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THE STANDARD MODEL OF ELEMENTARY PARTICLES

General

 

If we want to delve into the origin of matter, we have to descend to the smallest building blocks of matter : the elementary particles.  We find the overview of elementary particles in the Standard Model of particle physics.

The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetic, weak and strong interactions – excluding gravity) in the universe and classifying all known elementary particles. It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide [4], with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, proof of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to the Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy.

Although the Standard Model is believed to be theoretically self-consistent and has demonstrated some success in providing experimental predictions, it leaves some physical phenomena unexplained and so falls short of being a complete theory of fundamental interactions. For example, it does not fully explain baryon asymmetry, incorporate the full theory of gravitation[3] as described by general relativity, or account for the universe's accelerating expansion as possibly described by dark energy. The model does not contain any viable dark matter particle that possesses all of the required properties deduced from observational cosmology. It also does not incorporate neutrino oscillations and their non-zero masses.

The development of the Standard Model was driven by theoretical and experimental particle physicists alike. The Standard Model is a paradigm of a quantum field theory for theorists, exhibiting a wide range of phenomena, including spontaneous symmetry breaking, anomalies, and non-perturbative behavior. It is used as a basis for building more exotic models that incorporate hypothetical particles, extra dimensions, and elaborate symmetries (such as supersymmetry) to explain experimental results at variance with the Standard Model, such as the existence of dark matter and neutrino oscillations.

The deconstruction of the Standard Model [6]

The Standard Model of particle physics is often visualized as a table (Figure 1), similar to the periodic table of elements, and used to describe particle properties, such as mass, charge and spin. The table is also organized to represent how these teeny, tiny bits of matter interact with the fundamental forces of nature.

But it didn’t begin as a table. The grand theory of almost everything actually represents a collection of several mathematical models that proved to be timeless interpretations of the laws of physics.

This version of the Standard Model is written in the Lagrangian form. The Lagrangian is a fancy way of writing an equation to determine the state of a changing system and explain the maximum possible energy the system can maintain (Figure 2).

Section 1

These three lines in the Standard Model are ultraspecific to the gluon, the boson that carries the strong force. Gluons come in eight types, interact among themselves and have what’s called a color charge.

Section 2

Almost half of this equation is dedicated to explaining interactions between bosons, particularly W and Z bosons. Bosons are force-carrying particles, and there are four species of bosons that interact with other particles using three fundamental forces. Photons carry electromagnetism, gluons carry the strong force and W and Z bosons carry the weak force. The most recently discovered boson, the Higgs boson, is a bit different; its interactions appear in the next part of the equation.

Section 3

This part of the equation describes how elementary matter particles interact with the weak force. According to this formulation, matter particles come in three generations, each with different masses. The weak force helps massive matter particles decay into less massive matter particles. This section also includes basic interactions with the Higgs field, from which some elementary particles receive their mass. Intriguingly, this part of the equation makes an assumption that contradicts discoveries made by physicists in recent years. It incorrectly assumes that particles called neutrinos have no mass. 

Section 4

In quantum mechanics, there is no single path or trajectory a particle can take, which means that sometimes redundancies appear in this type of mathematical formulation. To clean up these redundancies, theorists use virtual particles they call ghosts. This part of the equation describes how matter particles interact with Higgs ghosts, virtual artifacts from the Higgs field. 

Section 5

This last part of the equation includes more ghosts. These ones are called Faddeev-Popov ghosts, and they cancel out redundancies that occur in interactions through the weak force.

 

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Figure 2 - The deconsteructed Standard Model Equition

Literature [1] 

  • Stephen Blaha  (2010) Relativistic Quantum Metaphysics: A First Principles Basis for the Standard Model of Elementary Particles.  Pingree-Hill Publishing

  • Andrzej Derdzinski  (2013) Geometry of the Standard Model of Elementary Particles.  Springer  [OLN B102]

  • Gordon Kane  (2017) Modern Elementary Particle Physics - Explanation and Extending the Standard Model.  Cambridge University Press  [OLN B051]

  • D. Kazakov, S. Lavignac, J. Dalibard  (2003) Particle Physics beyond the Standard Model.  Elsevier Science

  • Paul Langacker  (2017) The Standard Model and Beyond.  CRC Press  [OLN B003]

  • D. B. Lichtenberg  () The Standard Model of Elementary Particles.  Amer Inst of Physics

  • Richard Lighthouse  (2015) New Standard Model for Elementary Particles.  Kindle

  • Yorikiyo Nagashima  (2014) Beyond the Standard Model of Elementary Particle Physics.  Wiley  [OLN B107]

  • Yorikiyo Nagashima  (2013) Elementary Particles Vol 2 - Foundations of the Standard Model.  Wiley

  • Robert Oerter  (2006) The Theory of Almost Everything.  Penguin Publishing Group  [OLN B104]

  • C. Quigg  (1997) Gauge Theories of the Strong, Weak and Electromagnetic Interactions.  Addison-Wesley  [OLN B074]

  • Florian Scheck  (2002) Noncommutative Geometry and the Standard Model of Elementary Particle Physics.  Springer

  • Wouter Schmitz  (2022) Particles, Fields and Forces :  A conceptual guide to Quantum Field Theory and the Standard Model.  Springer  [OLN B105]

  • Matthew D. Schwartz  (2014) Quantum Field Theory and the Standard Model.  Cambridge University Press  [OLN B053]

References

[1]  For the titles marked with an Online Library Number (ONL), you can access the ebook directly

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