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An Insight Into Nature's Strongest Force


My name is Lloyd and I am in the third year of my PhD studying Theoretical Nuclear Physics. I am attempting to provide a better theory to describe the phenomenon of neutral pion (a relatively light, short-lived particle that is found in nuclear and particle reactions) production from a photon (light) incident on a proton (a nuclear particle that is found in the nucleus of every atom).  Before starting my research I studied theoretical physics at the University of Manchester.

Strong Nuclear forces remain to be one of the least understood processes in nature. Yet it is the source of immense energy that can power our cities, from harnessing the emitted radiation in power-plants; or level countries by concentrating radioactive materials in a bomb. The manner in which the fundamental matter particles (or quarks) exchange the strong force carrying particle (or the gluon boson) is far more complex than any of the other forces (weak nuclear, electromagnetic or gravity). Unlike the other forces, gluons themselves can carry a strong nuclear charge, known as colour charge; this allows them to interact with themselves in-between quark interactions, allowing for infinite scenarios to describe the simplest of processes. 

In Depth:

The study of the strong nuclear force is known as quantum chromodynamics (QCD), this theory helped scientists understand important properties of particle physics, mainly why we only see composite quark states in nature. In other words why you will never find a sole quark by itself, instead you will see it in bound states (hadrons) which form protons and neutrons (baryons) and lighter states such as pions (mesons). But trying to make any practical calculations with QCD is very difficult, so difficult in fact that if anyone were to solve the QCD equation into a usable form then they would win 1 million dollars from the Clay Mathematics Institute!

I do away with these complexities of QCD by only working in energy regimes where the protons and other hadrons won't break down into their constituent quarks. So we can describe proton or neutron scattering through pion exchange instead of using gluons. Furthermore, I take advantage of some symmetries present in QCD, related to the quark masses, to simplify aspects of the calculations. This is a very vague picture of the theory I work in called Chiral Perturbation Theory (ChPT).

My work has been motivated by a recent experiment in Germany at the Mainz Microtron by the A2 and CB-TAPS collaborations where they have obtained the most accurate data to date on this interaction. I am in the process of taking theories that have already been made to describe parts of this process and sticking them together to get a more complete picture of the reaction. The most important part I have included is an intermediate resonance state prior to pion emission.

This research isn't going to be part of the new fastest computer in 20 years time, nor is it going to cure diseases. But it will give us an insight in to what happens in nature at the sub-atomic level. Then maybe who knows what this might lead to in the future, 100 years from now it is impossible to predict how important this process will be in understanding nuclear fusion both in power plants or in stars. When Paul Dirac, one of the pioneers of quantum mechanics, predicted the existence of massless Dirac fermions in the 1920s he had no idea that a century later people would be trying to use these states within graphene to dramatically improve technology.

Going Further:

To follow exactly what it is I do I am afraid you will need a degree in theoretical physics, which you can start looking into at the University of Manchester. (

The European Centre for Nuclear Research (CERN) have lots of information available on particle and nuclear physics (

The Jefferson Lab in the USA also has useful information for students and teachers (

MAMI, the experimental group that analyse this interaction (