Lattice QCD reveals infrared behaviour of gluon and ghost interactions.

Analyses of four-gluon and ghost-gluon interactions within the Landau gauge utilising lattice quantum chromodynamics have refined the understanding of infrared behaviour. Improved statistical precision extends coverage into lower momentum regions, providing detailed insight into these fundamental particle interactions.

Understanding the strong force, one of the four fundamental interactions governing the universe, requires detailed knowledge of the behaviour of gluons – the force carriers of this interaction. Recent research focuses on precisely mapping the interactions between gluons themselves, and between gluons and ghost particles – mathematical constructs essential for calculations in quantum field theory. Nuno Brito, from the Centre for Mathematical Sciences, University of Plymouth, and Manuel Colaço, Orlando Oliveira, and Paulo J. Silva, all from CFisUC, Department of Physics, University of Coimbra, present findings in their article, ‘The four-gluon and ghost-gluon vertices in the Landau gauge from lattice simulations’, detailing analysis of these interactions using large-scale numerical simulations. Their work provides refined data on gluon interactions, particularly in the challenging infrared region of momentum space, and extends previous results to a broader range of conditions.

Researchers employ high-statistics lattice Quantum Chromodynamics (QCD) calculations to refine understanding of the four-gluon and ghost-gluon vertices, fundamental components of the strong force governing interactions between quarks and gluons. These calculations yield improved coverage of the infrared (IR) region for the four-gluon vertex, extending previous work focused on collinear kinematics, and provide a more comprehensive description of gluon and ghost propagation.

The research details a precise determination of the one-particle irreducible ghost-gluon function, with particular emphasis on the soft gluon limit. This is significant because the ghost-gluon vertex is central to addressing the Gribov ambiguity – a challenge in defining the quantum field theory of the strong interaction – and elucidating the infrared behaviour of QCD.

Researchers investigated the behaviour of these vertices across various kinematic regimes, analysing the momentum dependence of interaction strengths. Lattice results are compared with predictions from perturbative calculations and, where available, with experimental data. Systematic attention is given to discretisation and finite volume effects, inherent limitations of lattice QCD calculations, to ensure the reliability of the extracted vertex values.

By precisely determining these vertices, the research contributes to a more complete understanding of the strong coupling constant and the dynamics of gluons and ghosts within QCD. Findings are disseminated through peer-reviewed publications and presentations at international conferences, furthering knowledge within the particle physics community. The research group continues to refine calculations and explore new avenues for understanding the strong force.