Annihilation Reactions

Series 1

Blog Post 1: An Introduction.

The first set of discoveries of an atom, the building blocks of all matter, was made by physicists J.J. Thompson, Ernest Rutherford, Neils Bohr as well as James Chadwick. These brilliant minds are well known for their discoveries and theories of the surface level sub-atomic particles – protons, neutrons and electrons.

However, as time passed, we have learnt that there is more than what meets the eye. Protons and neutrons are made of quarks, which come in different ‘flavours’ (yes, that is what they call them) and other subatomic particles such as neutrino, photons, muons, gluons, pions, mesons, leptons, hadrons, bosons and the list goes on. These subatomic particles have more versions of themselves as well! Gosh, my head is already spinning! We will get into each one of these crazy particles later!

Each of these particles have their own anti-particle as well, which is nothing but a particle with same mass but opposite electrical/magnetic charge. For example, an electron’s antiparticle is a positron, or a neutrino’s antiparticle is an anti-neutrino. Each of these particles and antiparticles all have the same mass, but an equal yet opposite charge.

This is where the whole aspect of an annihilation reaction comes into play. Annihilation as a word means complete destruction. So, an annihilation reaction is basically when a subatomic particle collides with it’s anti-particle to produce two respective particles, and the product depends on the initial particle set, the energy of collision and many other factors. Remember that the momentum and energy with which the initial particle and anti-particle collide is conserved, so the products have the same values of energy and momentum. This law must be obeyed!

Let us take an electron and it’s anti-particle, a positron. When these two particles undergo an annihilation reaction at low-energy levels, two photons are produced. However when positron and electron collide at high energy levels, they produce charm quarks (this is one of the four ‘flavours’ of quarks), which give rise to mesons (a particle made of a quark and it’s antiquark). Now you may ask me why mesons don’t annihilate. Well, that is slightly complicated, so I will explain that later on in this particular series.

So, that’s is a mere surface skim of the basics of annihilation reactions and the various subatomic particles, that I bet you never even knew existed until know! Feel free to drop by an email and ask me any questions! Keep being curious, and stay tuned to my follow-ups as we get deeper and deeper into the world of particle physics!

Have a great day ahead!