set strong restrictions on the possible value of the hard-core radius of nucleons, which is widely used in phenomenological equations of state. We summarize the latest results obtained within this novel approach and perform a new detailed analysis of the hard-core radius of nucleons, which follows from hadronic and nuclear matter properties. Such an analysis allows us to find the most trustworthy range of its values: the hard-core radius of nucleons is 0.3–0.36 fm. A comparison with the phenomenology of neutron stars implies that the hard-core radius of nucleons has to be temperature and density dependent. Such a finding is supported when the eigenvolume of composite particles like hadrons originates from their fermionic substructure due to the Pauli blocking effect.

Download Full-text

Separate freeze-out of strange particles and the quark-hadron phase transition

EPJ Web of Conferences ◽

10.1051/epjconf/201818202057 ◽

2018 ◽

Vol 182 ◽

pp. 02057

Author(s):

K. Bugaev ◽

V. Sagun ◽

A. Ivanytskyi ◽

E. Nikonov ◽

J. Cleymans ◽

...

Keyword(s):

Collision Energy ◽

Center Of Mass ◽

Suppression Factor ◽

Hadron Phase ◽

Hadron Multiplicity ◽

Strange Particles ◽

The One ◽

Baryonic Charge ◽

Chemical Freeze ◽

Freeze Out

The scenario of the independent chemical freeze-outs for strange and nonstrange particles is discussed. Within such a scenario an apparent in-equilibrium of strangeness is naturally explained by a separation of chemical freeze-out of strange hadrons from the one of non-strange hadrons, which, nevertheless, are connected by the conservation laws of entropy, baryonic charge and third isospin projection. An interplay between the separate freeze-out of strangeness and its residual non-equilibrium is studied within an elaborate version of the hadron resonance gas model. The developed model enables us to perform a high-quality fit of the hadron multiplicity ratios measured at AGS, SPS and RHIC with an overall fit quality ϰ2/dof = 0:93. A special attention is paid to a description of the Strangeness Horn and to the well-known problem of selective suppression of Δ- and ж hyperons. It is remarkable that for all collision energies the strangeness suppression factor γs is about 1 within the error bars. The only exception is found in the vicinity of the center-of-mass collision energy 7.6 GeV, at which a residual enhancement of strangeness of about 20 % is observed.

Download Full-text