Computing Resources and Software Support for the UKQCD Physics Programme

QCD is the quantum theory of the strong interaction, formulated in terms of elementary entities called quarks and gluons. In a laboratory, however, we only observe composite objects such as protons (qqq) or pi-mesons ( q -- anti-q), collectively known as hadrons. Explaining this dichotomy in a satisfactory way is a major unresolved question in theoretical physics, and indeed commands a prize of 1 million dollars from the Clay Mathematics Institute. In the interim, many important QCD questions can be addressed using a controlled approximation called lattice gauge theory, in which quarks and gluons are formulated only on the discrete points and links of a spacetime lattice. Properties such as the masses and interactions of hadrons, and the nature of the gluonic flux tube which holds quarks together with a force sufficient to lift 3 elephants can then be calculated using a numerical technique called Monte Carlo Importance Sampling. Precise lattice QCD results are now a crucial ingredient in projects which, by comparing theoretical predictions with the results of collider experiments, aim both to determine parameters of the Standard Model of particle physics, and if inconsistencies are found, to open up the exciting prospect of 'new physics'. Unfortunately, the number of lattice points required to make the calculations with the necessary precision is large, as is the computational effort associated with intermediate steps of the calculation once the quarks are assigned realistically small masses. In this proposal we argue that in order to achieve the required accuracy state-of-the-art high performance computing resources are needed; indeed, we cost our bid in units of 'teraflop-years', equivalent to some 3x10^19 individual computer operations. Lattice QCD is truly a Grand Challenge. The projects presented in this bid cover a broad sweep of different physics, ranging from precision calculations of hadrons; the properties of systems including heavy quarks such as 'charm' and 'bottom'; extracting fundamental parameters of the Standard Model of Particle Physics (such as the masses and decay properties of hadrons); the quark-gluon plasma which forms at temperatures in excess of a trillion kelvin; the exotic 'quark matter' thought to exist in the cores of neutron stars (having the mass of the Sun but compact enough to comfortably fit in Swansea Bay!); finally, the properties of QCD-like models in which the numbers of quarks and gluons differs from their real- world values of 3 and 8, offering the tantalising promise of making contact with pencil-and-paper approaches and ultimately the Clay prize....