Particles

64 pages, 5437 KiB

Open AccessEditor’s ChoiceReview

by Minghui Ding, Craig D. Roberts and Sebastian M. Schmidt

Particles 2023, 6(1), 57-120; https://doi.org/10.3390/particles6010004 - 11 Jan 2023

Cited by 50 | Viewed by 23637

Visible matter is characterised by a single mass scale; namely, the proton mass. The proton’s existence and structure are supposed to be described by quantum chromodynamics (QCD); yet, absent Higgs boson couplings, chromodynamics is scale-invariant. Thus, if the Standard Model is truly a [...] Read more.

Visible matter is characterised by a single mass scale; namely, the proton mass. The proton’s existence and structure are supposed to be described by quantum chromodynamics (QCD); yet, absent Higgs boson couplings, chromodynamics is scale-invariant. Thus, if the Standard Model is truly a part of the theory of Nature, then the proton mass is an emergent feature of QCD; and emergent hadron mass (EHM) must provide the basic link between theory and observation. Nonperturbative tools are necessary if such connections are to be made; and in this context, we sketch recent progress in the application of continuum Schwinger function methods to an array of related problems in hadron and particle physics. Special emphasis is given to the three pillars of EHM—namely, the running gluon mass, process-independent effective charge, and running quark mass; their role in stabilising QCD; and their measurable expressions in a diverse array of observables. Full article

(This article belongs to the Special Issue Strong Interactions in the Standard Model: Massless Bosons to Compact Stars)

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27 pages, 1516 KiB

Open AccessEditor’s ChoiceArticle

Constraints on Nuclear Symmetry Energy Parameters

by James M. Lattimer

Particles 2023, 6(1), 30-56; https://doi.org/10.3390/particles6010003 - 4 Jan 2023

Cited by 66 | Viewed by 3634

Abstract

A review is made of constraints on the nuclear symmetry energy parameters arising from nuclear binding energy measurements, theoretical chiral effective field predictions of neutron matter properties, the unitary gas conjecture, and measurements of neutron skin thicknesses and dipole polarizabilities. While most studies [...] Read more.

A review is made of constraints on the nuclear symmetry energy parameters arising from nuclear binding energy measurements, theoretical chiral effective field predictions of neutron matter properties, the unitary gas conjecture, and measurements of neutron skin thicknesses and dipole polarizabilities. While most studies have been confined to the parameters

S_{V}

and L, the important roles played by, and constraints on

K_{sym}

, or, equivalently, the neutron matter incompressibility

K_{N}

, are discussed. Strong correlations among

S_{V}, L

, and

K_{N}

are found from both nuclear binding energies and neutron matter theory. However, these correlations somewhat differ in the two cases, and those from neutron matter theory have smaller uncertainties. To 68% confidence, it is found from neutron matter theory that

S_{V} = 32.0 \pm 1.1

MeV,

L = 51.9 \pm 7.9

MeV and

K_{N} = 152.2 \pm 38.1

MeV. Theoretical predictions for neutron skin thickness and dipole polarizability measurements of the neutron-rich nuclei

^{48}

Ca,

^{120}

Sn, and

^{208}

Pb are compared to recent experimental measurements, most notably the CREX and PREX neutron skin experiments from Jefferson Laboratory. By themselves, PREX I+II measurements of

^{208}

Pb and CREX measurement of

^{48}

Ca suggest

L = 121 \pm 47

MeV and

L = - 5 \pm 40

MeV, respectively, to 68% confidence. However, we show that nuclear interactions optimally satisfying both measurements imply

L = 53 \pm 13

MeV, nearly the range suggested by either nuclear mass measurements or neutron matter theory, and is also consistent with nuclear dipole polarizability measurements. This small parameter range implies

R_{1.4} = 11.6 \pm 1.0

km and

Λ_{1.4} = 228_{- 90}^{+ 148}

, which are consistent with NICER X-ray and LIGO/Virgo gravitational wave observations of neutron stars. Full article

(This article belongs to the Special Issue Selected Papers from “The Modern Physics of Compact Stars and Relativistic Gravity 2021”)

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15 pages, 456 KiB

Open AccessEditor’s ChoiceArticle

Beta Decay in Medium-Mass Nuclei with the In-Medium Similarity Renormalization Group

by Steven Ragnar Stroberg

Particles 2021, 4(4), 521-535; https://doi.org/10.3390/particles4040038 - 18 Nov 2021

Cited by 8 | Viewed by 3482

Abstract

We review the status of ab initio calculations of allowed beta decays (both Fermi and Gamow–Teller), within the framework of the valence-space in-medium similarity renormalization group approach. Full article

(This article belongs to the Special Issue Beta-Decay Processes in Nuclear Systems)

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21 pages, 555 KiB

Open AccessEditor’s ChoiceArticle

Quantization of Gravity and Finite Temperature Effects

by I. Y. Park

Particles 2021, 4(4), 468-488; https://doi.org/10.3390/particles4040035 - 14 Oct 2021

Cited by 4 | Viewed by 2966

Abstract

Gravity is perturbatively renormalizable for the physical states which can be conveniently defined via foliation-based quantization. In recent sequels, one-loop analysis was explicitly carried out for Einstein-scalar and Einstein-Maxwell systems. Various germane issues and all-loop renormalizability have been addressed. In the present work [...] Read more.

Gravity is perturbatively renormalizable for the physical states which can be conveniently defined via foliation-based quantization. In recent sequels, one-loop analysis was explicitly carried out for Einstein-scalar and Einstein-Maxwell systems. Various germane issues and all-loop renormalizability have been addressed. In the present work we make further progress by carrying out several additional tasks. Firstly, we present an alternative 4D-covariant derivation of the physical state condition by examining gauge choice-independence of a scattering amplitude. To this end, a careful dichotomy between the ordinary, and large gauge symmetries is required and appropriate gauge-fixing of the ordinary symmetry must be performed. Secondly, vacuum energy is analyzed in a finite-temperature setup. A variant optimal perturbation theory is implemented to two-loop. The renormalized mass determined by the optimal perturbation theory turns out to be on the order of the temperature, allowing one to avoid the cosmological constant problem. The third task that we take up is examination of the possibility of asymptotic freedom in finite-temperature quantum electrodynamics. In spite of the debates in the literature, the idea remains reasonable. Full article

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71 pages, 2928 KiB

Open AccessEditor’s ChoiceReview

Radiative Corrections to Semileptonic Beta Decays: Progress and Challenges

by Chien-Yeah Seng

Particles 2021, 4(4), 397-467; https://doi.org/10.3390/particles4040034 - 28 Sep 2021

Cited by 18 | Viewed by 3994

Abstract

We review some recent progress in the theory of electroweak radiative corrections in semileptonic decay processes. The resurrection of the so-called Sirlin’s representation based on current algebra relations permits a clear separation between the perturbatively-calculable and incalculable pieces in the [...] Read more.

We review some recent progress in the theory of electroweak radiative corrections in semileptonic decay processes. The resurrection of the so-called Sirlin’s representation based on current algebra relations permits a clear separation between the perturbatively-calculable and incalculable pieces in the

O (G_{F} ?)

radiative corrections. The latter are expressed as compact hadronic matrix elements that allow systematic non-perturbative analysis such as dispersion relation and lattice QCD. This brings substantial improvements to the precision of the electroweak radiative corrections in semileptonic decays of pion, kaon, free neutron and

J^{P} = 0^{+}

nuclei that are important theory inputs in precision tests of the Standard Model. Unresolved issues and future prospects are discussed. Full article

(This article belongs to the Special Issue Beta-Decay Processes in Nuclear Systems)

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20 pages, 1405 KiB

Open AccessEditor’s ChoiceArticle

Some Examples of Calculation of Massless and Massive Feynman Integrals

by Anatoly V. Kotikov

Particles 2021, 4(3), 361-380; https://doi.org/10.3390/particles4030031 - 14 Aug 2021

Cited by 2 | Viewed by 3275

Abstract

We show some examples of calculations of massless and massive Feynman integrals. Full article

13 pages, 3194 KiB

Open AccessEditor’s ChoiceArticle

Heavy-Ion Collisions at FAIR-NICA Energies

by Peter Senger

Particles 2021, 4(2), 214-226; https://doi.org/10.3390/particles4020020 - 17 May 2021

Cited by 11 | Viewed by 4926

Abstract

The “Facility for Antiproton and Ion Research” (FAIR) in Darmstadt, Germany, and the “Nuclotron-based Ion Collider Facility” (NICA) in Dubna, Russia, are two accelerator centers under construction. FAIR will provide beams and experimental setups to perform forefront research in hadron, nuclear, atomic, and [...] Read more.

The “Facility for Antiproton and Ion Research” (FAIR) in Darmstadt, Germany, and the “Nuclotron-based Ion Collider Facility” (NICA) in Dubna, Russia, are two accelerator centers under construction. FAIR will provide beams and experimental setups to perform forefront research in hadron, nuclear, atomic, and plasma physics, as well as in radiation biology and material science. At NICA, a unique research program on nuclear matter and spin physics will be conducted. Both facilities will execute experiments to explore the properties of QCD matter at neutron star core densities, in order to study the high-density equation of state, and to shed light on the quark degrees-of-freedom emerging in QCD matter at high densities. The research programs will be performed at FAIR with the CBM experiment, and at NICA with the MPD setup at the collider, and with the BM@N experiment at the Nuclotron. These three experiments are complementary, with respect to the beam energy. The physics programs and the relevant experimental observables will be discussed. Full article

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

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11 pages, 356 KiB

Open AccessEditor’s ChoiceArticle

Extracting Hypernuclear Properties from the (e, e^?K⁺) Cross Section

by Omar Benhar

Particles 2021, 4(2), 194-204; https://doi.org/10.3390/particles4020018 - 11 May 2021

Viewed by 2239

Abstract

Experimental studies of hypernuclear dynamics, besides being essential for the understanding of strong interactions in the strange sector, have important astrophysical implications. The observation of neutron stars with masses exceeding two solar masses poses a serious challenge to the models of hyperon dynamics [...] Read more.

Experimental studies of hypernuclear dynamics, besides being essential for the understanding of strong interactions in the strange sector, have important astrophysical implications. The observation of neutron stars with masses exceeding two solar masses poses a serious challenge to the models of hyperon dynamics in dense nuclear matter, many of which predict a maximum mass incompatible with the data. In this paper, it is argued that valuable new insight can be gained from the forthcoming extension of the experimental studies of kaon electro production from nuclei to include the

^{208} Pb (e, e^{?} K^{+})_{?}^{208} Tl

process. A comprehensive framework for the description of kaon electro production, based on factorization of the nuclear cross section and the formalism of the nuclear many-body theory, is outlined. This approach highlights the connection between the kaon production and proton knockout reactions, which will allow us to exploit the available

^{208} Pb (e, e^{?} p)^{207} Tl

data to achieve a largely model-independent analysis of the measured cross section. Full article

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19 pages, 3341 KiB

Open AccessEditor’s ChoiceArticle

Quarkonia Formation in a Holographic Gravity–Dilaton Background Describing QCD Thermodynamics

by Rico Zöllner and Burkhard Kämpfer

Particles 2021, 4(2), 159-177; https://doi.org/10.3390/particles4020015 - 6 Apr 2021

Cited by 12 | Viewed by 4620

Abstract

A holographic model of probe quarkonia is presented, where the dynamical gravity–dilaton background was adjusted to the thermodynamics of 2 + 1 flavor QCD with physical quark masses. The quarkonia action was modified to account for the systematic study of the heavy-quark mass [...] Read more.

A holographic model of probe quarkonia is presented, where the dynamical gravity–dilaton background was adjusted to the thermodynamics of 2 + 1 flavor QCD with physical quark masses. The quarkonia action was modified to account for the systematic study of the heavy-quark mass dependence. We focused on the

J / ?

and

?

spectral functions and related our model to heavy quarkonia formation as a special aspect of hadron phenomenology in heavy-ion collisions at LHC. Full article

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12 pages, 1306 KiB

Open AccessEditor’s ChoiceConference Report

Transport Properties in Magnetized Compact Stars

by Toshitaka Tatsumi and Hiroaki Abuki

Particles 2021, 4(1), 63-74; https://doi.org/10.3390/particles4010009 - 21 Feb 2021

Viewed by 2396

Abstract

Transport properties of dense quark matter are discussed in the strong magnetic field, B. B dependence as well as density dependence of the Hall conductivity is discussed, based on the microscopic Kubo formula. We took into account the possibility of the inhomogeneous [...] Read more.

Transport properties of dense quark matter are discussed in the strong magnetic field, B. B dependence as well as density dependence of the Hall conductivity is discussed, based on the microscopic Kubo formula. We took into account the possibility of the inhomogeneous chiral phase at moderate densities, where anomalous Hall effect is intrinsic and resembles the one in Weyl semimetals in condensed matter physics. Some theoretical aspects inherent in anomalous Hall effect are also discussed. Full article

(This article belongs to the Special Issue Selected Papers from “The Modern Physics of Compact Stars and Relativistic Gravity 2019”)

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6 pages, 288 KiB

Open AccessEditor’s ChoiceConference Report

Deep Learning Based Impact Parameter Determination for the CBM Experiment

by Manjunath Omana Kuttan, Jan Steinheimer, Kai Zhou, Andreas Redelbach and Horst Stoecker

Particles 2021, 4(1), 47-52; https://doi.org/10.3390/particles4010006 - 2 Feb 2021

Cited by 13 | Viewed by 3602

Abstract

In this talk we presented a novel technique, based on Deep Learning, to determine the impact parameter of nuclear collisions at the CBM experiment. PointNet based Deep Learning models are trained on UrQMD followed by CBMRoot simulations of Au+Au collisions at 10 A [...] Read more.

In this talk we presented a novel technique, based on Deep Learning, to determine the impact parameter of nuclear collisions at the CBM experiment. PointNet based Deep Learning models are trained on UrQMD followed by CBMRoot simulations of Au+Au collisions at 10 AGeV to reconstruct the impact parameter of collisions from raw experimental data such as hits of the particles in the detector planes, tracks reconstructed from the hits or their combinations. The PointNet models can perform fast, accurate, event-by-event impact parameter determination in heavy ion collision experiments. They are shown to outperform a simple model which maps the track multiplicity to the impact parameter. While conventional methods for centrality classification merely provide an expected impact parameter distribution for a given centrality class, the PointNet models predict the impact parameter from 2–14 fm on an event-by-event basis with a mean error of ?0.33 to 0.22 fm. Full article

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

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13 pages, 673 KiB

Open AccessEditor’s ChoiceArticle

Spin Susceptibility in Neutron Matter from Quantum Monte Carlo Calculations

by Luca Riz, Francesco Pederiva, Diego Lonardoni and Stefano Gandolfi

Particles 2020, 3(4), 706-718; https://doi.org/10.3390/particles3040046 - 26 Nov 2020

Cited by 3 | Viewed by 3546

Abstract

The spin susceptibility in pure neutron matter is computed from auxiliary field diffusion Monte Carlo calculations over a wide range of densities. The calculations are performed for different spin asymmetries, while using twist-averaged boundary conditions to reduce finite-size effects. The employed nuclear interactions [...] Read more.

The spin susceptibility in pure neutron matter is computed from auxiliary field diffusion Monte Carlo calculations over a wide range of densities. The calculations are performed for different spin asymmetries, while using twist-averaged boundary conditions to reduce finite-size effects. The employed nuclear interactions include both the phenomenological Argonne AV8′ + UIX potential and local interactions that are derived from chiral effective field theory up to next-to-next-to-leading order. Full article

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9 pages, 624 KiB

Open AccessEditor’s ChoiceArticle

A Bayesian Analysis on Neutron Stars within Relativistic Mean Field Models

by Prasanta Char, Silvia Traversi and Giuseppe Pagliara

Particles 2020, 3(3), 621-629; https://doi.org/10.3390/particles3030040 - 7 Aug 2020

Cited by 5 | Viewed by 2979

Abstract

We present a Bayesian analysis on the equation of state of neutron stars based on a class of relativistic mean field models. The priors on the equation of state are related to the properties of nuclear matter at saturation and the posteriors are [...] Read more.

We present a Bayesian analysis on the equation of state of neutron stars based on a class of relativistic mean field models. The priors on the equation of state are related to the properties of nuclear matter at saturation and the posteriors are obtained through the Bayesian procedure by exploiting recent astrophysical constraints on the mass–radius relations of neutron stars. We find indications of a tension (within the adopted model) between the prior on the nuclear incompressibility and its posterior which in turn seems to suggest a possible phase transition at about twice saturation density to a phase where the nucleon effective mass is strongly reduced. A possible relation with the chiral phase transition in dense matter is also discussed. Full article

(This article belongs to the Special Issue Selected Papers from “The Modern Physics of Compact Stars and Relativistic Gravity 2019”)

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19 pages, 326 KiB

Open AccessEditor’s ChoiceTutorial

Gauge Dependence of the Gauge Boson Projector

by Priidik Gallagher, Stefan Groote and Maria Naeem

Particles 2020, 3(3), 543-561; https://doi.org/10.3390/particles3030037 - 28 Jul 2020

Cited by 4 | Viewed by 2985

Abstract

The propagator of a gauge boson, like the massless photon or the massive vector bosons

W^{\pm}

and Z of the electroweak theory, can be derived in two different ways, namely via Green’s functions (semi-classical approach) or via the vacuum expectation value of [...] Read more.

The propagator of a gauge boson, like the massless photon or the massive vector bosons

W^{\pm}

and Z of the electroweak theory, can be derived in two different ways, namely via Green’s functions (semi-classical approach) or via the vacuum expectation value of the time-ordered product of the field operators (field theoretical approach). Comparing the semi-classical with the field theoretical approach, the central tensorial object can be defined as the gauge boson projector, directly related to the completeness relation for the complete set of polarisation four-vectors. In this paper we explain the relation for this projector to different cases of the

R_{ξ}

gauge and explain why the unitary gauge is the default gauge for massive gauge bosons. Full article

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11 pages, 750 KiB

Open AccessEditor’s ChoiceArticle

Neutron Stars in f(R)-Gravity and Its Extension with a Scalar Axion Field

by Artyom Astashenok and Sergey Odintsov

Particles 2020, 3(3), 532-542; https://doi.org/10.3390/particles3030036 - 1 Jul 2020

Cited by 6 | Viewed by 3025

Abstract

We present a brief review of general results about non-rotating neutron stars in simple

R^{2}

gravity and its extension with a scalar axion field. Modified Einstein equations are presented for metrics in isotropical coordinates. The mass–radius relation, mass profile and dependence of [...] Read more.

We present a brief review of general results about non-rotating neutron stars in simple

R^{2}

gravity and its extension with a scalar axion field. Modified Einstein equations are presented for metrics in isotropical coordinates. The mass–radius relation, mass profile and dependence of mass from central density on various equations of state are given in comparison to general relativity. Full article

(This article belongs to the Special Issue Selected Papers from “The Modern Physics of Compact Stars and Relativistic Gravity 2019”)

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10 pages, 381 KiB

Open AccessEditor’s ChoiceConference Report

Critical Behavior of (2 + 1)-Dimensional QED: 1/N Expansion

by Anatoly V. Kotikov and Sofian Teber

Particles 2020, 3(2), 345-354; https://doi.org/10.3390/particles3020026 - 10 Apr 2020

Cited by 29 | Viewed by 2935

Abstract

We present recent results on dynamical chiral symmetry breaking in (2 + 1)-dimensional QED with N four-component fermions. The results of the

1 / N

expansion in the leading and next-to-leading orders were found exactly in an arbitrary nonlocal gauge. [...] Read more.

We present recent results on dynamical chiral symmetry breaking in (2 + 1)-dimensional QED with N four-component fermions. The results of the

1 / N

expansion in the leading and next-to-leading orders were found exactly in an arbitrary nonlocal gauge. Full article

(This article belongs to the Special Issue Selected Papers from “Theory of Hadronic Matter under Extreme Conditions”)

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16 pages, 4747 KiB

Open AccessEditor’s ChoiceArticle

Astrophysics in the Laboratory—The CBM Experiment at FAIR

by Peter Senger

Particles 2020, 3(2), 320-335; https://doi.org/10.3390/particles3020024 - 2 Apr 2020

Cited by 7 | Viewed by 3833

Abstract

The future “Facility for Antiproton and Ion Research” (FAIR) is an accelerator-based international center for fundamental and applied research, which presently is under construction in Darmstadt, Germany. An important part of the program is devoted to questions related to astrophysics, including the origin [...] Read more.

The future “Facility for Antiproton and Ion Research” (FAIR) is an accelerator-based international center for fundamental and applied research, which presently is under construction in Darmstadt, Germany. An important part of the program is devoted to questions related to astrophysics, including the origin of elements in the universe and the properties of strongly interacting matter under extreme conditions, which are relevant for our understanding of the structure of neutron stars and the dynamics of supernova explosions and neutron star mergers. The Compressed Baryonic Matter (CBM) experiment at FAIR is designed to measure promising observables in high-energy heavy-ion collisions, which are expected to be sensitive to the high-density equation-of-state (EOS) of nuclear matter and to new phases of Quantum Chromo Dynamics (QCD) matter at high densities. The CBM physics program, the relevant observables and the experimental setup will be discussed. Full article

(This article belongs to the Special Issue Selected Papers from “The Modern Physics of Compact Stars and Relativistic Gravity 2019”)

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30 pages, 1271 KiB

Open AccessEditor’s ChoiceArticle

A Study of the Properties of the QCD Phase Diagram in High-Energy Nuclear Collisions

by Xiaofeng Luo, Shusu Shi, Nu Xu and Yifei Zhang

Particles 2020, 3(2), 278-307; https://doi.org/10.3390/particles3020022 - 1 Apr 2020

Cited by 47 | Viewed by 5754

Abstract

With the aim of understanding the phase structure of nuclear matter created in high-energy nuclear collisions at finite baryon density, a beam energy scan program has been carried out at Relativistic Heavy Ion Collider (RHIC). In this mini-review, most recent experimental results on [...] Read more.

With the aim of understanding the phase structure of nuclear matter created in high-energy nuclear collisions at finite baryon density, a beam energy scan program has been carried out at Relativistic Heavy Ion Collider (RHIC). In this mini-review, most recent experimental results on collectivity, criticality and heavy flavor productions will be discussed. The goal here is to establish the connection between current available data and future heavy-ion collision experiments in a high baryon density region. Full article

(This article belongs to the Special Issue Relativistic and Ultrarelativistic Nuclear Collisions: Dynamics and Phase Transitions)

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27 pages, 500 KiB

Open AccessEditor’s ChoiceReview

Effective Field Theories

by Andrey Grozin

Particles 2020, 3(2), 245-271; https://doi.org/10.3390/particles3020020 - 31 Mar 2020

Cited by 5 | Viewed by 2971

Abstract

This paper represents a pedagogical introduction to low-energy effective field theories. In some of them, heavy particles are “integrated out” (a typical example—the Heisenberg–Euler EFT); in some, heavy particles remain but some of their degrees of freedom are “integrated out” (Bloch–Nordsieck EFT). A [...] Read more.

This paper represents a pedagogical introduction to low-energy effective field theories. In some of them, heavy particles are “integrated out” (a typical example—the Heisenberg–Euler EFT); in some, heavy particles remain but some of their degrees of freedom are “integrated out” (Bloch–Nordsieck EFT). A large part of these lectures is, technically, in the framework of QED. QCD examples, namely decoupling of heavy flavors and HQET, are discussed only briefly. However, effective field theories of QCD are very similar to the QED case, and there are just some small technical complications: more diagrams, color factors, etc. The method of regions provides an alternative view at low-energy effective theories; this is also briefly introduced. Full article

(This article belongs to the Special Issue Quantum Field Theory at the Limits: From Strong Fields to Heavy Quarks)

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15 pages, 680 KiB

Open AccessEditor’s ChoiceArticle

Semileptonic Decays of Heavy Baryons in the Relativistic Quark Model

by Rudolf N. Faustov and Vladimir O. Galkin

Particles 2020, 3(1), 208-222; https://doi.org/10.3390/particles3010017 - 6 Mar 2020

Cited by 7 | Viewed by 2750

Abstract

Semileptonic and rare semileptonic decays of heavy baryons are studied in the framework of the relativistic quark model based on the quark-diquark picture, quasipotential approach, and quantum chromodynamics (QCD). The form factors parametrizing the matrix elements of the weak transitions are calculated in [...] Read more.

Semileptonic and rare semileptonic decays of heavy baryons are studied in the framework of the relativistic quark model based on the quark-diquark picture, quasipotential approach, and quantum chromodynamics (QCD). The form factors parametrizing the matrix elements of the weak transitions are calculated in the whole accessible kinematical range with the comprehensive account of the relativistic effects. The obtained results for the branching ratios and other observables agree well with the available experimental data. Full article

(This article belongs to the Special Issue Quantum Field Theory at the Limits: From Strong Fields to Heavy Quarks)

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5 pages, 407 KiB

Open AccessEditor’s ChoiceConference Report

The DsTau Experiment: A Study for Tau-Neutrino Production

by Mădălina Mihaela Miloi and [DsTau Collaboration]

Particles 2020, 3(1), 164-168; https://doi.org/10.3390/particles3010013 - 1 Mar 2020

Viewed by 2826

Abstract

For clarifying the validity of the Lepton Universality hypothesis, one of the fundamental statements of the Standard Model, the interaction cross section for all three flavors of leptons have to be known with high precision. In neutrino sector, for electron and muon neutrinos, [...] Read more.

For clarifying the validity of the Lepton Universality hypothesis, one of the fundamental statements of the Standard Model, the interaction cross section for all three flavors of leptons have to be known with high precision. In neutrino sector, for electron and muon neutrinos, the interaction cross section is known fairly well, but for tau neutrino only poor estimations exist. In particular, the most direct measurement by the DONuT experiment was performed with rather poor accuracy due to low statistics and an uncertainty of the tau neutrino flux. The DsTau experiment proposes to study tau-neutrino production process and thus to improve significantly the accuracy of calculations of tau neutrino flux for neutrino accelerator experiments. To study reactions providing most of tau neutrinos, the experiment uses a setup based on high resolution nuclear emulsions, capable to register short lived particle decays created in proton-nucleus interactions. The present report is an overview of the DsTau experiment together with some of the preliminary results from the pilot run. Full article

(This article belongs to the Special Issue Quantum Field Theory at the Limits: From Strong Fields to Heavy Quarks)

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15 pages, 474 KiB

Open AccessEditor’s ChoiceArticle

Analytic Properties of Triangle Feynman Diagrams in Quantum Field Theory

by Dmitri Melikhov

Particles 2020, 3(1), 99-113; https://doi.org/10.3390/particles3010009 - 12 Feb 2020

Cited by 1 | Viewed by 3691

Abstract

We discuss dispersion representations for the triangle diagram

F (q^{2}, p_{1}^{2}, p_{2}^{2})

, the single dispersion representation in

q^{2}

and the double dispersion representation in

p_{1}^{2}

and

p_{2}^{2}

, [...] Read more.

We discuss dispersion representations for the triangle diagram

F (q^{2}, p_{1}^{2}, p_{2}^{2})

, the single dispersion representation in

q^{2}

and the double dispersion representation in

p_{1}^{2}

and

p_{2}^{2}

, with special emphasis on the appearance of the anomalous singularities and the anomalous cuts in these representations. Full article

(This article belongs to the Special Issue Quantum Field Theory at the Limits: From Strong Fields to Heavy Quarks)

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23 pages, 527 KiB

Open AccessEditor’s ChoiceReview

Probing Vacuum Polarization Effects with High-Intensity Lasers

by Felix Karbstein

Particles 2020, 3(1), 39-61; https://doi.org/10.3390/particles3010005 - 19 Jan 2020

Cited by 52 | Viewed by 4755

Abstract

These notes provide a pedagogical introduction to the theoretical study of vacuum polarization effects in strong electromagnetic fields as provided by state-of-the-art high-intensity lasers. Quantum vacuum fluctuations give rise to effective couplings between electromagnetic fields, thereby supplementing Maxwell’s linear theory of classical electrodynamics [...] Read more.

These notes provide a pedagogical introduction to the theoretical study of vacuum polarization effects in strong electromagnetic fields as provided by state-of-the-art high-intensity lasers. Quantum vacuum fluctuations give rise to effective couplings between electromagnetic fields, thereby supplementing Maxwell’s linear theory of classical electrodynamics with nonlinearities. Resorting to a simplified laser pulse model, allowing for explicit analytical insights, we demonstrate how to efficiently analyze all-optical signatures of these effective interactions in high-intensity laser experiments. Moreover, we highlight several key features relevant for the accurate planning and quantitative theoretical analysis of quantum vacuum nonlinearities in the collision of high-intensity laser pulses. Full article

(This article belongs to the Special Issue Quantum Field Theory at the Limits: From Strong Fields to Heavy Quarks)

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8 pages, 236 KiB

Open AccessEditor’s ChoiceArticle

Chiral Perturbation Theory vs. Linear Sigma Model in a Chiral Imbalance Medium

by Alexander Andrianov, Vladimir Andrianov and Domenec Espriu

Particles 2020, 3(1), 15-22; https://doi.org/10.3390/particles3010002 - 8 Jan 2020

Cited by 17 | Viewed by 2752

Abstract

We compare the chiral perturbation theory (ChPT) and the linear sigma model (LSM) as realizations of low energy quantum chromodynamics (QCD) for light mesons in a chirally-imbalanced medium. The relations between the low-energy constants of the chiral Lagrangian and the corresponding constants of [...] Read more.

We compare the chiral perturbation theory (ChPT) and the linear sigma model (LSM) as realizations of low energy quantum chromodynamics (QCD) for light mesons in a chirally-imbalanced medium. The relations between the low-energy constants of the chiral Lagrangian and the corresponding constants of the linear sigma model are established as well as the expressions for the decay constant of

π

-meson in the medium and for the mass of the

a_{0}

. In the large

N_{c}

count taken from QCD the correspondence of ChPT and LSM is remarkably good and provides a solid ground for the search of chiral imbalance manifestations in pion physics. A possible experimental detection of chiral imbalance (and therefore a phase with local parity breaking) is outlined in the charged pion decays inside the fireball. Full article

(This article belongs to the Special Issue Selected Papers from “Theory of Hadronic Matter under Extreme Conditions”)

14 pages, 312 KiB

Open AccessEditor’s ChoiceArticle

Calculation of Acceleration Effects Using the Zubarev Density Operator

by Georgy Prokhorov, Oleg Teryaev and Valentin Zakharov

Particles 2020, 3(1), 1-14; https://doi.org/10.3390/particles3010001 - 3 Jan 2020

Cited by 10 | Viewed by 2699

Abstract

The relativistic form of the Zubarev density operator can be used to study quantum effects associated with acceleration of the medium. In particular, it was recently shown that the calculation of perturbative corrections in acceleration based on the Zubarev density operator makes it [...] Read more.

The relativistic form of the Zubarev density operator can be used to study quantum effects associated with acceleration of the medium. In particular, it was recently shown that the calculation of perturbative corrections in acceleration based on the Zubarev density operator makes it possible to show the existence of the Unruh effect. In this paper, we present the details of the calculation of quantum correlators arising in the fourth order of the perturbation theory needed to demonstrate the Unruh effect. Expressions for the quantum corrections for massive fermions are also obtained. Full article

(This article belongs to the Special Issue Nonequilibrium Phenomena in Strongly Correlated Systems)

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