Lattice QCD
Quantum Chromodynamics (QCD) describes the interactions of quarks and gluons via the force of Nature called the strong force. It is the force responsible for the properties, e.g., masses, of their bound states (called hadrons). The calculation of hadron masses, however, can only be done by the numerical simulation of QCD on a lattice of space-time points. It is designated internationally as a "Grand Challenge" project, requring powerful supercomputers. We use STFC's DiRAC High Performance Computing facility, in particular the powerful machine known as Darwin at the Cambridge High Performance Computing Service.
Research at Glasgow
Glasgow is part of the international HPQCD collaboration which includes teams from the UK (Glasgow, Cambridge and Plymouth), the USA, Canada and Spain. We have been leading progress worldwide in accurate calculations of hadron masses, their weak and electromagnetic decay rates, and hadronic form factors related to transitions from one 'flavour' of quark to another. To do this we have developed a particularly effective way of handling quarks on a space-time lattice called the Highly Improved Staggered Quark (HISQ) formalism. This enables us to efficiently include in our calculations the effect of energy fluctuations that create gluons and quark-antiquark pairs (sea quarks) allowing a fully realistic picture of the background strongly-interacting 'soup' in which the valence quarks that make up the hadron live. When applied to heavy quark flavours (charm and bottom), an approach developed at Glasgow and referred to as the 'heavy HISQ' method, this permits a fully relativistic treatment of heavy mesons, without need to rely on an effective theory treatment for the heavy quark. Matching the effective theory (e.g. NRQCD or heavy quark effective theory) to the Standard Model had been a limiting source of uncertainty.
One area in which we are focused is the calculation of hadronic form factors to permit the Standard Model prediciton of flavour-changing transitions. The goal of studying these transitions is to probe the Standard Model description of the weak force. The dominant source of uncertainty in this study is that coming from the hadronic interactions, placing lattice QCD on the frontline of this effort. Our heavy HISQ calculations are signficantly reducing this uncertainty, permitting greater scrutiny of the weak sector of the Standard Model.
In addition to heavy flavour physics, we are also working on nucleon physics and muon g-2. You can see our recent published works on INSPIRE. If you want to know more about related research opportunities, please get in touch with Dr. Bouchard or Dr. Harrison.