Fundamental Particle Physics

The research of the Fundamental Particle Physics group centres on theoretical studies of the elementary particles of nature such as the structure of protons and neutrons as well as developing testable theories for the physics which lies beyond the Standard Model of particle physics. The group members are Profs Gracey, Hands, Jack, Jones, Teubner and Vogt, Drs Buividovich, Fischer, Gorbahn, Rakow and Schaich.

The central tool for these theoretical investigations is quantum field theory and the group has world leading experts in perturbation theory and lattice gauge theory. In perturbative computations analytical and numerical methods are used to evaluate the higher order Feynman diagrams underpinning the different physical processes which take place in high energy particle colliders such as the Large Hadron Collider (LHC) at CERN in Geneva, at storage rings such as the (g-2) experiment at FNAL near Chicago or at so-called meson factories. By contrast lattice gauge theory uses supercomputers to study the physics of the quarks and gluons which compose hadrons such as protons and neutrons. The actual mechanism which achieves this is the strong force which is described by the quantum field theory called Quantum Chromodynamics (QCD).

Currently Particle Physics is entering an exciting phase of exploration of the Standard Model and physics Beyond the Standard Model (BSM) as a result of the latest data from many experiments such as the LHC, neutrino experiments, searches for dark matter as well as low energy hadron and lepton experiments. The Fundamental Particle Physics group is contributing to these debates and developments. For instance, one topic of major interest which Teubner is involved with is the measurement of the anomalous magnetic moment of the muon, called (g-2), which currently shows a tantalising 3-4 sigma discrepancy between the Standard Model prediction and its experimental measurement. This is possibly a sign of New Physics. A parallel activity is carried out by Gorbahn who analyses rare decays of b-quarks as they are also sensitive to BSM physics.

It is a major theoretical exercise to predict the underlying Quantum Mechanical effects through higher order corrections to assist with the interpretation of experimental data. As the strong interaction is the main source of this, work in the group is focused on pushing perturbative calculations in QCD to the limit of analytical computability. Current precision means that fourth order computations are achievable and Liverpool is a main centre for this goal.< /p>

Rakow, whose expertise is lattice gauge theory, use supercomputers to understand hadron properties from first principles. In particular, we are investigating flavour symmetry breaking effects coming from the differences in masses between the different types of quark, the corrections to pure QCD coming from the electromagnetic interaction and making predictions for electromagnetic form factor measurements for experiments such as those taking place at Jefferson Lab.

Schaich's lattice gauge theory research focuses primarily on BSM physics. Efforts in three related areas are currently supported by a UK Research and Innovation Future Leader Fellowship.  The first of these addresses the possibility that the Higgs boson and the dark matter of the Universe may be composite particles produced by some as-yet unknown strongly interacting quantum field theory.  The second area uses numerical lattice calculations to analyse supersymmetric quantum field theories and test the 'holographic duality' conjecture that relates these systems to the quantum dynamics of space-time itself.  Finally, we are also working with the emerging technology of quantum computing to develop and test new approaches to simulation that may far surpass traditional algorithms.

Buividovich uses lattice discretization of space-time to study the transport properties of strongly interacting quantum fermions, such as quarks in the quark-gluon plasma and electrons in crystalline solids such as graphene. He is particularly interested in transport phenomena which originate in quantum anomalies, violations of classical symmetries by quantum systems. He is also studying the emergence of quantum entanglement and quantum chaos in quantum fields.

Hands works in lattice field theory, with particular interest in systems at non-zero temperature and particle density, which help describe the diverse environments found on the one hand in experimental collisions between relativistic nuclei, and on the other at the cores of neutron stars. He also studies  "Flatland" theories of fermions in 2+1 dimensions, which as well as being interesting from the fundamental perspective of strongly-interacting quantum field theory also have many applications to layered systems in condensed matter physics. He has recently started working with models capable of quantum simulation using arrays of cold atoms trapped on optical lattices. He is a member of the FASTSUM collaboration studying hot QCD using an anisotropic lattice, and also Community Development Director of the DiRAC High Performance Computing Facility.

The Liverpool group is also home to experts in the use of Renormalization Theory to study novel ideas in quantum field theory which has applications not only in particle physics, but also in conformal field theory and related condensed matter problems as well as in quantum gravity, where the goal is to construct a scale invariant `Theory of Everything'.