Yet, the Standard Model isn't complete. It lacks several key components necessary to fully comprehend our universe -- the hypothetical particles that make up dark matter, the particles responsible for gravity, and an explanation for the mass of neutrinos. Without these, our understanding of the universe remains a puzzle with missing pieces.
The Standard Model, as it stands, provides us with an inconsistent perspective of the natural world. Attempts to refine it so far have been oversimplified, perplexing, or inadequate.
The popular depiction of a particle periodic table, while helpful, fails to shed light on the relationships among the particles. It places the force-carrying particles (the photon, the W and Z bosons, and the gluons) on the same level as the matter particles they influence, while also neglecting key properties such as 'color'.
A different visual interpretation was created for the 2013 movie Particle Fever, placing undue emphasis on the Higgs boson – a critical component of the Standard Model. However, this representation inaccurately positions the Higgs particle alongside the photon and gluon, and the circle's quadrants are misleading.
Chris Quigg, a particle physicist at the Fermi National Accelerator Laboratory in Illinois, has spent decades brainstorming a more accurate visualization of the Standard Model. His goal is to help people understand known particles and encourage them to consider how these particles can be organized for better comprehension.
Quigg's representation unveils a deeper order and structure than the Standard Model. He refers to his model as a 'double simplex', with right-handed and left-handed particles each forming a simplex, an extension of a triangle. Quigg's model has since been further modified.
Constructing the double simplex
Matter is composed of two varieties of particles, leptons and quarks. However, we know that there exists for each particle its antiparticle of "antimatter" with equal mass but opposite charge and spin. However, we will not deal with these particles, which would form an inverted double simplex.
The quarks we are interested in are essentially of two types and form protons and neutrons by arranging themselves in triplets within the atomic nucleus. These quarks are the top quark of 2/3 charge and the down quark of - 2/3 charge. The up and down quarks can be "left-handed" or "right-handed" depending on whether rotation or "spin" occurs clockwise or counterclockwise with respect to their direction of motion.
"Left-handed" up and down quarks can turn into each other through an interaction called the weak force. This happens when quarks exchange a particle called a W boson-one of the weak force-carrying bosons with an electric charge of +1 or -1. In nature there are no right-handed W bosons. This means that right-handed up and down quarks cannot emit or absorb W bosons, so they do not turn into each other.
Quarks also possess a charge called "color." A quark can have a red, green or blue charge. The color of a quark makes it sensitive to the strong force. The strong force binds together quarks of different colors into protons and neutrons, which are "colorless," that is, they have no net color charge.
Quarks change color by absorbing or emitting particles called gluons, which are the carriers of the strong force. Since gluons themselves possess a color charge, they constantly interact with each other as well as with quarks.
In contrast, leptons are of two types: electrons, which have an electric charge of -1, and neutrinos, which are electrically neutral. In the same way as left-handed up and down quarks, electrons and left-handed neutrinos can transform into each other through weak interaction. Right-handed neutrinos, on the other hand, have not been observed in nature. Note that leptons do not possess color charge and do not "feel" the strong force; this is the main characteristic that distinguishes them from quarks.
The structure of the simplex
Now imagine looking at a diagram with the "left-handed" particles on the left and the right-handed ones on the right; they form the basic skeleton of Quigg's double simplex.
Now for some reason unknown to us, there are in nature three progressively heavier but otherwise identical versions of each type of matter particle.
For example, along with the up and down quark, there are the charm and strange quarks, and even heavier, the top and bottom quarks. The same goes for leptons: along with the electron neutrino, there are the muon neutrino and the tau neutrino (note that neutrinos have small but still unknown masses).
All these particles are found at the corners of the double simplex. It can be seen that a small amount of weak interaction occurs between left-handed quarks in different generations, so that an up quark could occasionally emit a W + boson and become a strange quark. Leptons of different generations also occasionally interact in this way.
Particle Interactions and Forces
How do particles communicate with each other? The majority of particles, with the exception of neutrinos, possess an electric charge. This characteristic makes them responsive to the electromagnetic force. Their interaction is facilitated by the exchange of photons, the fundamental carriers of the electromagnetic force. Noteworthy, these interactions do not result in transformation of particles into one another, rather they instigate attraction or repulsion.
Next, we delve into the intricate nature of the weak force. Besides the W+ and W- bosons, which are the charged carriers of the weak force, there exists a neutral carrier of the weak force, known as the Z0 boson. Particles can absorb or emit Z0 bosons without altering their identity. These "weak neutral interactions" simply result in the loss or gain of energy and momentum.
The similarity between weak neutral interactions and electromagnetic interactions is no coincidence. They were once unified as a force called the electroweak interaction, which existed during the earliest moments of the universe.
As the universe underwent rapid expansion and cooling, a phenomenon known as "symmetry breaking" separated these two forces into weak and electromagnetic. This division was signalled by the emergence of the Higgs field, which pervades the entire universe. The discovery of the Higgs boson, closely associated with the Higgs field, was a significant breakthrough at CERN in Geneva.
The Arrival of the Higgs Boson
The Higgs boson, the linchpin of the standard model, brings clarity to the double simplex arrangement. When the Higgs field infiltrated the primordial universe, it amalgamated left-handed and right-handed particles, which interacted with the field and gained mass. Here, it's important to note the mysterious origin of neutrino's mass, as it arises from a different mechanism than the Higgs.
How does a particle gain mass? When a particle like an electron traverses through space, it continually interacts with Higgs bosons, which are excitations of the Higgs field. On colliding with a Higgs boson, the electron can deflect in a new direction and switch from left-handed to right-handed, and vice versa. These interactions decelerate the electron, giving it "mass."
In essence, the more a particle interacts with excitations of the Higgs field, the more mass it gains. Furthermore, frequent interactions with Higgs bosons result in massive particles being quantum mixtures of right and left-handers.
This brings us to the visualization of the Standard Model of particles. Understanding the interactions and forces within this model provides a deeper insight into the fundamental structure of the universe.
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