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High Energy Physics
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High Energy Physics

A topical collection in Particles (ISSN 2571-712X).

Viewed by 26781

Editor

Prof. Dr. Alexandru Jipa

E-Mail Website
Guest Editor
Faculty of Physics, University of Bucharest, Bucharest, Romania
Interests: relativistic and ultrarelativistic heavy ion physics; nuclear and particle physics; astroparticle physics; applied nuclear physics
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

In 1948, Dr. Phyllis Freier and his team discovered the relativistic heavy ions component of primary cosmic rays. a new field in nuclear and particle physics was created. Twenty-two years later, in August 1970, the first heavy ions beam was used at the JINR Dubna to evidence the cumulative negative ion production in DC collisions at 5 A GeV, using the Synchrophasotron U-10.

In the fifty years of relativistic and ultra-relativistic heavy ion physics using accelerator systems, many important results and discoveries have been reported, including those related to quark–gluon plasma formation and with the Big Bang cosmological scenario.

Therefore, the goal of the Editorial Board of the Particles journal is to dedicate a collection from this very interesting and dynamic field to present significant experimental results; new experiments and their goals; new theoretical ways for investigating the behavior of the very hot and dense nuclear matter formed in such collisions, in agreement with the collision geometry and collision energy; support for old and new comparisons of the predictions of the simulation codes and experimental results; and the insertion of new methods and ideas for these codes.   

The major experiments performed at Relativistic Heavy Ion Collider (RHIC) from BNL, USA, as well as at the Large Hadron Collider (LHC) at CERN Geneva, have revealed the formation of quark–gluon plasma and a significant hydrodynamic collective behavior, similar to a nearly perfect fluid. Some clarifications regarding the evolution of the Universe have been obtained. In agreement with cosmological scenarios, including Gamow's “Big Bang" scenario, quark–gluon plasma appears a few microseconds after, and, therefore, it is possible to reproduce the conditions existing at that time in Universe in the laboratory.

There are other interesting nuclear matter phases, and the types of possible phase transitions are especially important for the study of the structure of nuclear matter and for the possible interactions. The current phase diagram of the nuclear matter still has areas that are not fully covered by the experimental data and results. Therefore, some laboratories have made ​​efforts to achieve a scan over a wide range of energies, using the same experimental arrangement, with normalization in proton–proton collisions. There are remarkable results from RHIC-BNL, and from the efforts at SPS-CERN and the Tevatron (USA). There are also experimental results at lower energies from JINR Dubna, LNBL, etc.

On the other hand, the scientific community has proposed building new different acceleration and detector systems to cover other energies, especially in the phase transition region. Two projects are of great interest, namely FAIR (the Facility for Antiproton and Ion Research) at GSI Darmstadt (Germany) (www.gsi.de) and NICA (the Nuclotron-based Ion Collider Facility) at JINR Dubna (Russia). Both projects are now in an advanced stage, and the proposed experiments are already reaching the completion of the technical design reports for the detectors.

Therefore, the goal of the Editorial Board of Particles is stimulating and demanding, and authors should offer insights on these interesting aspects both experimentally and theoretically.

Prof. Dr. Alexandru Jipa
Guest Editor

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Keywords

  • experiments
  • collision geometry and bulk properties
  • collision dynamics
  • hydrodynamics
  • thermalization
  • flow
  • correlations
  • fluctuations
  • phase transitions
  • experimental signals

Published Papers (12 papers)

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2024

Jump to: 2023, 2022, 2021, 2020

6 pages, 193 KiB  
Article
A Note on Blind Techniques for New Physics Searches in Particle Physics
by Sergei V. Chekanov
Particles 2024, 7(3), 647-652; https://doi.org/10.3390/particles7030037 - 24 Jul 2024
Viewed by 577
Abstract
This paper attempts to classify various blinding strategies used in particle physics. It argues that the blinding technique is not used consistently throughout searches for new physics. More importantly, the blinding technique, in its traditional sense, cannot be applicable for many current and [...] Read more.
This paper attempts to classify various blinding strategies used in particle physics. It argues that the blinding technique is not used consistently throughout searches for new physics. More importantly, the blinding technique, in its traditional sense, cannot be applicable for many current and future searches when the statistical precision of data significantly exceeds the current level of our understanding of Standard Model (SM) backgrounds. Full article
26 pages, 1663 KiB  
Article
New Aspect of Chiral SU(2) and U(1) Axial Breaking in QCD
by Chuan-Xin Cui, Jin-Yang Li, Shinya Matsuzaki, Mamiya Kawaguchi and Akio Tomiya
Particles 2024, 7(1), 237-263; https://doi.org/10.3390/particles7010014 - 9 Mar 2024
Cited by 6 | Viewed by 1315
Abstract
The violation of the U(1) axial symmetry in QCD is stricter than the chiral SU(2) breaking simply because of the presence of the quantum axial anomaly. If the QCD gauge coupling is sent to zero (the [...] Read more.
The violation of the U(1) axial symmetry in QCD is stricter than the chiral SU(2) breaking simply because of the presence of the quantum axial anomaly. If the QCD gauge coupling is sent to zero (the asymptotic free limit, where the U(1) axial anomaly does not exist), the strength of the U(1) axial breaking coincides with that of the chiral SU(2) breaking, which we, in short, call an axial–chiral coincidence. This coincidence is trivial since QCD then becomes a non-interacting theory. Actually, there exists another limit in the QCD parameter space, where an axial–chiral coincidence occurs even with nonzero QCD gauge coupling, which can be dubbed a nontrivial coincidence: it is the case with the massive light quarks (ml≠0) and the massless strange quark (ms=0) due to the flavor-singlet nature of the topological susceptibility. This coincidence is robust and tied to the anomalous chiral Ward–Takahashi identity, which is operative even at hot QCD. This implies that the chiral SU(2) symmetry is restored simultaneously with the U(1) axial symmetry at high temperatures. This simultaneous restoration is independent of ml(≠0) and, hence, is irrespective of the order of the chiral phase transition. In this paper, we discuss how the real-life QCD can be evolved from the nontrivial chiral–axial coincidence limit by working on a Nambu–Jona–Lasinio model with the U(1) axial anomaly contribution properly incorporated. It is shown that, at high temperatures, the large differences between the restorations of the chiral SU(2) symmetry and the U(1) axial symmetry for two light quarks and a sufficiently large current mass for the strange quark are induced by a significant interference of the topological susceptibility. Thus, the deviation from the nontrivial coincidence, which is monitored by the strange quark mass controlling the topological susceptibility, provides a new way of understanding the chiral SU(2) and U(1) axial breaking in QCD. Full article
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2023

Jump to: 2024, 2022, 2021, 2020

16 pages, 323 KiB  
Review
R-Symmetries and Curvature Constraints in A-Twisted Heterotic Landau–Ginzburg Models
by Richard S. Garavuso
Particles 2023, 6(3), 746-761; https://doi.org/10.3390/particles6030047 - 7 Aug 2023
Viewed by 1048
Abstract
In this paper, we discuss various aspects of a class of A-twisted heterotic Landau–Ginzburg models on a Kähler variety X. We provide a classification of the R-symmetries in these models which allow the A-twist to be implemented, focusing on the case in [...] Read more.
In this paper, we discuss various aspects of a class of A-twisted heterotic Landau–Ginzburg models on a Kähler variety X. We provide a classification of the R-symmetries in these models which allow the A-twist to be implemented, focusing on the case in which the gauge bundle is either a deformation of the tangent bundle of X or a deformation of a sub-bundle of the tangent bundle of X. Some anomaly-free examples are provided. The curvature constraint imposed by supersymmetry in these models when the superpotential is not holomorphic is reviewed. Constraints of this nature have been used to establish properties of analogues of pullbacks of Mathai–Quillen forms which arise in the correlation functions of the corresponding A-twisted or B-twisted heterotic Landau–Ginzburg models. The analogue most relevant to this paper is a deformation of the pullback of a Mathai–Quillen form. We discuss how this deformation may arise in the class of models studied in this paper. We then comment on how analogues of pullbacks of Mathai–Quillen forms not discussed in previous work may be obtained. Standard Mathai–Quillen formalism is reviewed in an appendix. We also include an appendix which discusses the deformation of the pullback of a Mathai–Quillen form. Full article
6 pages, 232 KiB  
Brief Report
The Invariance of Inelastic Overlap Function
by Sergey Mikhailovich Troshin and Nikolai Evgenjevich Tyurin
Particles 2023, 6(1), 239-244; https://doi.org/10.3390/particles6010013 - 3 Feb 2023
Cited by 1 | Viewed by 1230
Abstract
In this study, we consider the symmetry property of the inelastic overlap function and its relation to the reflective scattering mode appearance. This symmetry property disfavors an exclusion of one of the scattering modes—the reflective mode—when approaching the asymptotic limit. Predominance of the [...] Read more.
In this study, we consider the symmetry property of the inelastic overlap function and its relation to the reflective scattering mode appearance. This symmetry property disfavors an exclusion of one of the scattering modes—the reflective mode—when approaching the asymptotic limit. Predominance of the particular mode correlates with the energy and impact parameters ranges. Full article

2022

Jump to: 2024, 2023, 2021, 2020

9 pages, 387 KiB  
Article
Dynamical Pair Production at Sub-Barrier Energies for Light Nuclei
by Thomas Settlemyre, Hua Zheng and Aldo Bonasera
Particles 2022, 5(4), 580-588; https://doi.org/10.3390/particles5040041 - 17 Dec 2022
Cited by 2 | Viewed by 1489
Abstract
In the collision of two heavy ions, the strong repulsion coming from the Coulomb field is enough to produce e+e− pair(s) from vacuum fluctuations. The energy is provided by the kinetic energy of the ions and the Coulomb interaction at [...] Read more.
In the collision of two heavy ions, the strong repulsion coming from the Coulomb field is enough to produce e+e− pair(s) from vacuum fluctuations. The energy is provided by the kinetic energy of the ions and the Coulomb interaction at the production point. If, for instance, the electron is located at the center of mass (C.M.) of the two ions moving along the z-axis, and the positron is at a distance x from the electron, the ions can be accelerated towards each other since the Coulomb barrier is lowered by the presence of the electron. This screening results in an increase in the kinetic energy of the colliding ions and may result in an increase in the fusion probability of light ions above the adiabatic limit. Full article
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14 pages, 1768 KiB  
Article
Unruh Effect and Information Entropy Approach
by Maksym Teslyk, Larissa Bravina and Evgeny Zabrodin
Particles 2022, 5(2), 157-170; https://doi.org/10.3390/particles5020014 - 27 May 2022
Cited by 5 | Viewed by 3199 | Correction
Abstract
The Unruh effect can be considered a source of particle production. The idea has been widely employed in order to explain multiparticle production in hadronic and heavy-ion collisions at ultrarelativistic energies. The attractive feature of the application of the Unruh effect as a [...] Read more.
The Unruh effect can be considered a source of particle production. The idea has been widely employed in order to explain multiparticle production in hadronic and heavy-ion collisions at ultrarelativistic energies. The attractive feature of the application of the Unruh effect as a possible mechanism of the multiparticle production is the thermalized spectra of newly produced particles. In the present paper, the total entropy generated by the Unruh effect is calculated within the framework of information theory. In contrast to previous studies, here the calculations are conducted for the finite time of existence of the non-inertial reference frame. In this case, only a finite number of particles are produced. The dependence on the mass of the emitted particles is taken into account. Analytic expression for the entropy of radiated boson and fermion spectra is derived. We study also its asymptotics corresponding to low- and high-acceleration limiting cases. The obtained results can be further generalized to other intrinsic degrees of freedom of the emitted particles, such as spin and electric charge. Full article
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11 pages, 1925 KiB  
Article
The Novel Scaling of Tsallis Parameters from the Transverse Momentum Spectra of Charged Particles in Heavy-Ion Collisions
by Junqi Tao, Weihao Wu, Meng Wang, Hua Zheng, Wenchao Zhang, Lilin Zhu and Aldo Bonasera
Particles 2022, 5(2), 146-156; https://doi.org/10.3390/particles5020013 - 9 May 2022
Cited by 7 | Viewed by 2584
Abstract
The transverse momentum (pT) spectra of charged particles measured in Au + Au collisions from the beam energy scan (BES) program, Cu + Cu collisions at sNN=62.4, 200 GeV at the RHIC and Pb + [...] Read more.
The transverse momentum (pT) spectra of charged particles measured in Au + Au collisions from the beam energy scan (BES) program, Cu + Cu collisions at sNN=62.4, 200 GeV at the RHIC and Pb + Pb, Xe + Xe collisions at the LHC are investigated in the framework of Tsallis thermodynamics. The theory can describe the experimental data well for all the collision systems, energies and centralities investigated. The collision energy and centrality dependence of the Tsallis distribution parameters, i.e., the temperature T and the nonextensive parameter q, for the A + A collisions are also studied and discussed. A novel scaling between the temperature divided by the natural logarithm of collision energy (T/lns) and the nonextensive parameter q is presented. Full article
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19 pages, 6065 KiB  
Article
Pioneering the Equation of State of Dense Nuclear Matter with Strange Particles Emitted in Heavy-Ion Collisions: The KaoS Experiment at GSI
by Peter Senger
Particles 2022, 5(1), 21-39; https://doi.org/10.3390/particles5010003 - 17 Jan 2022
Cited by 4 | Viewed by 2869
Abstract
High-energy heavy-ion collisions offer the unique possibility to study fundamental properties of nuclear matter in the laboratory, which are relevant for our understanding of the structure of compact stellar objects and the dynamics of neutron star mergers. Of particular interest are the nuclear [...] Read more.
High-energy heavy-ion collisions offer the unique possibility to study fundamental properties of nuclear matter in the laboratory, which are relevant for our understanding of the structure of compact stellar objects and the dynamics of neutron star mergers. Of particular interest are the nuclear matter equation of state (EOS), the in-medium modifications of hadrons and the degrees of freedom of matter at high densities and temperatures. Pioneering experiments exploring the EOS for symmetric matter were performed at the SIS18 accelerator of GSI, measuring, as function of beam energy, the collective flow of protons and of light fragments and subthreshold strangeness production. These data were reproduced by various microscopic transport model calculations, providing, up to date, the best constraint for the EOS of symmetric matter with an incompressibility of about 200 MeV for densities up to twice the saturation density. This article reviews the experimental results on subthreshold kaon production together with the theoretical interpretation and gives a brief outlook towards future experiments at higher densities. Full article
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2021

Jump to: 2024, 2023, 2022, 2020

9 pages, 331 KiB  
Communication
Azimuthal Correlations of D Mesons with Charged Particles in Simulations with the ALICE Experiment
by Eszter Frajna and Robert Vertesi
Particles 2021, 4(4), 512-520; https://doi.org/10.3390/particles4040037 - 1 Nov 2021
Viewed by 2627
Abstract
In this work, we present the results of a component-level analysis with Monte Carlo simulations, which aid the interpretation of recent ALICE results of the azimutal correlation distribution of prompt D mesons with charged hadrons in pp and p–Pb collisions at sNN [...] Read more.
In this work, we present the results of a component-level analysis with Monte Carlo simulations, which aid the interpretation of recent ALICE results of the azimutal correlation distribution of prompt D mesons with charged hadrons in pp and p–Pb collisions at sNN = 5.02 TeV. Parton-level contributions and fragmentation properties are evaluated. Charm and beauty contributions are compared in order to identify the observables that serve as sensitive probes of the production and hadronisation of heavy quarks. Full article
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6 pages, 260 KiB  
Conference Report
Direct-Channel Option of the Forward Slope Increase
by Sergey Troshin and Nikolai Tyurin
Particles 2021, 4(3), 391-396; https://doi.org/10.3390/particles4030033 - 9 Sep 2021
Cited by 3 | Viewed by 2515
Abstract
The LHC data on the elastic scattering indicate that the forward slope increase is not consistent with the contributions of the simple Regge poles only with the linear Regge trajectories. The dynamics might be associated with unitarization in the direct channel of reaction. [...] Read more.
The LHC data on the elastic scattering indicate that the forward slope increase is not consistent with the contributions of the simple Regge poles only with the linear Regge trajectories. The dynamics might be associated with unitarization in the direct channel of reaction. We discuss the problems of the Regge model and provide a respective illustration of the direct-channel option. Full article
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10 pages, 468 KiB  
Article
On the Shape of Nucleons at High Energies
by Maksim L. Nekrasov
Particles 2021, 4(3), 381-390; https://doi.org/10.3390/particles4030032 - 21 Aug 2021
Cited by 3 | Viewed by 2692
Abstract
A scenario of the evolution of the shape of nucleons with increasing energy is described in the framework of an extended parton model, which consistently takes into account the transverse motion of the partons. At the energy E up to LHC, the nucleons [...] Read more.
A scenario of the evolution of the shape of nucleons with increasing energy is described in the framework of an extended parton model, which consistently takes into account the transverse motion of the partons. At the energy E up to LHC, the nucleons have the form of a spheroid which expands as lnE in the transverse directions and grows linearly in E in the longitudinal direction. With a further increase in the energy, a mode of correlated behavior of the partons is established, which stops the longitudinal growth. Simultaneously, the expansion in the transverse directions changes to lnE, and a hollow mostly free of partons is formed inside the nucleons along the central axis in the direction of their motion. Numerical estimates of the corresponding parameters are obtained. Full article
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2020

Jump to: 2024, 2023, 2022, 2021

17 pages, 337 KiB  
Article
Direct Photons from Hot Quark Matter in Renormalized Finite-Time-Path QED
by Ivan Dadić, Dubravko Klabučar and Domagoj Kuić
Particles 2020, 3(4), 676-692; https://doi.org/10.3390/particles3040044 - 20 Oct 2020
Cited by 3 | Viewed by 2565
Abstract
Within the finite-time-path out-of-equilibrium quantum field theory (QFT), we calculate direct photon emission from early stages of heavy ion collisions, from a narrow window, in which uncertainty relations are still important and they provide a new mechanism for production of photons. The basic [...] Read more.
Within the finite-time-path out-of-equilibrium quantum field theory (QFT), we calculate direct photon emission from early stages of heavy ion collisions, from a narrow window, in which uncertainty relations are still important and they provide a new mechanism for production of photons. The basic difference with respect to earlier calculations, leading to diverging results, is that we use renormalized QED of quarks and photons. Our result is a finite contribution that is consistent with uncertainty relations. Full article
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