Research
Lattice QCD
Quantum chromodynamics (QCD) is the theory of the strong force and describes the interactions between quarks and gluons. If the energy is high enough, one can calculate properties of the theory using perturbative QCD. Lattice QCD is a non-perturbative approach to solving this theory and it becomes absolutely essential when the energy is too low for perturbative QCD to be useful.
NRQCD
I'm currently working on lattice non-relativistic quantum chromodynamics (NRQCD). It is an effective theory which is useful for studying quarks that are heavy, like the bottom quark.
Bottomonium
I am looking at the Υ and ηb mesons (both bottomonium mesons - a bottom quark and its antiparticle bound together) and their behaviour at different momenta. The results of the lattice calculations can then be matched to continuum QCD allowing for very precise measurements of properties of these particles that can be compared to experiment
Using NRQCD we have recently calculated various experimentally measurable things: the leptonic width of the Υ and Υ', which is the rate at which the Υ and its first excited state decay to a pair of electrons; the mass of the bottom quark; and the contribution a b quark loop makes to the hadronic part of the anomalous magnetic moment of the muon.
Semileptonic Decays
In semileptonic decays, one of the constituent quarks of a meson emits a W boson (gauge bosons are the particles that mediate the force between the other particles). In the process, it changes flavour (this just means it changes from one type of quark to another), and the W boson subsequently decays into a lepton - like an electron - and a neutrino. A schematic representation of this decay is show below. In lattice QCD, we can't calculate anything related to what happens to the W boson after it is emitted, but we can calculate the properties of the initial and final state mesons and the effect that emitting a W boson has on them. In that way we can compare lattice calculations to experiment and extract useful results.
In particular I am interested in decays of the sort, B → πlν because one of the quarks in the meson is a bottom quark, so NRQCD can be used, while the other is a lighter quark, an up or a down quark. Similarly, the Bs particle, comprising a bottom quark and a strange quark or the Bccomprising a bottom quark and charm quark, can be simulated with NRQCD b quarks.