Color And Gluons

In Particle physics, particles are defined by various quantum numbers and are sorted out into groups as established in my first article. Today I will be discussing one of the most important concepts in the subject known as color defined by a study known as quantum chromodynamics (chromo-> color). Color charge in particular is property unique to quarks and is used to explain how they stay together to form hadrons. Color charge aren't standard charges such as + or - but rather their own type. Keep in mind that the color charge of a quark doesn't change the flavor of a quark and doesn't apply to free particles. This means that an up quark will stay an up quark even if it's color changes.  Also note that free particles and hadrons as a whole have no color charge in accordance to a theory known as color confinement. Physicists represent colorlessness with the color white.

Gluons are the massless mediators of color charges between quarks and a type of gauge boson (a set of force carrying particle) with the spin of 1. Gluons itself is both an anti-color and a color, this explains how gluons can change the color of other quarks. Take for example a green quark. If it were to turn into a red quark what would need to happen? Well a gluon with anti-green and red color would be needed. The green annihilates with the anti-green, just like anti-particles an normal particles would as established in my second article, and thus you are left with a red quark. Gluons also have the unique property of being able to split into pairs of gluon and/or do the same but with antimatter and matter particles. 

* not that in both these interactions the gluons change the color of both particles in the end.

The spring looking design on the Feynman diagram is a gluon (keep in mind the flat line above a symbol mean anti). Scientists theorize of a gluon field describes the motion of these gluons between quarks, including when they form anti-matter and matter pairs.

            

^flux tube

This field that causes the attraction between quarks is the result of flux tubes where gluons move from quark to quark. These are the field lines that attract quarks, just like normal charges have electric field lines that cause them to attract one another. This resulting force of attraction between quarks is known as the strong force.

  Because gluons have a color charge, they can attract one another by exchanging other gluons. This causes the flux tubes to bundle together between quarks. Essentially when gluons are emitted and absorbed between only two quarks, the field lines causing the attraction between the two quarks are linear rather than curved like that of its electromagnetic counterpart.

The image on the left is the strong force  while the right is electromagnetic force.

The image bellow is the picture of meson which interestingly contains two elementary particles one being of a certain color and the other being it's respective anti-color (red, anti-red). Remember  the only difference  is that mesons cannot have two differing color combinations like (green, anti-blue) because then the net color charge wouldn't be white, but gluons can do this. 

Keep in mind that the strength of the strong force between two quarks only operates at small distances because the strength of the strong force from the gluons is so high. As a result, if you put enough energy pulling the quarks apart, a pair of anti-matter and matter will form resulting in two or more mesons being produced. In the picture above, a meson splits into 2 new mesons after energy is applied to it.

Feynman Diagrams: Annihilation

Feynman diagrams define particle interactions with the use of two perpendicular axis. One that describes space where the particles interact and the other is time. Let's look at a basic diagram:

Here we see what scientists call annihilation. Essentially what this diagram says is that when a positron (electrons opposite) comes into contact with an electron it will for gamma radiation.

The question is why? well the answer comes from the basis of what particles are. Particles have no discrete boundaries and as such, we can treat them as standing waves that move in the same direction as the direction of the particle's motion itself (longitudinal waves). Electrons and positrons are standing waves with different phases so when they meet they "cancel" each other out meaning there are no more standing waves. But that doesn't exactly mean that there is no more waves entirely. According to energy conservation, that energy has to be released in some way, so these two subatomic particles release their energy by vibrating rapidly causing the production of a transversal waves or gamma rays. In this case its just two that are produced.

Its very important that you understand that these photons can also separate into electrons and positrons. You'll be surprised to know that interactions like this are happening everywhere around us even in space, and it's not just between these two particles, there are a variety of opposite pairs of particles that can be created. While the net amount of energy in this field cancels out. Some scientists even speculate that the expansion of the universe is the result of quantum fluctuations pushing cosmic bodies away from one another, expanding throughout space. It creates this really energetic bubbles of energy known as quantum foam. Its a huge reason why helium is unable to freeze even at absolute zero. General Relativity and Quantum mechanics don't exactly agree on what the energy of the field is with value ranging from infinite energy all the way to near zero, although close to zero is the more likely value. 

Introduction: Particles

Particle physics or high energy physics is the study of matter and radiation. I've tried my best to compile the study so far and provide a layman explanation to how it works.

First things we need to understand are flavors and particles. Particles are the building blocks of matter and radiation. These particles can also be used to explain interactions/behaviors of and between other particles. Flavor is a scientific term used to differentiate various particles in group.

When discussing particles such electrons, and gluons we must understand that each elementary particle has its own field containing fluctuations. Particles are nothing but excitations in this field; areas where the field is concentrated. ex. areas in the up quark field that are most concentrated are up quarks. This idea is known as Quantum Field Theory (QFT). When referring to excitations in a field, it's important to note these excitations have discrete energy levels or quanta. 

First we have fermions and bosons. Two identical fermion particles cannot have the same quantum state* while bosons are capable of doing this (Einstein-Bose Condensate). Fermions also have a half integer spin while bosons have integer spin numbers.

^Orange and Green particles are fermions,  blue and purple particles are bosons.

Bosons tend to be force carriers. They include vector bosons/gauge bosons (w/direction) and scalar (direction doesn't matter) bosons. The Higgs Boson is a good example of a scalar boson while the particles in blue are vector bosons.

Quarks and leptons are both types of fermions but are very different. Quarks unlike leptons interact with the strong force. This means that they emit and absorb gluons a type of gauge boson (force carriers) which in a sense glues quarks together. This way up and down quarks can make up protons and neutrons while electrons are incapable of doing so, and thus are not part of the nucleus of an atom.

 A hadron is is essentially a group of particles that stay together because of gluons.

 

Pictures show two types of hadrons consisting of fermions. The field that describes the motion of gluons in space between quarks is known as the gluon field, which we will discuss later.

Baryons are classified as fermions and are a subset of hadrons that contain particles in groups of an odd number of valence quarks and tend to be more stable. Mesons are classified as bosons and are another subset of hadrons which tend to decay quickly and consist of an equal number of quarks and antiquarks.

  * a system that is defined by quantum numbers which defines a particle itself,