Particle Physics

My PhD research was at the Theory Group of Manchester University Physics Department where I was interested in light mesons. These are bound states of quarks, the building blocks of the strong nuclear interaction. The mesons can be represented in an effective mesonic Lagrangian, which encodes constraints on meson properties that are imposed by the fundamental interaction symmetries. For example, it turns out that chiral symmetry imposes a very small rate for the meson decay of a rho meson into four pions, a theoretical prediction that has now been confirmed by experiment. An alternative approach is to use a scheme that represents the mesons explicitly as quark composites, such as the famous NJL model. I studied and developed a nonlocal generalization of this model, which resolves several of its traditional theoretical problems, but still retains much of the simplicity that is the chief merit of the model. One of the issues with a NJL-type scheme is that calculations are usually performed at leading order in the expansion parameter one-over-Nc. In fact, the number of colours, Nc=3, so convergence is slow. However, a nonlocal form is particularly well suited to performing calculations at next-to-leading order. Results suggest that several aspects of the usual leading-order approach work really rather well.

Some links for this work:

Papers:

1. My paper on the rho meson to four pion decay. (Preprint version.)
2. A paper on the representation of mesons in a nonlocal NJL model. (Preprint version.)
3. A paper on a nonlocal NJL model at next-to-leading order. (Preprint version.)

Thesis:

1. My PhD thesis.

Talks:

1. A talk on the pi0-gamma-gamma* form factor presented at the Particle Physics and the Early Universe conference in Cambridge.
2. A talk on the non-local NJL model presented to the Theory Group at Manchester.

Posters:

1. A poster I produced at the end of my second year. (Aimed at incoming PhD students.)

Background:

1. A review of chiral symmetry.
2. A review of how spin-1 states can be incorporated into effective Lagrangians.
3. A review (one of many) of the NJL model.
4. The experimental measurement of the rho meson to four pion decay.