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16 pages, 2302 KiB

Open AccessArticle

Toward the System Size Dependence of Anisotropic Flow in Heavy-Ion Collisions at

\sqrt{s_{N N}}

= 2–5 GeV

by Mikhail Mamaev and Arkadiy Taranenko

Particles 2023, 6(2), 622-637; https://doi.org/10.3390/particles6020036 - 2 Jun 2023

Cited by 5 | Viewed by 1849

Abstract

The study of the high-density equation of state (EOS) and the search for a possible phase transition in dense baryonic matter is the main goal of beam energy scan programs with relativistic heavy ions at energies

\sqrt{s_{N N}}

= 2–5 GeV. The [...] Read more.

The study of the high-density equation of state (EOS) and the search for a possible phase transition in dense baryonic matter is the main goal of beam energy scan programs with relativistic heavy ions at energies

\sqrt{s_{N N}}

= 2–5 GeV. The most stringent constraints currently available on the high-density EOS of symmetric nuclear matter come from the present measurements of directed (

v_{1}

) and elliptic flow (

v_{2}

) signals of protons in Au + Au collisions. In this energy range, the anisotropic flow is strongly affected by the presence of cold spectators due to the sizable passage time. The system size dependence of anisotropic flow may help to study the participant–spectator contribution and improve our knowledge of the EOS of symmetric nuclear matter. In this work, we discuss the layout of the upgraded BM@N experiment and the anticipated performance for differential anisotropic flow measurements of identified hadrons at Nuclotron energies:

\sqrt{s_{N N}}

= 2.3–3.5 GeV. Full article

(This article belongs to the Special Issue Selected Papers from "Physics Performance Studies at FAIR and NICA")

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12 pages, 1695 KiB

Open AccessArticle

Centrality Determination in Heavy-Ion Collisions Based on Monte-Carlo Sampling of Spectator Fragments

by Ilya Segal

Particles 2023, 6(2), 568-579; https://doi.org/10.3390/particles6020032 - 10 May 2023

Cited by 2 | Viewed by 2579

Abstract

The size and evolution of the matter created in a relativistic heavy-ion collision strongly depend on collision geometry, defined by centrality. Experimentally the centrality of collisions can be characterized by the measured multiplicities of the produced particles at midrapidity or by the energy [...] Read more.

The size and evolution of the matter created in a relativistic heavy-ion collision strongly depend on collision geometry, defined by centrality. Experimentally the centrality of collisions can be characterized by the measured multiplicities of the produced particles at midrapidity or by the energy measured in the forward rapidity region, which is sensitive to the spectator fragments. This serves as a proxy for the true collision centrality, as defined by the impact parameter in the models of collisions. In this work, the procedure for centrality determination based on Monte-Carlo sampling of spectator fragments has been proposed. The validity of the procedure has been checked using the fully reconstructed DCM-QGSM-SMM model events and published data from the NA61/SHINE experiment. Full article

(This article belongs to the Special Issue Selected Papers from "Physics Performance Studies at FAIR and NICA")

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10 pages, 393 KiB

Open AccessCommunication

Clustering in Oxygen Nuclei and Spectator Fragments in ¹⁶O–¹⁶O Collisions at the LHC

by Aleksandr Svetlichnyi, Savva Savenkov, Roman Nepeivoda and Igor Pshenichnov

Physics 2023, 5(2), 381-390; https://doi.org/10.3390/physics5020027 - 4 Apr 2023

Cited by 7 | Viewed by 2284

Abstract

A new version of the Abrasion–Ablation Monte Carlo for Colliders model with the Minimum Spanning Tree clusterization algorithm (AAMCC-MST) is used to simulate

^{16}

O–

^{16}

O collisions at the LHC, accounting for the presence of alpha-clustered states in

^{16}

O. The yields [...] Read more.

A new version of the Abrasion–Ablation Monte Carlo for Colliders model with the Minimum Spanning Tree clusterization algorithm (AAMCC-MST) is used to simulate

^{16}

O–

^{16}

O collisions at the LHC, accounting for the presence of alpha-clustered states in

^{16}

O. The yields of He, Li, Be, B, C and N spectator nuclei are calculated taking into account the pre-equilibrium clusterization of spectator matter and short-range correlations (SRC) between nucleons in

^{16}

O. The impact of

α

-clustering and SRC on the production of spectator neutrons and deuterons is investigated. The results on the production of spectator nucleons and fragments can help in evaluating the performance of Zero Degree Calorimeters in future studies of

^{16}

O–

^{16}

O collisions at the LHC. Full article

(This article belongs to the Special Issue From Heavy Ions to Astroparticle Physics)

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12 pages, 1294 KiB

Open AccessArticle

Pre-Equilibrium Clustering in Production of Spectator Fragments in Collisions of Relativistic Nuclei

by Roman Nepeivoda, Aleksandr Svetlichnyi, Nikita Kozyrev and Igor Pshenichnov

Particles 2022, 5(1), 40-51; https://doi.org/10.3390/particles5010004 - 29 Jan 2022

Cited by 7 | Viewed by 3199

Abstract

An algorithm of pre-equilibrium clustering of spectator matter based on the construction of the minimum spanning tree (MST) is presented. The algorithm was implemented in the Abrasion-Ablation Monte Carlo for Colliders (AAMCC) model designed to study the characteristics of spectator matter in collisions [...] Read more.

An algorithm of pre-equilibrium clustering of spectator matter based on the construction of the minimum spanning tree (MST) is presented. The algorithm was implemented in the Abrasion-Ablation Monte Carlo for Colliders (AAMCC) model designed to study the characteristics of spectator matter in collisions of relativistic nuclei. Due to accounting for the pre-equilibrium clusters in modelling

^{208}

Pb–

^{208}

Pb collisions at the LHC, the agreement of simulation results with experimental data on the average multiplicities of spectator nucleons was improved. The results of the AAMCC-MST were compared with experimental data on the interactions of

^{197}

Au nuclei in nuclear photoemulsion. Comparison of the yields of spectator nuclei calculated for

^{16}

O–

^{16}

O collisions with the yields measured in interactions of

^{16}

O with light nuclei of photoemulsion made it possible to estimate the effect of MST-clustering in small nuclear systems. Full article

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43 pages, 4748 KiB

Open AccessReview

Quintessential Inflation: A Tale of Emergent and Broken Symmetries

by Dario Bettoni and Javier Rubio

Galaxies 2022, 10(1), 22; https://doi.org/10.3390/galaxies10010022 - 27 Jan 2022

Cited by 33 | Viewed by 4329

Abstract

Quintessential inflation provides a unified description of inflation and dark energy in terms of a single scalar degree of freedom, the cosmon. We present here a comprehensive overview of this appealing paradigm, highlighting its key ingredients and keeping a reasonable and homogeneous level [...] Read more.

Quintessential inflation provides a unified description of inflation and dark energy in terms of a single scalar degree of freedom, the cosmon. We present here a comprehensive overview of this appealing paradigm, highlighting its key ingredients and keeping a reasonable and homogeneous level of details. After summarizing the cosmological evolution in a simple canonical case, we discuss how quintessential inflation can be embedded in a more general scalar-tensor formulation and its relation to variable gravity scenarios. Particular emphasis is placed on the role played by symmetries. In particular, we discuss the evolution of the cosmon field in terms of ultraviolet and infrared fixed points potentially appearing in quantum gravity formulations and leading to the emergence of scale invariance in the early and late Universe. The second part of the review is devoted to the exploration of the phenomenological consequences of the paradigm. First, we discuss how direct couplings of the cosmon field to matter may affect neutrinos masses and primordial structure formation. Second, we describe how Ricci-mediated couplings to spectator fields can trigger the spontaneous symmetry breaking of internal symmetries such as, but not limited to, global U(1) or Z

_{2}

symmetries, and affect a large variety of physical processes in the early Universe. Full article

(This article belongs to the Special Issue Latest Developments in the Quest for the Unification of Cosmic Inflation and Dark Energy)

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9 pages, 511 KiB

Open AccessArticle

Primordial Black Holes and a Common Origin of Baryons and Dark Matter

by Juan García-Bellido, Bernard Carr and Sébastien Clesse

Universe 2022, 8(1), 12; https://doi.org/10.3390/universe8010012 - 27 Dec 2021

Cited by 17 | Viewed by 3569

Abstract

The origin of the baryon asymmetry of the Universe (BAU) and the nature of dark matter are two of the most challenging problems in cosmology. We propose a scenario in which the gravitational collapse of large inhomogeneities at the quark-hadron epoch generates both [...] Read more.

The origin of the baryon asymmetry of the Universe (BAU) and the nature of dark matter are two of the most challenging problems in cosmology. We propose a scenario in which the gravitational collapse of large inhomogeneities at the quark-hadron epoch generates both the baryon asymmetry and most of the dark matter in the form of primordial black holes (PBHs). This is due to the sudden drop in radiation pressure during the transition from a quark-gluon plasma to non-relativistic hadrons. The collapse to a PBH is induced by fluctuations of a light spectator scalar field in rare regions and is accompanied by the violent expulsion of surrounding material, which might be regarded as a sort of “primordial supernova". The acceleration of protons to relativistic speeds provides the ingredients for efficient baryogenesis around the collapsing regions and its subsequent propagation to the rest of the Universe. This scenario naturally explains why the observed BAU is of order the PBH collapse fraction and why the baryons and dark matter have comparable densities. The predicted PBH mass distribution ranges from subsolar to several hundred solar masses. This is compatible with current observational constraints and could explain the rate, mass and low spin of the black hole mergers detected by LIGO-Virgo. Future observations will soon be able to test this scenario. Full article

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18 pages, 772 KiB

Open AccessReview

Description of (Hyper-)Fragments in Hadron-Induced Reactions

by Theodoros Gaitanos

Symmetry 2021, 13(10), 1887; https://doi.org/10.3390/sym13101887 - 7 Oct 2021

Cited by 1 | Viewed by 1574

Abstract

In this article we review the important role of non-equilibrium dynamics in reactions induced by ions and hadron beams to understand the fragmentation processes inside hadronic media. We discuss the single-particle dynamics in specific sources such as spectators in heavy-ion collisions and residual [...] Read more.

In this article we review the important role of non-equilibrium dynamics in reactions induced by ions and hadron beams to understand the fragmentation processes inside hadronic media. We discuss the single-particle dynamics in specific sources such as spectators in heavy-ion collisions and residual nuclear targets in hadron-induced reactions. Particular attention is given to the dynamics of hyperons. We further discuss the question regarding the onset of local instabilities, which are relevant for the appearance of fragmentation phenomena in nuclear reactions. We apply the theoretical formalism, that is, semi-classical transport embedded with statistical methods of nuclear fragmentation, to reactions induced by light ions and hadron beams. We discuss the results of nuclear fragmentation and, in particular, examine the formation of hypernuclei. Such studies are important for obtaining a deeper understanding of the equation of state in fragmenting matter and are relevant for forthcoming experiments, such as PANDA at FAIR and J-PARC in Japan. Full article

(This article belongs to the Special Issue Equation of State of Nuclear Matter with Correlations and Cluster Formation)

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7 pages, 1370 KiB

Open AccessArticle

Data-Driven Methods for Spectator Symmetry Plane Estimation in CBM Experiment at FAIR

by Oleg Golosov, Ilya Selyuzhenkov and Evgeny Kashirin

Particles 2021, 4(3), 354-360; https://doi.org/10.3390/particles4030030 - 21 Jul 2021

Cited by 2 | Viewed by 3031

Abstract

The Compressed Baryonic Matter experiment (CBM) at FAIR aims to study the area of the QCD phase diagram at high net baryon densities and moderate temperatures with collisions of heavy ions at

\sqrt{s_{NN}} = 2.8

–4.9 GeV. The anisotropic transverse flow is [...] Read more.

The Compressed Baryonic Matter experiment (CBM) at FAIR aims to study the area of the QCD phase diagram at high net baryon densities and moderate temperatures with collisions of heavy ions at

\sqrt{s_{NN}} = 2.8

–4.9 GeV. The anisotropic transverse flow is one of the most important observable phenomena in a study of the properties of matter created in such collisions. Flow measurements require the knowledge of the collision symmetry plane, which can be determined from the deflection of the collision spectators in the plane transverse to the direction of the moving ions. The CBM performance for projectile spectator symmetry plane estimation is studied with GEANT4 Monte Carlo simulations using collisions of gold ions with beam momentum of

12 A

GeV/c generated with the DCM-QGSM-SMM model. Different data-driven methods to extract the correction factor in flow analysis for the resolution of the spectator symmetry plane estimated with the CBM Projectile Spectator Detector are investigated. Full article

(This article belongs to the Special Issue Analysis Techniques and Physics Performance Studies for FAIR and NICA)

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9 pages, 310 KiB

Open AccessArticle

Using Spectator Matter for Centrality Determination in Nucleus-Nucleus Collisions

by Aleksandr Svetlichnyi, Roman Nepeyvoda and Igor Pshenichnov

Particles 2021, 4(2), 227-235; https://doi.org/10.3390/particles4020021 - 23 May 2021

Cited by 3 | Viewed by 3325

Abstract

One of the common methods to measure the centrality of nucleus-nucleus collision events consists of detecting forward spectator neutrons. Because of non-monotonic dependence of neutron numbers on centrality, other characteristics of spectator matter in

^{197}

Au–

^{197}

Au collisions at NICA must be [...] Read more.

One of the common methods to measure the centrality of nucleus-nucleus collision events consists of detecting forward spectator neutrons. Because of non-monotonic dependence of neutron numbers on centrality, other characteristics of spectator matter in

^{197}

Au–

^{197}

Au collisions at NICA must be considered to improve the centrality determination. The numbers of spectator deuterons and

α

-particles and the forward–backward asymmetry of the numbers of free spectator nucleons were calculated with the Abrasion–Ablation Monte Carlo for Colliders (AAMCC) model as functions of event centrality. It was shown that the number of charged fragments per spectator nucleon decreases monotonically with an increase of the impact parameter, and thus can be used to estimate the collision centrality. The conditional probabilities that a given event with specific spectator characteristics belongs to a certain centrality class were calculated by means of AAMCC. Such probabilities can be used as an input to Bayesian or other machine-learning approaches to centrality determination in

^{197}

Au–

^{197}

Au collisions. Full article

(This article belongs to the Special Issue Analysis Techniques and Physics Performance Studies for FAIR and NICA)

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8 pages, 3010 KiB

Open AccessArticle

Influence of Backside Energy Leakages from Hadronic Calorimeters on Fluctuation Measures in Relativistic Heavy-Ion Collisions

by Andrey Seryakov

Universe 2019, 5(5), 126; https://doi.org/10.3390/universe5050126 - 23 May 2019

Cited by 1 | Viewed by 2449

Abstract

The phase diagram of the strongly interacting matter is the main research subject for different current and future experiments in high-energy physics. System size and energy scan programs aim to find a possible critical point. One of such programs was accomplished by the [...] Read more.

The phase diagram of the strongly interacting matter is the main research subject for different current and future experiments in high-energy physics. System size and energy scan programs aim to find a possible critical point. One of such programs was accomplished by the fixed-target NA61/SHINE experiment in 2018. It includes six beam energies and six colliding systems: p + p, Be + Be, Ar + Sc, Xe + La, Pb + Pb and p + Pb. In this study, we discuss how the efficiency of centrality selection by forward spectators influences multiplicity and fluctuation measures and how this influence depends on the size of colliding systems. We use SHIELD and EPOS Monte-Carlo (MC) generators along with the wounded nucleon model, introduce a probability to lose a forward spectator and spectator energy loss. We show that for light colliding systems such as Be or Li even a small inefficiency in centrality selection has a dramatic impact on multiplicity scaled variance. Conversely, heavy systems such as Ar + Sc are much less prone to the effect. Full article

(This article belongs to the Special Issue The Zimányi School and Analytic Hydrodynamics in High Energy Physics)

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10 pages, 201 KiB

Open AccessArticle

Proposal for Sustainable Dynamic Lighting in Sport Facilities to Decrease Violence among Spectators

by Raquel Amorim, Valentín Molina-Moreno and Antonio Peña-García

Sustainability 2016, 8(12), 1298; https://doi.org/10.3390/su8121298 - 10 Dec 2016

Cited by 16 | Viewed by 5600

Abstract

Violence among spectators at sports events has become a serious problem, not only for its evident impact on safety, but also from the perspective of environmental, cultural, economic and social sustainability. Although it could be considered a purely social problem, some solutions could [...] Read more.

Violence among spectators at sports events has become a serious problem, not only for its evident impact on safety, but also from the perspective of environmental, cultural, economic and social sustainability. Although it could be considered a purely social problem, some solutions could come from a smart and efficient design and management of the lighting installations. Thus, the management of sports installations requires deep considerations of lighting technology for three reasons: (1) accurate illumination allows the users to achieve their visual task with comfort and safety; (2) the energy consumption of sports facilities can be decreased with an efficient design of the lighting installation; and (3) the lighting impacts some psychological and physiological aspects such as arousal, stress or relaxation which are directly related to violence. In this work, the recent advances on the matter of light sources and non-visual effects of light are deployed within a new proposal of dynamic Light-emitting diode (LED) lighting to decrease violence among spectators. Here, sustainable sports facilities are considered from a global perspective where accurate illumination in each zone (court, bleachers, training rooms and surrounding streets) plays an important role in violence avoidance. Full article

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