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

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.

scholarly journals Possible signals of two QCD phase transitions at NICA-FAIR energies

2019 ◽  
Vol 204 ◽  
pp. 03001 ◽  
Author(s):  
K. A. Bugaev ◽  
A. I. Ivanytskyi ◽  
V. V. Sagun ◽  
B. E. Grinyuk ◽  
D. O. Savchenko ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Phase Transitions ◽  
Collision Energy ◽  
Center Of Mass ◽  
Solvable Model ◽  
Exactly Solvable Model ◽  
Qcd Phase Diagram ◽  
Exactly Solvable ◽  
Experimental Findings ◽  
Chemical Freeze

The chemical freeze-out irregularities found with the most advanced hadron resonance gas model and possible signals of two QCD phase transitions are discussed. We have found that the center-of-mass collision energy range of tricritical endpoint of QCD phase diagram is [9; 9.2] GeV which is consistent both with the QCD inspired exactly solvable model and experimental findings.

Freeze-out scenarios in small systems at RHIC and LHC energies

2020 ◽  
Vol 29 (02) ◽  
pp. 2050006
Author(s):  
Susil Kumar Panda ◽  
Subhasis Samanta ◽  
Ajay Kumar Dash ◽  
Ranbir Singh ◽  
Rita Paikaray ◽  
...  
Keyword(s):  
System Size ◽  
Particle Multiplicity ◽  
Charged Particle Multiplicity ◽  
Suppression Factor ◽  
Increase With Increase ◽  
Multiplicity Formula ◽  
Charge Multiplicity ◽  
System Volume ◽  
Chemical Freeze ◽  
Freeze Out

We study the hadronic yields produced in two small collision systems [Formula: see text] at [Formula: see text][Formula: see text]TeV and [Formula: see text] at [Formula: see text][Formula: see text]TeV, and extracted the chemical freeze-out (CFO) parameters. The CFO parameters are obtained using a hadron resonance gas (HRG) model and in this study present the system size dependence of the parameters. We observe that with the strangeness suppression factor [Formula: see text] included in the model, a single freeze-out scenario can describe hadronic yields for all the centralities of [Formula: see text] collision at [Formula: see text][Formula: see text]TeV, indicating that the strange hadrons have not reached full equilibrium. On the other hand, for small average charged particle multiplicity ([Formula: see text]) bins of [Formula: see text] collision at [Formula: see text][Formula: see text]TeV strangeness is not fully equilibrated whereas strangeness equilibration seems to be reached in large [Formula: see text]. For both the collision systems, no significant system volume dependence of the temperature has been observed. However, in comparable [Formula: see text] values, temperatures are 10–20[Formula: see text]MeV larger for [Formula: see text] collision compared to [Formula: see text] collision. We observe that the volume of the system at the CFO increases with increase of charge multiplicity for both the collisions. The increase is much steeper in [Formula: see text] collision at [Formula: see text][Formula: see text]TeV than [Formula: see text] collision at [Formula: see text][Formula: see text]TeV. Further, we analyze the transverse momentum ([Formula: see text]) spectra of different hadrons produced in [Formula: see text] collision at [Formula: see text][Formula: see text]TeV in a combined freeze-out scenario. We show the [Formula: see text] dependence of freeze-out parameters. It is observed that with [Formula: see text] included in the model, a single freeze-out scheme can describe the [Formula: see text] spectra. For similar [Formula: see text] values, [Formula: see text] in both the collision systems are close to each other and overall values of [Formula: see text] increase with increase of [Formula: see text]. Unlike CFO scenario using the produced hadron yields only, freeze-out temperature in combined scenario of chemical and kinetic freeze-out, obtained from [Formula: see text] spectra, increases with increase of [Formula: see text]. For smaller [Formula: see text] values, the temperature in [Formula: see text] collision at [Formula: see text][Formula: see text]TeV is similar to that of [Formula: see text] collision at [Formula: see text][Formula: see text]TeV. However, temperatures are larger in [Formula: see text] collision than [Formula: see text] collision at larger [Formula: see text] values.

scholarly journals Chemical freeze-out of strange particles and possible root of strangeness suppression

2013 ◽  
Vol 104 (2) ◽  
pp. 22002 ◽  
Author(s):  
K. A. Bugaev ◽  
D. R. Oliinychenko ◽  
J. Cleymans ◽  
A. I. Ivanytskyi ◽  
I. N. Mishustin ◽  
...  
Keyword(s):  
Strange Particles ◽  
Chemical Freeze ◽  
Freeze Out

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

2020 ◽  
pp. 2040009
Author(s):  
Boris E. Grinyuk ◽  
Kyrill A. Bugaev ◽  
Violetta V. Sagun ◽  
Oleksii I. Ivanytskyi ◽  
Dmitry L. Borisyuk ◽  
...  
Keyword(s):  
Surface Tension ◽  
Center Of Mass ◽  
Hard Core ◽  
Heavy Ion ◽  
Light Nuclei ◽  
Excluded Volume ◽  
Core Radius ◽  
Alice Collaboration ◽  
Chemical Freeze ◽  
Freeze Out

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.

scholarly journals Numerical solutions to Giovannini’s parton branching equation up to TeV energies at the LHC

2020 ◽  
Vol 35 (39) ◽  
pp. 2050325
Author(s):  
Z. Ong ◽  
P. Agarwal ◽  
H. W. Ang ◽  
A. H. Chan ◽  
C. H. Oh
Keyword(s):  
Collision Energy ◽  
Multiplicity Distribution ◽  
Numerical Solutions ◽  
Center Of Mass ◽  
Charged Hadron ◽  
Mass Energy ◽  
Center Of Mass Energy ◽  
Hadron Multiplicity ◽  
Runge Kutta Method ◽  
Hadronic Collisions

The full Giovannini parton branching equation is integrated numerically using the fourth-order Runge-Kutta method. Using a simple hadronization model, a charged-hadron multiplicity distribution is obtained. This model is then fitted to various experimental data up to the TeV scale to study how the Giovannini parameters vary with collision energy and type. The model is able to describe hadronic collisions up to the TeV scale and reveals the emergence of gluonic activity as the center-of-mass energy increases. A prediction is made for [Formula: see text].

scholarly journals Resolving the hyper-triton yield description puzzle in high energy nuclear collisions

2021 ◽  
Vol 57 (2) ◽  
Author(s):  
O. V. Vitiuk ◽  
K. A. Bugaev ◽  
E. S. Zherebtsova ◽  
D. B. Blaschke ◽  
L. V. Bravina ◽  
...  
Keyword(s):  
Collision Energy ◽  
Hard Core ◽  
Star Collaboration ◽  
High Energy ◽  
Nuclear Collisions ◽  
Cluster Data ◽  
New Strategy ◽  
Nuclear Cluster ◽  
Chemical Freeze ◽  
Freeze Out

AbstractThe recently developed hadron resonance gas model with multicomponent hard-core repulsion is used to address and resolve the long standing problem to describe the light nuclear cluster multiplicities including the hyper-triton measured by the STAR Collaboration, known as the hyper-triton chemical freeze-out puzzle. An improved description for the hadronic and light nuclear cluster data measured by STAR at the collision energy $$\sqrt{s_{NN}} =200$$ s NN = 200 GeV and by ALICE at $$\sqrt{s_{NN}} =2.76$$ s NN = 2.76 TeV is obtained. This is achieved by applying a new strategy of analyzing the light nuclear cluster data and by using the value for the hard-core radius of the (anti-)$$\varLambda $$ Λ hyperons found in earlier work. One of the most striking results of the present work is that for the most probable scenario of chemical freeze-out for the STAR energy the obtained parameters allow to simultaneously reproduce the values of the experimental ratios $$S_3$$ S 3 and $${\overline{S}}_3$$ S ¯ 3 which were not included in the fit.

scholarly journals Separate Chemical Freeze-Out of Strange Particles with Conservation Laws

2014 ◽  
Vol 59 (11) ◽  
pp. 1051-1059 ◽  
Author(s):  
D.R. Oliinychenko ◽  
◽  
V.V. Sagun ◽  
A.I. Ivanytskyi ◽  
K.A. Bugaev ◽  
...  
Keyword(s):  
Conservation Laws ◽  
Strange Particles ◽  
Chemical Freeze ◽  
Freeze Out

scholarly journals Hyperbolic Center of Mass for a System of Particles in a Two-Dimensional Space with Constant Negative Curvature: An Application to the Curved 2-Body Problem

Mathematics ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 531
Author(s):  
Pedro Pablo Ortega Palencia ◽  
Ruben Dario Ortiz Ortiz ◽  
Ana Magnolia Marin Ramirez
Keyword(s):  
Negative Curvature ◽  
Dimensional Space ◽  
Center Of Mass ◽  
Simple Expression ◽  
Two Dimensional ◽  
Constant Negative Curvature ◽  
Euclidean Case ◽  
System Of Particles ◽  
Material Points ◽  
The One

In this article, a simple expression for the center of mass of a system of material points in a two-dimensional surface of Gaussian constant negative curvature is given. By using the basic techniques of geometry, we obtained an expression in intrinsic coordinates, and we showed how this extends the definition for the Euclidean case. The argument is constructive and serves to define the center of mass of a system of particles on the one-dimensional hyperbolic sphere LR1.

THE STEREODYNAMICS STUDY OF THE C(3P) + OH (X2 Π) → CO(X1Σ+) + H(2S) REACTION

2010 ◽  
Vol 09 (05) ◽  
pp. 935-943 ◽  
Author(s):  
PENG SONG ◽  
YONG-HUA ZHU ◽  
JIAN-YONG LIU ◽  
FENG-CAI MA
Keyword(s):  
Angular Momentum ◽  
Cross Sections ◽  
Collision Energy ◽  
Energy Surface ◽  
Center Of Mass ◽  
Title Reaction ◽  
High Collision Energy ◽  
Dependency Relationship ◽  
Energy Dependency ◽  
Mass Frame

The stereodynamics of the title reaction on the ground electronic state X2A' potential energy surface (PES)1 has been studied using the quasiclassical trajectory (QCT) method. The commonly used polarization-dependent differential cross-sections (PDDCSs) of the product and the angular momentum alignment distribution, P(θr) and P(Φr), are generated in the center-of-mass frame using QCT method to gain insight of the alignment and orientation of the product molecules. Influence of collision energy on the stereodynamics is shown and discussed. The results reveal that the distribution of P(θr) and P(Φr) is sensitive to collision energy. The PDDCSs exhibit different collision energy dependency relationship at low and high collision energy ranges.

ENHANCING ADEQUACY OF GRADING STUDY PROJECTS ON THE BASE OF PARAMETRIC RELAXATION OF PAIRWISE COMPARISONS

2021 ◽  
Vol 1 ◽  
pp. 122-133
Author(s):  
Alexey V. Oletsky ◽  
◽  
Mikhail F. Makhno ◽  
◽  
Keyword(s):  
Center Of Mass ◽  
Estimation Algorithm ◽  
Relaxation Parameter ◽  
Connected Components ◽  
Pairwise Comparisons ◽  
Strongly Connected Components ◽  
Standard Scale ◽  
Relaxation Parameters ◽  
Strongly Connected ◽  
The One

A problem of automated assessing of students’ study projects is regarded. A heuristic algorithm based on fuzzy estimating of projects and on pairwise comparisons among them is proposed. For improving adequacy and naturalness of grades, an approach based on introducing a parameter named relaxation parameter was suggested in the paper. This enables to reduce the spread between maximum and minimum values of projects in comparison with the one in the standard scale suggested by T. Saati. Reasonable values of this parameter were selected experimentally. For estimating the best alternative, a center of mass of a fuzzy max-min composition should be calculated. An estimation algorithm for a case of non-transitive preferences based on getting strongly connected components and on pairwise comparisons between them is also suggested. In this case, relaxation parameters should be chosen separately for each subtask. So the combined technique of evaluating alternatives proposed in the paper depends of the following parameters: relaxation parameters for pairwise comparisons matrices within each strongly connected components; relaxation parameter for pairwise comparisons matrices among strongly connected components; membership function for describing the best alternative.

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