All about bosons, the force carrying glue of the universe

Bosons are a class of elementary particles responsible for many of the forces and particles that make up the universe, including light, gluons, and the protons and electrons that make up the matter we see around us.

Some bosons are better understood than others, and while some have been observed, there could be more yet to be discovered. But all of them have one feature in common: they are force-carrying particles, and so they are responsible for mediating the fundamental forces in nature that stitch together all of the matter in the universe as well as mediating important nuclear reactions that give the universe life.

What are bosons exactly?

More specifically, bosons are elementary particles that have an integer spin value (0, 1, -1, 2, -2, etc.) which distinguishes them from fermions, which have a plus or minus half-integer spin value (1/2, -1/2, 3/2, -3/2, etc.). The plus or minus determines the direction of intrinsic angular momentum the particle will take.

The spin of a particle is a fundamental property that describes its intrinsic angular momentum. In the case of elementary particles, their spin can take on only certain specific integer or half-integer multiples of Planck's constant divided by 2π.

Bosons are known for their ability to occupy the same quantum state simultaneously, a phenomenon known as Bose-Einstein condensation. This means that two or more bosons can be in the same place at the same time, and they can have the same energy and momentum so that you can effectively treat all bosons sharing that state as one and the same. 

It’s this ability of bosons to share the same quantum state that is responsible for many of the forces and particles that make up the universe. It is thought to allow for the formation of phenomena such as superfluidity and superconductivity, which have important practical applications in fields such as materials science and electrical engineering. 

Who discovered bosons?

The concept of bosons was first introduced by the Indian physicist Satyendra Nath Bose in 1924 in a paper he wrote on the statistical behavior of photons. Bose's work laid the foundation for the development of Bose-Einstein statistics, which describes the statistical behavior of indistinguishable particles with integer spin.

Bose's work went largely unnoticed until 1925, when Albert Einstein, who was working on a similar problem, realized the significance of Bose's ideas and helped to popularize them. Together, Bose and Einstein developed the theory of Bose-Einstein statistics, which describes the behavior of bosons and their tendency to "clump together" in large numbers, forming a Bose-Einstein condensate at very low temperatures.

The name "boson" was later coined by the physicist Paul Dirac in honor of Bose's contributions to the field. Today, the study of bosons plays a crucial role in many areas of physics, including particle physics, quantum mechanics, and condensed matter physics, and has important practical applications in fields such as materials science and electronics.

What are the different kinds of Bosons?

There are four fundamental forces in the universe, and there are at least five bosons that we know of, with a possible sixth boson yet to be observed. There are different types of bosons. The types that we have evidence of include gauge bosons and scalar bosons. Gauge bosons (photons, W and Z particles, and gluons) act as force carriers for elementary fermions; a scalar boson is a boson whose spin equals zero (the Higgs boson is the only fundamental scalar boson in the Standard Model).

A sixth type of boson is the graviton, which is a gauge boson for gravity. It  has been theorized to exist, but no experimental evidence has yet been found for its existence.

Photon

A photon is a subatomic particle that is the fundamental unit of electromagnetic radiation, including light and is the force-carrying particle for the electromagnetic force. It has an integer spin of 1, and its spin is responsible for light's polarization property (e.g., the direction in which a light wave is orientated) at a macro level.

Photons have no mass, electric charge, or other inherent properties beyond their spin and energy. They travel at the speed of light in a vacuum and exhibit both wave- and particle-like properties. 

In addition to being the particle that makes up light, photons are also involved in a wide range of other phenomena, including the photoelectric effect, where photons are absorbed by materials and can release electrons, and in processes such as fluorescence, phosphorescence, and luminescence. 

Photons are also important in the field of quantum mechanics, where they are used in studies of quantum entanglement, teleportation, and quantum computing.

Z Boson

The Z boson is a carrier particle for the weak nuclear force, which is responsible for certain forms of radioactive decay and neutrino interactions.

The Z boson is quite massive compared to other elementary particles, with a mass of about 91 GeV/c². Notably, the Z boson is a neutrally charged particle, unlike its fellow weak nuclear force-carrying particle, the W boson. 

The Z boson was first observed in 1983 by the UA1 and UA2 experiments at CERN, through the study of proton-antiproton collisions in the Super Proton Synchrotron. 

W Boson

The W boson is also a force carrier for the weak nuclear force, along with the Z boson, but there are some key differences.

There are two types of W bosons, the W+ and the W-, which are each other's antiparticles. The W+ boson has a positive electric charge, while the W- boson has a negative electric charge. The W boson is also rather large compared to other elementary particles, like the Z boson, but a bit smaller than the Z boson, with a mass of about 80 GeV/c². 

The discovery of the Z and W bosons was a major milestone in particle physics, with the latter first observed in 1983 at CERN using the same Super Proton Synchrotron that found the Z boson. 

The discovery of the W boson, along with the earlier discovery of the Z boson, provided strong experimental evidence for the electroweak theory, which unifies the weak nuclear force and the electromagnetic force at very high energies.

The properties of the Z and W bosons have been studied extensively since their discovery, and their behavior has been found to be consistent with the predictions of the Standard Model. The Z and W bosons are also important in studies of the mechanism of electroweak symmetry breaking, which gives particles their masses.

Gluon

A gluon is the elementary force-carrying particle that acts as the exchange particle (or gauge boson) for the strong nuclear force between quarks. It is analogous to the exchange of photons in the electromagnetic force between two charged particles. Gluons bind quarks together, forming hadrons such as protons and neutrons.

Gluons are massless and have spin 1. They are also color-charged, which means they have a combination of two color charges (one of red, green, or blue and one of antired, antigreen, or antiblue) in a superposition of states. 

A gluon that has a color charge of red and antigreen can interact with a quark that has a color charge of blue. The gluon will transfer its color charge to the quark, changing the quark's color charge to red. This is how the strong force works.

The color charge of gluons is what gives the strong force its characteristic property of being confining. This means that quarks cannot be separated from each other, as they will always attract each other through the strong force. This is why protons and neutrons are so stable, as the quarks inside them are held together by the strong nuclear force.

Gluons are very difficult to study directly, as they only interact with each other and with quarks. However, their effects can be seen in the behavior of hadrons like protons, such as the way that they decay.

Higgs boson

The Higgs boson is a subatomic particle that was first theorized by physicist Peter Higgs, among others, in the 1960s. Dubbed the “God particle,” the Higgs boson is the particle that is responsible for conferring mass on other particles through their interaction with the Higgs field, which permeates the entire universe. 

The Higgs boson was later discovered in 2012 by scientists working at the Large Hadron Collider (LHC) at CERN. The discovery was an important moment for physics, as it confirmed the existence of the Higgs field and provided further evidence for the Standard Model. It also opened up new avenues for research and has the potential to lead to further discoveries about the nature of matter and the universe as a whole.

It is a force-carrying particle, but the force it mediates isn’t one of the four fundamental forces, despite mass’s previously held relationship to gravity under Newton’s classical mechanics. Instead, the Higgs boson mediates the force of the Higgs field with those particles that interact with it, even weakly, like the neutrino. Photons, for instance, are massless because they do not interact with the Higgs field, while the Z boson does.

Graviton

According to the theory of general relativity, gravity arises from the curvature of space-time caused by the presence of mass and energy. However, in the quantum theory of fields, all forces are thought to arise from the exchange of particles.

If the latter were true, then there must be something mediating the gravitational force, similar to how photons mediate the electromagnetic force. This particle has been given the name graviton, but no one has ever observed it despite decades of effort.

However, there is indirect evidence for their existence, such as the observed behavior of gravitational waves, which are ripples in space-time caused by the acceleration of massive objects.

If a graviton could be observed, it would have profound implications for our understanding of the universe, as it would provide a bridge between the theory of general relativity and the quantum theory of fields, which have been irreconcilable to the consternation of many physicists.