scholarly journals Symmetries and Their Breaking in the Fundamental Laws of Physics

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1316
Author(s):  
Jose Bernabeu
Keyword(s):  
Gauge Symmetry ◽  
Particle Physics ◽  
Weak Interactions ◽  
Neutral Current ◽  
Laws Of Nature ◽  
New Physics ◽  
Standard Theory ◽  
Strong Interactions ◽  
Neutral Mesons ◽  
Local Gauge Symmetry

Symmetries in the Physical Laws of Nature lead to observable effects. Beyond the regularities and conserved magnitudes, the last few decades in particle physics have seen the identification of symmetries, and their well-defined breaking, as the guiding principle for the elementary constituents of matter and their interactions. Flavour SU(3) symmetry of hadrons led to the Quark Model and the antisymmetric requirement under exchange of identical fermions led to the colour degree of freedom. Colour became the generating charge for flavour-independent strong interactions of quarks and gluons in the exact colour SU(3) local gauge symmetry. Parity Violation in weak interactions led us to consider the chiral fields of fermions as the objects with definite transformation properties under the weak isospin SU(2) gauge group of the Unifying Electro-Weak SU(2) × U(1) symmetry, which predicted novel weak neutral current interactions. CP-Violation led to three families of quarks opening the field of Flavour Physics. Time-reversal violation has recently been observed with entangled neutral mesons, compatible with CPT-invariance. The cancellation of gauge anomalies, which would invalidate the gauge symmetry of the quantum field theory, led to Quark–Lepton Symmetry. Neutrinos were postulated in order to save the conservation laws of energy and angular momentum in nuclear beta decay. After the ups and downs of their mass, neutrino oscillations were discovered in 1998, opening a new era about their origin of mass, mixing, discrete symmetries and the possibility of global lepton-number violation through Majorana mass terms and Leptogenesis as the source of the matter–antimatter asymmetry in the universe. The experimental discovery of quarks and leptons and the mediators of their interactions, with physical observables in spectacular agreement with this Standard Theory, is the triumph of Symmetries. The gauge symmetry is exact only when the particles are massless. One needs a subtle breaking of the symmetry, providing the origin of mass without affecting the excellent description of the interactions. This is the Brout–Englert–Higgs Mechanism, which produces the Higgs Boson as a remnant, discovered at CERN in 2012. Open present problems are addressed with by searching the New Physics Beyond-the-Standard-Model.

scholarly journals Search for Charged Lepton Flavour Violation at CMS

2018 ◽  
Vol 182 ◽  
pp. 02090
Author(s):  
Swagata Mukherjee
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Particle Physics ◽  
Charged Lepton ◽  
New Physics ◽  
Lepton Sector ◽  
Lepton Flavour Violation ◽  
The Standard Model ◽  
Flavour Violation ◽  
Lepton Flavour

Lepton flavour is a conserved quantity in the standard model of particle physics, but it does not follow from an underlying gauge symmetry. After the discovery of neutrino oscillation, it has been established that lepton flavour is not conserved in the neutral sector. Thus the lepton sector is an excellent place to look for New Physics, and in this perspective the Charged Lepton Flavour Violation is interesting. Various extensions of the standard model predict lepton flavour violating decays that can be observed at LHC. This report summarises several searches for lepton flavour violation with data collected by the CMS detector.

Unification of Strong-Weak Interactions and Possible Unified Scheme of Four-Interactions

2020 ◽  
Vol 8 (5) ◽  
Author(s):  
Yi-Fang Chang
Keyword(s):  
Particle Physics ◽  
Short Range ◽  
Weak Interactions ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Coupling Constants ◽  
Strong Interactions ◽  
Main Character ◽  
Unified Theories ◽  
Three Dimensional Space

First, various known unified theories of interactions in particle physics are reviewed. Next, strong and weak interactions are all short-range, which should more be unified. Except different action ranges their main character is: strong interactions are attraction each other, and weak interactions are mutual repulsion and derive decay. We propose a possible method on their unification, whose coupling constants are negative and positive, respectively. Further, we propose a figure on the unification of the four basic interactions in three-dimensional space, and search some possible tests and predictions, for example, strong-weak interactions transform each other, some waves may be produced. Finally, based on the simplest unified gauge group GL(6,C) of four-interactions, a possible form of Lagrangian is researched. Some relations and equations of different interactions are discussed.

scholarly journals William James Stirling CBE. 4 February 1953—9 November 2018

2019 ◽  
Vol 68 ◽  
pp. 385-406
Author(s):  
A. D. Martin ◽  
B. R. Webber
Keyword(s):  
Particle Physics ◽  
William James ◽  
Vector Boson ◽  
New Physics ◽  
Strong Interactions ◽  
Cavendish Laboratory ◽  
Vice Chancellor ◽  
Theoretical Predictions ◽  
Personal Qualities ◽  
Gluon Distributions

James Stirling's wide-ranging contributions to the development and application of quantum chromodynamics were central in verifying QCD as the correct theory of strong interactions, and in computing precise predictions for all types of collider processes. He published more than 300 papers on a vast range of phenomenological topics, including some of the most highly cited of all time in particle physics. His research, always full of insight, focused on the confrontation of theoretical predictions with experimental results. Amongst many key contributions, he developed the helicity amplitude method and used it to show that the CERN ‘monojet’ events, thought to be a possible signal of new physics, were due to vector boson plus jet production. The method has since facilitated the calculation of many other important processes. At Durham he formed a famous long-standing collaboration that set the standard for determining the quark and gluon distributions in the proton. Besides his intellectual brilliance, his personal qualities of humility, modesty, diligence and fairness made him an outstanding scientific leader and administrator. He played a major role in the foundation of the Institute for Particle Physics Phenomenology in Durham and served as its first Director. In 2005 he was appointed Pro-Vice Chancellor for Research at Durham. He moved to the Cavendish Laboratory in Cambridge in 2008, becoming Head of the Department of Physics in 2011. Then in 2013 he was appointed to the newly created position of Provost, the chief academic officer, at Imperial College, London, from which he retired in August 2018.

scholarly journals A bottom-up approach to the strong CP problem

2018 ◽  
Vol 33 (14n15) ◽  
pp. 1850088 ◽  
Author(s):  
J. L. Diaz-Cruz ◽  
W. G. Hollik ◽  
U. J. Saldana-Salazar
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Particle Physics ◽  
Weak Interactions ◽  
Theoretical Description ◽  
Strong Interactions ◽  
Top Down ◽  
Bottom Up ◽  
Elementary Particle Physics ◽  
The Standard Model

The strong CP problem is one of many puzzles in the theoretical description of elementary particle physics that still lacks an explanation. While top-down solutions to that problem usually comprise new symmetries or fields or both, we want to present a rather bottom-up perspective. The main problem seems to be how to achieve small CP violation in the strong interactions despite the large CP violation in weak interactions. In this paper, we show that with minimal assumptions on the structure of mass (Yukawa) matrices, they do not contribute to the strong CP problem and thus we can provide a pathway to a solution of the strong CP problem within the structures of the Standard Model and no extension at the electroweak scale is needed. However, to address the flavor puzzle, models based on minimal SU(3) flavor groups leading to the proposed flavor matrices are favored. Though we refrain from an explicit UV completion of the Standard Model, we provide a simple requirement for such models not to show a strong CP problem by construction.

scholarly journals The underlying geometry of the CAM gauge model of the Standard Model of particle physics

2020 ◽  
Vol 35 (07) ◽  
pp. 2050037
Author(s):  
Brian Jonathan Wolk
Keyword(s):  
Gauge Theory ◽  
Standard Model ◽  
Particle Physics ◽  
Clifford Algebras ◽  
Weak Interactions ◽  
Composition Algebra ◽  
Dirac Spinor ◽  
Yang Mills ◽  
Local Gauge Symmetry ◽  
The Standard Model

The Composition Algebra-based Methodology (CAM) [B. Wolk, Pap. Phys. 9, 090002 (2017); Phys. Scr. 94, 025301 (2019); Adv. Appl. Clifford Algebras 27, 3225 (2017); J. Appl. Math. Phys. 6, 1537 (2018); Phys. Scr. 94, 105301 (2019), Adv. Appl. Clifford Algebras 30, 4 (2020)], which provides a new model for generating the interactions of the Standard Model, is geometrically modeled for the electromagnetic and weak interactions on the parallelizable sphere operator fiber bundle [Formula: see text] consisting of base space, the tangent bundle [Formula: see text] of space–time [Formula: see text], projection operator [Formula: see text], the parallelizable spheres [Formula: see text] conceived as operator fibers [Formula: see text] attaching to and operating on [Formula: see text] [Formula: see text] as [Formula: see text] varies over [Formula: see text], and as structure group, the norm-preserving symmetry group [Formula: see text] for each of the division algebras which is simultaneously the isometry group of the associated unit sphere. The massless electroweak [Formula: see text] Lagrangian is shown to arise from [Formula: see text]’s generation of a local coupling operation on sections of Dirac spinor and Clifford algebra bundles over [Formula: see text]. Importantly, CAM is shown to be a new genre of gauge theory which subsumes Yang–Mills Standard Model gauge theory. Local gauge symmetry is shown to be at its core a geometric phenomenon inherent to CAM gauge theory. Lastly, the higher-dimensional, topological architecture which generates CAM from within a unified eleven [Formula: see text]-dimensional geometro-topological structure is introduced.

scholarly journals The Critical Relationship Between Quarks and Quantum Chromodynamics.

2021 ◽  
Author(s):  
Ayan Nayak
Keyword(s):  
Quantum Chromodynamics ◽  
Particle Physics ◽  
Weak Interactions ◽  
Strong Interactions ◽  
Abelian Gauge ◽  
Physical Systems ◽  
Fundamental Particles ◽  
The Standard Model ◽  
The Relationship ◽  
Crucial Part

The objective of this abstract is to perform a systematic review of the critical relationship between quarks and quantum chromodynamics. The topic of this review abstract is the relationship between quarks and quantum chromodynamics. This relationship has been considered and still is considered one of the most groundbreaking connections in particle physics as it has allowed scientists to get a better view at “quarks”, an elementary particle with no substructure. Quantum Chromodynamics expresses and is the theory of strong interaction between quarks and gluons which are fundamental particles making up hadrons such as neutrons and protons. The theory plays a crucial part in the standard model of particle physics. The quantum field theory supporting quantum chromodynamics is a non-abelian gauge theory in which the lagrangian will not undergo change under local transformations. Quarks are one half of the base on which quantum chromodynamics is founded on. Quarks play a crucial role in the functioning of quantum chromodynamics as a whole and as such, affect other physical systems closely related to quantum chromodynamics such as strong interactions, weak interactions, and spin classification. Fully understanding the relation between Quarks and Quantum Chromodynamics will allow us to understand the true roles that quarks play in complex quantum systems.

The Standard Theory

2017 ◽  
Author(s):  
John Iliopoulos
Keyword(s):  
Gauge Theory ◽  
Invariant Theory ◽  
Standard Theory ◽  
Strong Interactions ◽  
Gauge Invariant ◽  
Electromagnetic Interactions ◽  
Protons And Neutrons ◽  
Free Particles ◽  
Theoretical Predictions ◽  
Theory And Experiment

All ingredients of the previous chapters are combined in order to build a gauge invariant theory of the interactions among the elementary particles. We start with a unified model of the weak and the electromagnetic interactions. The gauge symmetry is spontaneously broken through the BEH mechanism and we identify the resulting BEH boson. Then we describe the theory known as quantum chromodynamics (QCD), a gauge theory of the strong interactions. We present the property of confinement which explains why the quarks and the gluons cannot be extracted out of the protons and neutrons to form free particles. The last section contains a comparison of the theoretical predictions based on this theory with the experimental results. The agreement between theory and experiment is spectacular.

scholarly journals A Brief Review of Implicit Regularization and Its Connection with the BPHZ Theorem

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 956
Author(s):  
Dafne Carolina Arias-Perdomo ◽  
Adriano Cherchiglia ◽  
Brigitte Hiller ◽  
Marcos Sampaio
Keyword(s):  
Field Theory ◽  
Quantum Field Theory ◽  
Gauge Symmetry ◽  
Particle Physics ◽  
Analytic Extension ◽  
Quantum Field ◽  
Loop Order ◽  
Time Dimension ◽  
The Core ◽  
Striking Success

Quantum Field Theory, as the keystone of particle physics, has offered great insights into deciphering the core of Nature. Despite its striking success, by adhering to local interactions, Quantum Field Theory suffers from the appearance of divergent quantities in intermediary steps of the calculation, which encompasses the need for some regularization/renormalization prescription. As an alternative to traditional methods, based on the analytic extension of space–time dimension, frameworks that stay in the physical dimension have emerged; Implicit Regularization is one among them. We briefly review the method, aiming to illustrate how Implicit Regularization complies with the BPHZ theorem, which implies that it respects unitarity and locality to arbitrary loop order. We also pedagogically discuss how the method complies with gauge symmetry using one- and two-loop examples in QED and QCD.

scholarly journals Structure of flavor changing Goldstone boson interactions

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Jin Sun ◽  
Yu Cheng ◽  
Xiao-Gang He
Keyword(s):  
Symmetry Breaking ◽  
Model Building ◽  
Neutral Current ◽  
Goldstone Boson ◽  
New Physics ◽  
Majorana Neutrino ◽  
Neutrino Masses ◽  
Type I ◽  
Flavor Changing ◽  
Flavor Changing Neutral Current

Abstract General flavor changing Goldstone boson (GB) interactions with fermions from a spontaneous global U(1)G symmetry breaking are discussed. This GB may be the Axion, solving the strong QCD CP problem, if there is a QCD anomaly for the assignments of quarks U(1)G charge. Or it may be the Majoron, producing seesaw Majorana neutrino masses by lepton number violation, if the symmetry breaking scale is much higher than the electroweak scale. It may also, in principle, play the roles of Axion and Majoron simultaneously as far as providing solution for the strong CP problem and generating a small Majorana neutrino masses are concerned. Great attentions have been focused on flavor conserving GB interactions. Recently flavor changing Axion and Majoron models have been studied in the hope to find new physics from rare decays in the intensity frontier. In this work, we will provide a systematic model building aspect study for flavor changing neutral current (FCNC) GB interactions in the fermion sectors, or separately in the quark, charged lepton and neutrino sectors and will identify in detail the sources of FCNC interactions in a class of beyond standard model with a spontaneous global U(1)G symmetry breaking. We also provide a general proof of the equivalence of using physical GB components and GB broken generators for calculating GB couplings to two gluons and two photons, and discuss some issues related to spontaneous CP violation models. Besides, we will also provide some details for obtaining FCNC GB interactions in several popular models, such as the Type-I, -II, -III seesaw and Left-Right symmetric models, and point out some special features in these models.

scholarly journals Multimessenger Probes for New Physics in Light of A. Sakharov’s Legacy in Cosmoparticle Physics

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 222
Author(s):  
Maxim Khlopov
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
New Physics ◽  
Physical Models ◽  
Beyond The Standard Model ◽  
Fundamental Relationship ◽  
Relationship Of ◽  
The Universe ◽  
Selection Of

A.D. Sakharov’s legacy in now standard model of the Universe is not reduced to baryosynthesis but extends to the foundation of cosmoparticle physics, which studies the fundamental relationship of cosmology and particle physics. Development of cosmoparticle physics involves cross-disciplinary physical, astrophysical and cosmological studies of physics Beyond the Standard model (BSM) of elementary particles. To probe physical models for inflation, baryosynthesis and dark matter cosmoparticle physics pays special attention to model dependent messengers of the corresponding models, making their tests possible. Positive evidence for such exotic phenomena as nuclear interacting dark atoms, primordial black holes or antimatter globular cluster in our galaxy would provide the selection of viable BSM models determination of their parameters.

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