Research

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7 pages, 3979 KiB

Open AccessArticle

Quark Matter at High Baryon Density, Conformality and Quarkyonic Matter

by Larry McLerran

Symmetry 2023, 15(6), 1150; https://doi.org/10.3390/sym15061150 - 25 May 2023

Viewed by 943

This paper discusses high-baryon-density quarkyonic matter in the context of recent observations concerning neutron stars and the qualitative reasons why quarkyonic matter explains certain features of the equation of state that arises from these observations. The paper then provides a qualitative discussion of [...] Read more.

This paper discusses high-baryon-density quarkyonic matter in the context of recent observations concerning neutron stars and the qualitative reasons why quarkyonic matter explains certain features of the equation of state that arises from these observations. The paper then provides a qualitative discussion of the quarkyonic hypotheses, and the essential features of quarkyonic matter that explain the outstanding features of the equation of state. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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8 pages, 286 KiB

Open AccessArticle

T_cs and

T_{c \bar{s}}

Family Production in Multi-Production Processes

by Chuanhui Jiang, Yi Jin, Shi-Yuan Li, Yan-Rui Liu and Zong-Guo Si

Symmetry 2023, 15(3), 695; https://doi.org/10.3390/sym15030695 - 10 Mar 2023

Cited by 2 | Viewed by 902

Abstract

The production mechanism of multiquark exotic hadrons in high energy multiproduction processes lies in the structure of the relevant exotic hadrons as well as in some important aspects of high energy scattering, such as multi-parton interactions, underlying events, etc. At mass pole around [...] Read more.

The production mechanism of multiquark exotic hadrons in high energy multiproduction processes lies in the structure of the relevant exotic hadrons as well as in some important aspects of high energy scattering, such as multi-parton interactions, underlying events, etc. At mass pole around 2900 MeV, a family of open charm tetraquarks,

T_{c s}

s and

T_{c \bar{s}}

s, are observed in B decay. They are also suitable for study in multiproduction processes to obtain more information on their structure. If these resonances are produced as compact four-quark states, one can predict the production properties based on the similarities in their production mechanism to those of

Ξ_{c}

,

Σ_{c}

, and

Λ_{c}

. Physics implies that the colour and baryon number fluctuations of the preconfinement system in high energy scattering can enhance both the baryon and four-quark state production rates via ‘diquark fragmentation’. We calculate the production properties of the tetraquark family

T_{c s}

s and

T_{c \bar{s}}

s at LHC energy for the forthcoming LHC measurements. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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14 pages, 671 KiB

Open AccessArticle

QCD Matter and Phase Transitions under Extreme Conditions

by Mei Huang and Pengfei Zhuang

Symmetry 2023, 15(2), 541; https://doi.org/10.3390/sym15020541 - 17 Feb 2023

Cited by 3 | Viewed by 1650

Abstract

The interplay of chiral dynamics and gluodynamics plays an essential role in the nonperturbative QCD region, and the chiral phase transition and deconfinement phase transition are the main topics of QCD phase transitions under extreme conditions, e.g., finite temperature and/or baryon density, strong [...] Read more.

The interplay of chiral dynamics and gluodynamics plays an essential role in the nonperturbative QCD region, and the chiral phase transition and deconfinement phase transition are the main topics of QCD phase transitions under extreme conditions, e.g., finite temperature and/or baryon density, strong magnetic fields, and fast rotation. We briefly introduce our own recent progress from the theoretical side on QCD phase transitions and phase diagrams under extreme conditions related to the early universe, compact stars, and heavy-ion collisions. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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14 pages, 1040 KiB

Open AccessArticle

The Metastable State and the Finite-Size Effect of the First-Order Phase Transition

by Mingmei Xu and Yuanfang Wu

Symmetry 2023, 15(2), 510; https://doi.org/10.3390/sym15020510 - 14 Feb 2023

Viewed by 1065

Abstract

In the QCD, a transition restoring the chiral symmetry occurs at a high temperature and density. Searching for the signals of the QCD phase transition is one of the goals of the current relativistic heavy-ion physics programs. The metastable state is a unique [...] Read more.

In the QCD, a transition restoring the chiral symmetry occurs at a high temperature and density. Searching for the signals of the QCD phase transition is one of the goals of the current relativistic heavy-ion physics programs. The metastable state is a unique feature of the first-order phase transition. Using the van der Waals equation of state, the role of the metastable state in finite-size effects is analyzed. It is found that the finite-size effects of the first-order phase transition are closely related to the metastable state. Metastability can be observed in the distribution of the order parameters and the probability of its occurrence depends on the system scale. A sizable probability of the metastability requires a small enough system size. The possibility of observing the metastability in the RHIC/BES is discussed. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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20 pages, 905 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Collective Excitation in High-Energy Nuclear Collisions—In Memory of Professor Lianshou Liu

by Huan Zhong Huang, Feng Liu, Xiaofeng Luo, Shusu Shi, Fuqiang Wang and Nu Xu

Symmetry 2023, 15(2), 499; https://doi.org/10.3390/sym15020499 - 13 Feb 2023

Cited by 3 | Viewed by 1366

Abstract

We celebrate the legacies of our friend and mentor Professor Lianshou Liu who was one of the pioneers for the phenomenology of multi-particle interactions and initiated the physics of relativistic heavy-ion collisions in China. In this article, we discuss some of the recent [...] Read more.

We celebrate the legacies of our friend and mentor Professor Lianshou Liu who was one of the pioneers for the phenomenology of multi-particle interactions and initiated the physics of relativistic heavy-ion collisions in China. In this article, we discuss some of the recent exciting experimental observations on the collective phenomena including collectivity, chirality, criticality, strangeness production, and thermal equilibrium in high-energy nuclear collisions. Future directions, especially the physics at high baryon density, will be discussed with a focus on the first-order phase boundary and hyperon–nucleon interactions. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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16 pages, 521 KiB

Open AccessArticle

Production of Strange and Charm Hadrons in Pb+Pb Collisions at

\sqrt{s_{N N}}

= 5.02 TeV

by Wen-Bin Chang, Rui-Qin Wang, Jun Song, Feng-Lan Shao, Qun Wang and Zuo-Tang Liang

Symmetry 2023, 15(2), 400; https://doi.org/10.3390/sym15020400 - 02 Feb 2023

Viewed by 1213

Abstract

Using a quark combination model with the equal-velocity combination approximation, we study the production of hadrons with strangeness and charm flavor quantum numbers in Pb+Pb collisions at

\sqrt{s_{N N}} =

5.02 TeV. We present analytical expressions and numerical results for these hadrons’ [...] Read more.

Using a quark combination model with the equal-velocity combination approximation, we study the production of hadrons with strangeness and charm flavor quantum numbers in Pb+Pb collisions at

\sqrt{s_{N N}} =

5.02 TeV. We present analytical expressions and numerical results for these hadrons’ transverse momentum spectra and yield ratios. Our numerical results agree well with the experimental data available. The features of strange and charm hadron production in the quark–gluon plasma at the early stage of heavy ion collisions are also discussed. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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13 pages, 1247 KiB

Open AccessArticle

On Thermodynamically Consistent Quasiparticle Model at Finite Chemical Potential

by Wei-Liang Qian, Hong-Hao Ma, Shaoyu Yin and Ping Wang

Symmetry 2023, 15(1), 241; https://doi.org/10.3390/sym15010241 - 16 Jan 2023

Viewed by 1375

Abstract

We explore the quasiparticle model at the finite chemical potential related to Ru-Keng Su’s distinguished contributions to the topic. In addition, we discuss the recent developments in the model, and in particular, one argues that the effective mass of the quasiparticle might attain [...] Read more.

We explore the quasiparticle model at the finite chemical potential related to Ru-Keng Su’s distinguished contributions to the topic. In addition, we discuss the recent developments in the model, and in particular, one argues that the effective mass of the quasiparticle might attain a specific form as a function of momentum, in addition to its dependence on the temperature and chemical potential. Unlike the approaches based on the properties of underlying symmetry or the renormalization group, the momentum dependence emerges as a special solution to an integro-differential equation resulting from the underlying thermodynamic consistency. Moreover, this special solution to the problem is shown to be more general than previously explored in the literature. Instead of fitting to the lattice QCD data at the vanishing chemical potential, in this work, we adopt a “bottom-up” approach by assuming some analytic ansatzes that are manifestly thermodynamically consistent. The remaining physical quantities are subsequently derived, and possible implications are also addressed. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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30 pages, 1825 KiB

Open AccessArticle

Analysis of Identified Particle Transverse Momentum Spectra Produced in pp, p–Pb and Pb–Pb Collisions at the LHC Using TP-like Function

by Pei-Pin Yang, Mai-Ying Duan, Fu-Hu Liu and Raghunath Sahoo

Symmetry 2022, 14(8), 1530; https://doi.org/10.3390/sym14081530 - 26 Jul 2022

Cited by 6 | Viewed by 1422

Abstract

In the framework of a multi-source thermal model at the partonic level, we have analyzed transverse momentum spectra of hadrons measured by the ALICE Collaboration in proton–proton (

p p

or p–p) collisions at the center-of-mass energy of [...] Read more.

In the framework of a multi-source thermal model at the partonic level, we have analyzed transverse momentum spectra of hadrons measured by the ALICE Collaboration in proton–proton (

p p

or p–p) collisions at the center-of-mass energy of

\sqrt{s} = 7

and 13 TeV, proton–lead (p–Pb) collisions at

\sqrt{s_{N N}} = 5.02

TeV, and lead–lead (Pb–Pb) collisions at

\sqrt{s_{N N}} = 2.76

TeV. For mesons (baryons), the contributions of two (three) constituent quarks are considered, in which each quark contributes to hadron transverse momentum to obey the revised phenomenological Tsallis transverse momentum distribution for Maxwell–Boltzmann particles (the TP-like function, in short) with isotropic random azimuthal angles. Three main parameters, namely, the revised index

a_{0}

, effective temperature T, and entropy-related index n, are obtained, showing the same tendency for both small and large systems with respect to the centrality (or multiplicity) of events, the rest mass of hadrons, and the constituent mass of quarks. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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Review

Jump to: Research

27 pages, 627 KiB

Open AccessReview

Heavy-Flavour Jets in High-Energy Nuclear Collisions

by Sa Wang, Wei Dai, Enke Wang, Xin-Nian Wang and Ben-Wei Zhang

Symmetry 2023, 15(3), 727; https://doi.org/10.3390/sym15030727 - 15 Mar 2023

Cited by 5 | Viewed by 1701

Abstract

Reconstructed jets initiated from heavy quarks provide a powerful tool to probe the properties of the quark–gluon plasma (QGP) and to explore the mass hierarchy of jet quenching. In this article, we review the recent theoretical progresses on heavy-flavour jets in high-energy nuclear [...] Read more.

Reconstructed jets initiated from heavy quarks provide a powerful tool to probe the properties of the quark–gluon plasma (QGP) and to explore the mass hierarchy of jet quenching. In this article, we review the recent theoretical progresses on heavy-flavour jets in high-energy nuclear collisions at the RHIC and LHC. We focus on the yields and substructures of charm and bottom quark jets with jet-quenching effects, such as the nuclear modification factors, transverse momentum imbalance, angular correlation, radial profiles, fragmentation functions, the “dead-cone” effect, etc. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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14 pages, 782 KiB

Open AccessFeature PaperReview

Dilepton Program with Time-of-Flight Detector at the STAR Experiment

by Xin Dong, Lijuan Ruan, Ming Shao, Yongjie Sun, Zebo Tang, Zhangbu Xu, Wangmei Zha and Yifei Zhang

Symmetry 2023, 15(2), 392; https://doi.org/10.3390/sym15020392 - 02 Feb 2023

Viewed by 1251

Abstract

Pairs of lepton and antilepton (dilepton) in a continuous mass range are one of the most experimentally challenging and golden probes of the quark-gluon plasma (QGP) produced in heavy ion collisions because they do not strongly interact with the hot and dense medium, [...] Read more.

Pairs of lepton and antilepton (dilepton) in a continuous mass range are one of the most experimentally challenging and golden probes of the quark-gluon plasma (QGP) produced in heavy ion collisions because they do not strongly interact with the hot and dense medium, and reflect the properties of the medium at the time the dilepton is generated. The measurements of dileptons require lepton identification with high purity and high efficiency at large detector acceptance. STAR is one of two large experiments at the relativistic heavy ion collider with a primary goal of searching for the QGP and studying its properties. The STAR experiment launched a comprehensive dielectron (

e^{+} e^{-}

) program enabled by the time-of-flight (TOF) detector that had been fully installed in 2010. In this article, we review the decade-long

R & D

, the construction and performance of the STAR TOF detector, and dielectron measurements, including thermal dielectron production and dielectron production from the Breit–Wheeler process. Future perspectives are also discussed. Full article

(This article belongs to the Special Issue Heavy-Ion Collisions and Multiparticle Production)

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