Particles. They make up everything around us and are something we most definitely come into contact with at all times, our very bodies being constructed from these ridiculously small bits of matter. Many of you will be familiar with the likes of neutrons, protons and electrons (I hope, anyway), the main particles that make up atoms. However, science is never that straightforward (Which is unfortunate, sometimes. Waves still allude me…).
Scratch just a little bit below the surface and you’ll encounter the Particle Zoo, a culmination of decades of research dating back as far as 1897 with the discovery of electrons by one J.J Thomson (1). Together, we shall explore the weird and wonderful world of particles and I figured the best place to start would be with their classification.
The Standard Model
The Standard Model contains particles that are referred to as elementary or fundamental. The particles include those responsible for 3 of the 4 fundamental forces as well as matter particles, particles that make up other particles. The Standard Model has been used to successfully predict a number of phenomena observed which has resulted in it becoming a well-tested physics theory (2).
Hadrons are particles that can be broken down into smaller particles known as quarks. This property means that we refer to them as non-fundamental. They do not feature on the Standard Model as result of their composite nature (Being made of even smaller particles) Hadrons are known for being influenced by the strong nuclear force both inside themselves and with other hadrons (3). There are two types of hadrons: baryons and mesons.
Baryons – Baryons are particles that are made up of either 3 quarks or 3 anti-quarks. These include particles like the proton and neutron one finds in the nucleus of an atom.
Mesons – Mesons differ from Hadrons in their quark composition. Mesons contain one quark and one anti-quark. Examples of mesons include Pions and Kaons.
Leptons are fundamental particles, particles that cannot be broken down any further (as far as we know). Each Lepton has its own neutrino, a particle with almost no mass and zero charge. Unlike Hadrons, Leptons don’t experience the strong nuclear force but they all experience the weak nuclear force instead. Leptons include particles such as the electron, the muon and tau.
Also known as force carriers, bosons or exchange particles are responsible for the fundamental forces experienced by matter. However, they currently only cover 3 of the fundamental forces, gravity thus far alluding the science community (Though a particle, the graviton, has been theorised to be responsible for gravity).
We’ll look at that this in more detail later but every known particle also has an anti-particle equivalent. They possess the same mass are their particle equivalent but charged antiparticles have a charge that is opposite to their particle equal. When a particle and anti-particle interact, annihilation occurs which involves the particles converting their combined mass into energy.
As may have become clear from this rather brief exploration of the world of particle physics, there are an awful lot of particles out there, many of which have yet to be experimentally discovered. With Particle Zoo I intend for us to explore this strange world, covering everything from nucleons to string theory (The latter being something I know nothing about but am excited to wrap my head around). If you have any thoughts or questions please feel free to leave them in the comments. Thank you.
- BBC Bitesize (2017) Development of Atomic Theory [online] Last Accessed 19 September 2017: http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/periodic_table/atomstrucrev5.shtml
- CERN (2017) The Standard Model [online] Last Accessed 19 September 2017: https://home.cern/about/physics/standard-model
- O’Neill M. (2016) OCR A-Level Physics A Student Book 2, Pearson Educated Limited, London
- Rincon P. (2012) Higgs-boson like particle discovery claimed at LHC [online] Last Accessed 20 September 2017: http://www.bbc.co.uk/news/world-18702455