Lattice QCD and the Standard Model of Particle Physics

Lead Research Organisation: University of Cambridge
Department Name: Applied Maths and Theoretical Physics

Abstract

We shall carry out calculations using Quantum ChromoDynamics to study the forces
that bind quarks into observable particles known as hadrons.

The key aim of this project is to improve our understanding of the Standard
Model including Quantum Chromodynamics (QCD) which describes how quarks are held
together inside nuclei. Quarks are never seen as free particles, so that
experimental information can only be obtained from the study of bound states of
quarks, known as hadrons. The aim is to solve QCD in the context of the
Standard model more accurately, so we can connect the fundamental properties of
quarks to the experimental information gained from hadrons, notably from the
Large Hadron Collider at CERN. Numerical methods known as lattice QCD are a
precision tool in this endeavour.

The Standard Model of particle physics unifies three forces of nature: the weak,
electromagnetic and strong forces. Except for gravity the Standard Model is
extraordinarily successful in accurately predicting the outcome of experiments
and includes the theory of electromagnetism, atomic physics, the forces that
bind nucleons in the nucleus and radioactive decay. At the LHC the Standard
Model is being tested to extreme levels and, in particular, in high energy
processes where any inadequacy of the model is most likely to be detected. This
centres partly on the existence or not of the Higgs particle but if there is any
physics "beyond the Standard Model" (BSM) a signal will be found in the
disagreement between experimental measurements of particular processes and
theoretical prediction based on the Standard Model alone. Any discrepancy is
likely to be small but must ultimately be resolved by new BSM physics. It is
crucial, therefore, to develop calculational techniques that can reliably and
accurately compute predictions for these processes.

We will use the new DiRAC phase-2 supercomputer and especially the Tightly
Coupled Cluster (TCC) part in the HPCs in Cambridge to carry out intensive
calculations using lattice QCD. In particular, some properties of particles
containing at least one heavy quark (in practice the b or c quark) are very
sensitive to the fine details of the Standard Model, and we have developed
special techniques for studying these properties on a space-time lattice. We are
part of the UKQCD national consortium and also of the HPQCD international
collaboration (www.physics.gla.ac.uk/HPQCD) and will use lattice techniques
which allow us to carry out ab-initio calculations with good control over
systematic and statistical errors enabling us in some cases to predict
observable quantities to within 1% total error.

For example, the properties of interest that are a stringent test of the
Standard Model are the decays of B mesons which are mesons containing one b
quark and one light, u or d, quark, and of Bs where the u or d quark is replaced
by a strange quark. These decays will be measured in the LHCb experiment at the
CERN LHC.

Our work brings together research done by many theorists and experimentalists to
carefully probe physics at high energies and to search for BSM physics.

Planned Impact

Pathways to Impact are as agreed at a meeting on 21st November 2011

Publications

10 25 50
 
Description This grant is for capital funding of the part of the STFC DiRAC Facility hosted at the HPCs in the University of Cambridge. It serves the whole UK STFC research community for computing in particle physics, astronomy, astrophysics and cosmology. The publications are a selection form the HPQCD particle physics group. There are many more to which I do not have access as this is a service grant designed to deliver the capital resource to the DiRAC@HPCs through the PI.
Exploitation Route No findings as such since this grant is for capital to buy and install the DiRAC@HPCs computer proving computing resources to STFC researchers.
Sectors Education

Other

 
Description To provide capital grant for purchase of the node of the STFC DiRAC Facility hosted at the HPCs in Cambridge to provide computing resources for UK STFC researchers.
First Year Of Impact 2012
Sector Education,Other
 
Description UKQCD/HPQCD 
Organisation University of Glasgow
Department Physics and Astronomy Department
Country United Kingdom 
Sector Academic/University 
PI Contribution Perturbative improvement of effective actions using automated proceedures.
Collaborator Contribution joint research over many years. We have studied perturbative improvement of effective actions used by Prof Davies at Glasgow and her group has collaborated on analysids to get final outcome.
Impact various publications under the HPQCD banner, workshops and group meetings.