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Editorial

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7 pages, 2658 KiB

Open AccessEditorial

Jean Cleymans: Scientist, Mentor, and Friend Extraordinaire

by Dinesh Kumar Srivastava

Physics 2022, 4(3), 690-696; https://doi.org/10.3390/physics4030047 - 22 Jun 2022

Viewed by 1727

Abstract

When in 1988, I decided to start working on the physics of quark-gluon plasma and relativistic heavy-ion collisions, I was reasonably well-entrenched in my chosen field of low-energy nuclear reactions and break-up of light nuclei, having worked for over 17 years in that [...] Read more.

When in 1988, I decided to start working on the physics of quark-gluon plasma and relativistic heavy-ion collisions, I was reasonably well-entrenched in my chosen field of low-energy nuclear reactions and break-up of light nuclei, having worked for over 17 years in that field [...] Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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Research

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26 pages, 1906 KiB

Open AccessEditor’s ChoiceArticle

Emergent Flow Signal and the Colour String Fusion

by Daria Prokhorova and Evgeny Andronov

Physics 2024, 6(1), 264-289; https://doi.org/10.3390/physics6010019 - 20 Feb 2024

Viewed by 385

Abstract

In this study, we develop the colour string model of particle production, based on the multi-pomeron exchange scenario, to address the controversial origin of the flow signal measured in proton–proton inelastic interactions. Our approach takes into account the string–string interactions but does not [...] Read more.

In this study, we develop the colour string model of particle production, based on the multi-pomeron exchange scenario, to address the controversial origin of the flow signal measured in proton–proton inelastic interactions. Our approach takes into account the string–string interactions but does not include a hydrodynamic phase. We consider a comprehensive three-dimensional dynamics of strings that leads to the formation of strongly heterogeneous string density in an event. The latter serves as a source of particle creation. The string fusion mechanism, which is a major feature of the model, modifies the particle production and creates azimuthal anisotropy. Model parameters are fixed by comparing the model distributions with the ATLAS experiment proton–proton data at the centre-of-mass energy

\sqrt{s} = 13

TeV. The results obtained for the two-particle angular correlation function,

C (Δ η, Δ ϕ)

, with

Δ η

and

Δ ϕ

differences in, respectively, pseudorapidities and azimuthal angles between two particles, reveal the resonance contributions and the near-side ridge. Model calculations of the two-particle cumulants,

c_{2} {2}

, and second order flow harmonic,

v_{2} {2}

, also performed using the two-subevent method, are in qualitative agreement with the data. The observed absence of the away-side ridge in the model results is interpreted as an imperfection in the definition of the time for the transverse evolution of the string system. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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8 pages, 378 KiB

Open AccessArticle

The Abundance of the Species

by Helmut Satz

Physics 2022, 4(3), 912-919; https://doi.org/10.3390/physics4030059 - 19 Aug 2022

Viewed by 1231

Abstract

I review the pioneering work of Jean Cleymans in establishing the statistical description of multihadron production in high energy strong interaction physics. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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7 pages, 234 KiB

Open AccessArticle

Jean Cleymans, Stringy Thermal Model, Tsallis Quantum Statistics

by Tamás S. Biró

Physics 2022, 4(3), 873-879; https://doi.org/10.3390/physics4030056 - 2 Aug 2022

Viewed by 1278

Abstract

My memories on Jean Cleymans and a brief advocation of the stringy thermal model, describing massless constituents with the energy-per-particle and temperature relation,

E / N = 6 T = 1

GeV, are presented. Another topic, the Kubo–Martin–Schwinger (KMS) relation applied to the [...] Read more.

My memories on Jean Cleymans and a brief advocation of the stringy thermal model, describing massless constituents with the energy-per-particle and temperature relation,

E / N = 6 T = 1

GeV, are presented. Another topic, the Kubo–Martin–Schwinger (KMS) relation applied to the Tsallis distribution in quantum statistics is also sketched, which was triggered by our discussions with Jean. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

12 pages, 324 KiB

Open AccessArticle

Analytical Calculations of the Quantum Tsallis Thermodynamic Variables

by Ayman Hussein and Trambak Bhattacharyya

Physics 2022, 4(3), 800-811; https://doi.org/10.3390/physics4030051 - 19 Jul 2022

Cited by 1 | Viewed by 1833

Abstract

In this paper, we provide an account of analytical results related to the Tsallis thermodynamics that have been the subject matter of a lot of studies in the field of high-energy collisions. After reviewing the results for the classical case in the massless [...] Read more.

In this paper, we provide an account of analytical results related to the Tsallis thermodynamics that have been the subject matter of a lot of studies in the field of high-energy collisions. After reviewing the results for the classical case in the massless limit and for arbitrarily massive classical particles, we compute the quantum thermodynamic variables. For the first time, the analytical formula for the pressure of a Tsallis-like gas of massive bosons has been obtained. The study serves both as a brief review of the knowledge gathered in this area, and as original research that forwards the existing scholarship. The results of the present paper will be important in a plethora of studies in the field of high-energy collisions including the propagation of non-linear waves generated by the traversal of high-energy particles inside the quark-gluon plasma medium showing the features of non-extensivity. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

13 pages, 403 KiB

Open AccessArticle

Nuclear Modification Factor in Small System Collisions within Perturbative QCD including Thermal Effects

by Lucas Moriggi and Magno Machado

Physics 2022, 4(3), 787-799; https://doi.org/10.3390/physics4030050 - 18 Jul 2022

Cited by 2 | Viewed by 2015

Abstract

In this paper, the nuclear modification factors,

R_{x A}

, are investigated for pion production in small system collisions, measured by PHENIX experiment at RHIC (Relativistic Heavy Ion Collider). The theoretical framework is the parton transverse momentum

k_{T}

-factorization formalism for [...] Read more.

In this paper, the nuclear modification factors,

R_{x A}

, are investigated for pion production in small system collisions, measured by PHENIX experiment at RHIC (Relativistic Heavy Ion Collider). The theoretical framework is the parton transverse momentum

k_{T}

-factorization formalism for hard processes at small momentum fraction, x. Evidence for collective expansion and thermal effects for pions, produced at equilibrium, is studied based on phenomenological parametrization of blast-wave type in the relaxation time approximation. The dependencies on the centrality and on the projectile species are discussed in terms of the behavior of Cronin peak and the suppression of

R_{x A}

at large transverse momentum,

p_{T}

. The multiplicity of produced particles, which is sensitive to the soft sector of the spectra, is also included in the present analysis. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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13 pages, 568 KiB

Open AccessArticle

Nonextensive Statistics in High Energy Collisions

by Lucas Q. Rocha, Eugenio Megías, Luis A. Trevisan, Khusniddin K. Olimov, Fuhu Liu and Airton Deppman

Physics 2022, 4(2), 659-671; https://doi.org/10.3390/physics4020044 - 9 Jun 2022

Cited by 4 | Viewed by 1991

Abstract

The present paper reports on the methods of the systematic analysis of the high-energy collision distributions—in particular, those adopted by Jean Cleymans. The analysis of data on high-energy collisions, using non-extensive statistics, represents an important part of Jean Cleymans scientific activity in the [...] Read more.

The present paper reports on the methods of the systematic analysis of the high-energy collision distributions—in particular, those adopted by Jean Cleymans. The analysis of data on high-energy collisions, using non-extensive statistics, represents an important part of Jean Cleymans scientific activity in the last decade. The methods of analysis, developed and employed by Cleymans, are discussed and compared with other similar methods. As an example, analyses of a set of the data of proton-proton collisions at the center-of-mass energies,

\sqrt{s} = 0.9

and 7 TeV, are provided applying different methods and the results obtained are discussed. This line of research has the potential to enlarge our understanding of strongly interacting systems and to be continued in the future. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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24 pages, 801 KiB

Open AccessArticle

Enthusiasm and Skepticism: Two Pillars of Science—A Nonextensive Statistics Case

by Constantino Tsallis

Physics 2022, 4(2), 609-632; https://doi.org/10.3390/physics4020041 - 27 May 2022

Cited by 10 | Viewed by 2399

Abstract

Science and its evolution are based on complex epistemological structures. Two of the pillars of such a construction definitively are enthusiasm and skepticism, both being ingredients without which solid knowledge is hardly achieved and certainly not guaranteed. Our friend and colleague Jean Willy [...] Read more.

Science and its evolution are based on complex epistemological structures. Two of the pillars of such a construction definitively are enthusiasm and skepticism, both being ingredients without which solid knowledge is hardly achieved and certainly not guaranteed. Our friend and colleague Jean Willy André Cleymans (1944–2021), with his open personality, high and longstanding interest for innovation, and recognized leadership in high-energy physics, constitutes a beautiful example of the former. Recently, Joseph I. Kapusta has generously and laboriously offered an interesting illustration of the latter pillar, in the very same field of physics, concerning the very same theoretical frame, namely, nonextensive statistical mechanics and the nonadditive q-entropies on which it is based. I present here a detailed analysis, point by point, of Kapusta’s 19 May 2021 talk and, placing the discussion in a sensibly wider and updated perspective, I refute his bold conclusion that indices q have no physical foundation. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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12 pages, 394 KiB

Open AccessArticle

QCD Phase Boundary and the Hadrochemical Horizon

by Berndt Müller

Physics 2022, 4(2), 597-608; https://doi.org/10.3390/physics4020040 - 23 May 2022

Cited by 1 | Viewed by 1495

Abstract

I review the physics of the phase boundary between hadronic matter and quark matter from several different points of view. These include thermodynamics, statistical physics, and chemical kinetics. In particular, the review focuses on the role of the chemical freeze-out line and its [...] Read more.

I review the physics of the phase boundary between hadronic matter and quark matter from several different points of view. These include thermodynamics, statistical physics, and chemical kinetics. In particular, the review focuses on the role of the chemical freeze-out line and its relation to the concept of valence-quark percolation. The review ends with some recollections of Jean Cleymans. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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14 pages, 437 KiB

Open AccessArticle

Jet Transport Coefficient at the Large Hadron Collider Energies in a Color String Percolation Approach

by Aditya Nath Mishra, Dushmanta Sahu and Raghunath Sahoo

Physics 2022, 4(1), 315-328; https://doi.org/10.3390/physics4010022 - 16 Mar 2022

Cited by 5 | Viewed by 2101

Abstract

Within the color string percolation model (CSPM), jet transport coefficient,

\hat{q}

, is calculated for various multiplicity classes in proton-proton and centrality classes in nucleus-nucleus collisions at the Large Hadron Collider energies for a better understanding of the matter formed in ultra-relativistic [...] Read more.

Within the color string percolation model (CSPM), jet transport coefficient,

\hat{q}

, is calculated for various multiplicity classes in proton-proton and centrality classes in nucleus-nucleus collisions at the Large Hadron Collider energies for a better understanding of the matter formed in ultra-relativistic collisions.

\hat{q}

is studied as a function of final state charged particle multiplicity (pseudorapidity density at midrapidity), initial state percolation temperature and energy density. The CSPM results are then compared with different theoretical calculations from the JET Collaboration those incorporate particle energy loss in the medium. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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Review

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16 pages, 472 KiB

Open AccessReview

Probing Relativistic Heavy-Ion Collisions via Photon Anisotropic Flow Ratios. A Brief Review

by Rupa Chatterjee and Pingal Dasgupta

Physics 2024, 6(2), 674-689; https://doi.org/10.3390/physics6020044 - 4 May 2024

Viewed by 327

Abstract

The anisotropic flow of photons produced in relativistic nuclear collisions is known as a promising observable for studying the initial state and the subsequent evolution of the hot and dense medium formed in such collisions. The investigation of photon anisotropic flow coefficients, [...] Read more.

The anisotropic flow of photons produced in relativistic nuclear collisions is known as a promising observable for studying the initial state and the subsequent evolution of the hot and dense medium formed in such collisions. The investigation of photon anisotropic flow coefficients,

v_{n}

, has attracted high interest over the last decade, involving both theory and experiment. The thermal emission of photons and their anisotropic flow are found to be highly sensitive to the initial state of the fireball, where even slight modifications can lead to significant variations in the final state results. In contrast, the ratio of photon anisotropic flow stands out as a robust observable, exhibiting minimal sensitivity to the initial conditions. Here, we briefly review the studies of the individual elliptic and triangular flow parameters of photons as well as their ratios and how these parameters serve as valuable probes for investigating the intricacies of the initial state and addressing the challenges posed by the direct photon puzzle. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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18 pages, 373 KiB

Open AccessReview

Stochastic Variational Method for Viscous Hydrodynamics

by Takeshi Kodama and Tomoi Koide

Physics 2022, 4(3), 847-864; https://doi.org/10.3390/physics4030054 - 26 Jul 2022

Cited by 3 | Viewed by 1646

Abstract

In this short review, we focus on some of the subjects, related to J. Cleymans’ pioneering contribution of statistical approaches to the particle production process in heavy-ion collisions. We discuss these perspectives from the effects of stochastic processes in collective variables of hydrodynamic [...] Read more.

In this short review, we focus on some of the subjects, related to J. Cleymans’ pioneering contribution of statistical approaches to the particle production process in heavy-ion collisions. We discuss these perspectives from the effects of stochastic processes in collective variables of hydrodynamic description, which is described by a stochastic variational method. In this connection, we stress also the necessity of the inclusion of surface and quantum effects in the study of relativistic heavy-ion reactions. Full article

(This article belongs to the Special Issue Jean Cleymans: A Life for Physics)

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