Fermions and Bosons

The fundamental objects of quantum field theory in physics are elementary particles. Elementary particles are the smallest particles with no other particle in their structure and immeasurable internal structures. That means their composition is unknown. They are the building blocks of the universe. All other matter is made up of these fundamental particles. The universe has two classes of elementary particles, Fermions and Bosons. Even composite particles such as neutrons fall under these two elementary particles. This article will discuss fermions characteristics and examples and bosons characteristics and examples. We will also learn the names for combinations of elementary particles.

Fermions: Characteristics 

Fermions are one of the two building blocks of matter. These particles were named after Enrico Fermi, a scientist.

Some characteristics of fermions are:

• They have mass.
• Fermion’s spin is always in multiples of half-integers such as ½, 3/2, 5/2, etc. 
• They follow the Pauli’s Exclusion Principle, which means that fermions are solitary. This means that only one fermion will occupy a particular space at a given time.  

Examples of Fermions

Fermion types are considered through two different methods- standard model and mathematics. The fermion types differ as per the method chosen. They are:

1). Standard Model– As per the standard model of particle physics, there are two types of fermions- quarks and leptons. 

• Quarks- These are the fundamental building blocks for all protons and neutrons. Quarks are of six types- up, down, charm, strange, top and bottom. Physicists also call the types of quarks “flavours”. 
• Leptons- These are also of six types- electron, electron neutrino, tauon, tauon neutrino, muon and muon neutrino. 

2). Mathematics-  As per mathematics, there are many types of fermions. The three most common examples of fermions as per mathematics are:

• Weyl Fermions or massless fermions.
• Dirac fermions or massive fermions.
• Majorana fermions.

Bosons: Characteristics 

Bosons are one of the fundamental particles of the universe. These subatomic particles were named after Satyendra Nath Bose, an Indian Physicist.

Some key characteristics of bosons are:

• They have integral spin numbers such as 1,  2, etc.
• They are made up of more than one particle.
• Bosons have nuclei with even mass numbers.
• They are made up of small bundles of light.
• Some bosons are force carriers. 

The Examples of Bosons

As per the standard model of particle physics, there are five types of elementary bosons broadly grouped into two categories. They are: 

1). Gauge Bosons- Gauge bosons are of four types- gluons, W and W-, Z bosons, and photons. All the gauge bosons have a spin number of 1 and carry three of the four fundamental forces. 

• Gluon- These bosons are massless and chargeless and strong force interaction carriers. 
• W and Z bosons- These are weak force-carrying particles. W bosons have two types: W, the matter particle and W – of the antimatter particle. The Z boson has its particular anti-particle. 
• Photon- These are massless and chargeless bosons that are electromagnetic force carriers. Some photons have a particular frequency that determines their electromagnetic radiation. Photons travel at a speed of 300,000km/s, which is the speed of light. 

2). Higgs Boson- These are the four-vector particles with a spin value of 1. These bosons have mass and are not just a complete bundle of energy. 

Composite Particles 

Composite particles are made from a combination of elementary particles in a bound state. Let’s learn about the names for combinations of elementary particles. 

1). Hadrons- These are strongly interacting combination particles. Hadrons are of two types:

• Composite Fermions- These are combinations of fermions. A composite fermion made of three quarks is called a baryon. 
• Composite Bosons- These are made of combinations of bosons. A composite boson made from two quarks is called a meson. 

2). Baryons – Ordinary baryons can either contain three valence quarks or three valence antiquarks. Baryons can be of different types. The names for combinations of elementary particles of baryons are:

• Nucleons- Composite particles with normal atomic nuclei constitution.

a). Protons: A combination of two up and one down quark.

b). Neutrons: A combination of one up and two down quarks. 

• Hyperons: They contain one or more strange quarks. These are short-lived and have more weight than nucleons. 
• Pentaquarks: They combine four valence quarks with one valence antiquark. 

3). Mesons- Mesons are composite bosons with a spin of 0 or 1 and are made up of a valence quark and antiquark. 

Conclusion: 

The characteristic that primarily differentiates bosons and fermions is their spin. Fermions are elementary particles with a half-integral spin, whereas bosons have an integral spin. Another difference is that Pauli’s exclusion principle is only applicable to fermions and not bosons. Learning about elementary particles and their characteristics is the first stepping stone to understanding the universe.