Research

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11 pages, 589 KiB

Open AccessFeature PaperArticle

Study of Corrections for Anomalous Coupling Limits Due to the Possible Background BSM Contributions

by Artur E. Semushin and Evgeny Yu. Soldatov

Symmetry 2022, 14(10), 2082; https://0-doi-org.brum.beds.ac.uk/10.3390/sym14102082 - 06 Oct 2022

Viewed by 1064

The search for anomalous couplings is one of the possible ways to find any deviations from the Standard Model. Effective field theory is used to parameterize the anomalous couplings in the Lagrangian with operators of higher dimensions constructed from the SM fields. In [...] Read more.

The search for anomalous couplings is one of the possible ways to find any deviations from the Standard Model. Effective field theory is used to parameterize the anomalous couplings in the Lagrangian with operators of higher dimensions constructed from the SM fields. In the classical way, the limits on the Wilson coefficients of these operators are set based on beyond the Standard Model contributions induced for the signal process, whereas the ones induced for background processes are assumed to be negligible. This article provides a study of the corrections to the limits on Wilson coefficients by considering beyond the Standard Model contributions induced for background processes. The studies of

Z (ν \bar{ν}) γ j j

and

W (ℓ ν) γ j j

productions in

p p

collisions with

\sqrt{s} = 13

TeV and conditions of the ATLAS experiment at the LHC are used as an example. Cases with integrated luminosity collected during Run II of 139 fb

^{- 1}

and expected from Run III of 300 fb

^{- 1}

are considered. The expected 95% CL limits on coefficients

f_{T 0} / Λ^{4}

,

f_{T 5} / Λ^{4}

,

f_{M 0} / Λ^{4}

and

f_{M 2} / Λ^{4}

are obtained both in the classical way and in the way, where the corrections from background anomalous contributions are applied. Corrected one-dimensional limits from

Z (ν \bar{ν}) γ j j

and

W (ℓ ν) γ j j

productions are up to 9.1% and 4.4% (depending on the operator) tighter than the classical ones, respectively. Corrected combined limits are up to 3.0% (depending on the operator) tighter than the classical ones. Corrections to two-dimensional limits are also obtained. The corrected contours are more stringent compared with the classical ones, and the maximal improvement is 17.2%. Full article

(This article belongs to the Special Issue QCD- and QED-Like Theories and Symmetry)

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16 pages, 641 KiB

Open AccessArticle

Persistent Homology Analysis for Dense QCD Effective Model with Heavy Quarks

by Kouji Kashiwa, Takehiro Hirakida and Hiroaki Kouno

Symmetry 2022, 14(9), 1783; https://0-doi-org.brum.beds.ac.uk/10.3390/sym14091783 - 26 Aug 2022

Cited by 9 | Viewed by 1227

Abstract

The isospin chemical potential region is known as the sign-problem-free region of quantum chromodynamics (QCD). In this paper, we introduce the isospin chemical potential to the three-dimensional three-state Potts model to mimic dense QCD; e.g., the QCD effective model with heavy quarks at [...] Read more.

The isospin chemical potential region is known as the sign-problem-free region of quantum chromodynamics (QCD). In this paper, we introduce the isospin chemical potential to the three-dimensional three-state Potts model to mimic dense QCD; e.g., the QCD effective model with heavy quarks at finite density. We call it the QCD-like Potts model. The QCD-like Potts model does not have a sign problem, but we expect it to share some properties with QCD. Since we can obtain the non-approximated Potts spin configuration at finite isospin chemical potential, where the simple Metropolis algorithm can work, we perform the persistent homology analysis toward exploring the dense spatial structure of QCD. We show that the averaged birth-death ratio has the same information with the Polyakov loop, but the maximum birth-death ratio has additional information near the phase transition where the birth-death ratio means the ratio of the creation time of a hole and its vanishing time based on the persistent homology. Full article

(This article belongs to the Special Issue QCD- and QED-Like Theories and Symmetry)

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16 pages, 1114 KiB

Open AccessArticle

Quark Self-Energy and Condensates in NJL Model with External Magnetic Field

by Juan Liu, Yilun Du and Song Shi

Symmetry 2021, 13(8), 1410; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13081410 - 02 Aug 2021

Cited by 1 | Viewed by 1433

Abstract

In a one-flavor NJL model with a finite temperature, chemical potential, and external magnetic field, the self-energy of the quark propagator contains more condensates besides the vacuum condensate. We use Fierz identity to identify the self-energy and propose a self-consistent analysis to simplify [...] Read more.

In a one-flavor NJL model with a finite temperature, chemical potential, and external magnetic field, the self-energy of the quark propagator contains more condensates besides the vacuum condensate. We use Fierz identity to identify the self-energy and propose a self-consistent analysis to simplify it. It turns out that these condensates are related to the chiral separation effect and spin magnetic moment. Full article

(This article belongs to the Special Issue QCD- and QED-Like Theories and Symmetry)

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13 pages, 336 KiB

Open AccessArticle

Investigation of the Thermal QCD Matter from Canonical Sectors

by Kouji Kashiwa

Symmetry 2021, 13(7), 1273; https://0-doi-org.brum.beds.ac.uk/10.3390/sym13071273 - 15 Jul 2021

Cited by 2 | Viewed by 1549

Abstract

We discuss the thermal phase structure of quantum chromodynamics (QCD) at zero real chemical potential (

μ_{R} = 0

) from the viewpoint of canonical sectors. The canonical sectors take the system to pieces of each elementary excitation mode and thus seem [...] Read more.

We discuss the thermal phase structure of quantum chromodynamics (QCD) at zero real chemical potential (

μ_{R} = 0

) from the viewpoint of canonical sectors. The canonical sectors take the system to pieces of each elementary excitation mode and thus seem to be useful in the investigation of the confinement–deconfinement nature of QCD. Since the canonical sectors themselves are difficult to compute, we propose a convenient quantity which may determine the structural changes of the canonical sectors. We discuss the quantity qualitatively by adopting lattice QCD prediction for the phase structure with finite imaginary chemical potential. In addition, we numerically estimate this quantity by using the simple QCD effective model. It is shown that there should be a sharp change of the canonical sectors near the Roberge–Weiss endpoint temperature at

μ_{R} = 0

. Then, the behavior of the quark number density at finite imaginary chemical potential plays a crucial role in clarifying the thermal QCD properties. Full article

(This article belongs to the Special Issue QCD- and QED-Like Theories and Symmetry)

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9 pages, 309 KiB

Open AccessArticle

Constraints on the Anomalous Wtb Couplings from B-Physics Experiments

by Anastasiia Kozachuk and Dmitri Melikhov

Symmetry 2020, 12(9), 1506; https://0-doi-org.brum.beds.ac.uk/10.3390/sym12091506 - 14 Sep 2020

Cited by 3 | Viewed by 1332

Abstract

We analyze constraints on the anomalous

W t b

couplings from B-physics experiments, performing a correlated analysis and allowing all anomalous couplings to differ simultaneously from their Standard Model (SM) values. The B-physics observables allow one to probe three linear combinations [...] Read more.

We analyze constraints on the anomalous

W t b

couplings from B-physics experiments, performing a correlated analysis and allowing all anomalous couplings to differ simultaneously from their Standard Model (SM) values. The B-physics observables allow one to probe three linear combinations out of the four anomalous couplings, which parameterize the

W t b

vertex under the assumption that the SM symmetries remain the symmetries of the effective theory. The constraints in this work are obtained by taking into account the following B-physics observables: the

{\bar{B}}^{0} - B^{0}

oscillations, the leptonic

B \to μ^{+} μ^{-}

decays, the inclusive radiative

B \to X_{s} γ

decays, and the differential branching fractions in the semileptonic inclusive

B \to X_{s} μ^{+} μ^{-}

and exclusive

B \to (K, K^{*}) μ^{+} μ^{-}

decays at small

q^{2}

, with q the momentum of the

μ^{+} μ^{-}

pair. We find that the SM values of the anomalous couplings belong to the 95% CL allowed region obtained this way, but lie beyond the 68% allowed region. We also report that the distributions of the anomalous couplings obtained within our scenario differ from the results of the 1D scenario, when only one of the couplings is allowed to deviate from its SM value. Full article

(This article belongs to the Special Issue QCD- and QED-Like Theories and Symmetry)

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17 pages, 450 KiB

Open AccessArticle

Quasielastic Lepton Scattering off Two-Component Dark Matter in Hypercolor Model

by Vitaly Beylin, Maxim Bezuglov, Vladimir Kuksa and Egor Tretiakov

Symmetry 2020, 12(5), 708; https://0-doi-org.brum.beds.ac.uk/10.3390/sym12050708 - 02 May 2020

Cited by 4 | Viewed by 1638

Abstract

The interaction of high-energy leptons with components of Dark Matter in a hypercolor model is considered. The possibility of detection, using IceCube secondary neutrinos produced by quasielastic scattering of cosmic ray electrons off hidden mass particles, is investigated. The dominant contribution to the [...] Read more.

The interaction of high-energy leptons with components of Dark Matter in a hypercolor model is considered. The possibility of detection, using IceCube secondary neutrinos produced by quasielastic scattering of cosmic ray electrons off hidden mass particles, is investigated. The dominant contribution to the cross section results from diagrams with scalar exchanges. A strong dependence of the total cross section on the Dark Matter components mass is also found. Full article

(This article belongs to the Special Issue QCD- and QED-Like Theories and Symmetry)

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9 pages, 248 KiB

Open AccessFeature PaperArticle

Interaction of Hadronic Dark Matter with Nucleons and Leptons

by Vitaly Beylin and Vladimir Kuksa

Symmetry 2020, 12(4), 567; https://0-doi-org.brum.beds.ac.uk/10.3390/sym12040567 - 05 Apr 2020

Cited by 3 | Viewed by 1632

Abstract

We analyze the low-energy Lagrangian of hadronic dark matter interaction with nucleons and leptons. The analysis was fulfilled within the framework of the effective meson-exchange model, which is based on dynamic realization of SU(3)-symmetry. Using this Lagrangian, we calculate the cross-section of [...] Read more.

We analyze the low-energy Lagrangian of hadronic dark matter interaction with nucleons and leptons. The analysis was fulfilled within the framework of the effective meson-exchange model, which is based on dynamic realization of SU(3)-symmetry. Using this Lagrangian, we calculate the cross-section of low-energy scattering of nucleons on hadronic dark matter particles. Effective vertex of W-boson interaction with new hadrons is constructed and the cross-section of lepton scattering on dark matter particles is calculated. Full article

(This article belongs to the Special Issue QCD- and QED-Like Theories and Symmetry)

Review

Jump to: Research

10 pages, 1103 KiB

Open AccessFeature PaperReview

From the Early Universe to the Modern Universe

by V. V. Burdyuzha

Symmetry 2020, 12(3), 382; https://0-doi-org.brum.beds.ac.uk/10.3390/sym12030382 - 03 Mar 2020

Cited by 1 | Viewed by 2085

Abstract

The birth of the Universe, its dark components, and the next fundamental level of matter are briefly discussed. The classical cosmological solution for our Universe with a Λ-term has two branches divided by a gap. The quantum process of tunneling between branches took [...] Read more.

The birth of the Universe, its dark components, and the next fundamental level of matter are briefly discussed. The classical cosmological solution for our Universe with a Λ-term has two branches divided by a gap. The quantum process of tunneling between branches took place. A model of a slowly swelling Universe in the result of the multiple reproductions of cosmological cycles arises naturally. The occurrence of baryon asymmetry is briefly discussed. The problem of the cosmological constant is solved and, thus, the crisis of physics connected with this constant is overcome. But we note that dark energy is evolving. Dark matter (part or all) consists of familon-type pseudo-Goldstone bosons with a mass of 10⁻⁵–10⁻³ eV. It follows the composite model of particles. This model reproduces three relativistic phase transitions in the medium of familons at different red shifts, forming a large scale structure of the Universe dark matter that was “repeated” by baryons. Here three generations of elementary particles are absolutely necessary. Full article

(This article belongs to the Special Issue QCD- and QED-Like Theories and Symmetry)

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