Periodic Reporting for period 1 - HiCoLat (High-precision computations on fine lattices)
Période du rapport: 2023-10-01 au 2025-09-30
One of the central goals of particle physics is to test how well the Standard Model describes nature. A particularly sensitive way to do this is through extremely precise measurements of particles’ magnetic properties. The muon, a heavier cousin of the electron, behaves like a tiny magnet. Experiments have measured this magnetic behavior, known as the muon magnetic moment, with stunning accuracy. To fully exploit this achievement, theorists must match this precision in their calculations. Only then can even tiny deviations reveal the presence of new, yet-undiscovered particles or interactions.
A key part of the theoretical prediction involves understanding how the strong force influences the muon. This contribution is called the hadronic vacuum polarization (HVP). It can only be calculated reliably using lattice quantum chromodynamics (lattice QCD), a numerical approach that simulates the strong force by representing space and time on a grid. However, these simulations are extremely demanding: achieving higher precision requires much finer and larger grids, which rapidly increases the computational effort needed to obtain reliable results.
The HiCoLat project set out to address this challenge. Its objective was to develop and apply improved computational methods that reduce noise and control systematic uncertainties in high-resolution lattice QCD simulations. With these enhanced tools, the project aimed to produce a more precise and reliable determination of the HVP contribution to the muon magnetic moment. In addition, the project explored how the same techniques could benefit other areas of particle physics, including studies of heavy quarks that play a role in current searches for physics beyond the Standard Model.
A key part of the theoretical prediction involves understanding how the strong force influences the muon. This contribution is called the hadronic vacuum polarization (HVP). It can only be calculated reliably using lattice quantum chromodynamics (lattice QCD), a numerical approach that simulates the strong force by representing space and time on a grid. However, these simulations are extremely demanding: achieving higher precision requires much finer and larger grids, which rapidly increases the computational effort needed to obtain reliable results.
The HiCoLat project set out to address this challenge. Its objective was to develop and apply improved computational methods that reduce noise and control systematic uncertainties in high-resolution lattice QCD simulations. With these enhanced tools, the project aimed to produce a more precise and reliable determination of the HVP contribution to the muon magnetic moment. In addition, the project explored how the same techniques could benefit other areas of particle physics, including studies of heavy quarks that play a role in current searches for physics beyond the Standard Model.
The project developed improved methods that make large-scale simulations of the strong force more precise and less affected by statistical noise. These advances made it possible to create a new, high-quality set of simulation data at very fine resolution, tailored to reproduce the properties of real-world particles as closely as possible.
Building on this progress, HiCoLat achieved one of the most precise calculations to date of the leading contribution of the strong force to the muon’s magnetic moment. This result has already been incorporated into the newest global Standard Model prediction, helping theoretical calculations keep pace with the outstanding precision reached by recent experiments.
The project also advanced work on additional contributions that will matter in the next generation of precision studies. This includes progress toward the next-to-leading-order strong-interaction effects and toward determining how the electroweak interaction strengths evolve at low energies — information that will be highly relevant for future collider programs. The new methods were further tested in first applications to heavy-quark physics, demonstrating their potential for broader use in upcoming research.
Building on this progress, HiCoLat achieved one of the most precise calculations to date of the leading contribution of the strong force to the muon’s magnetic moment. This result has already been incorporated into the newest global Standard Model prediction, helping theoretical calculations keep pace with the outstanding precision reached by recent experiments.
The project also advanced work on additional contributions that will matter in the next generation of precision studies. This includes progress toward the next-to-leading-order strong-interaction effects and toward determining how the electroweak interaction strengths evolve at low energies — information that will be highly relevant for future collider programs. The new methods were further tested in first applications to heavy-quark physics, demonstrating their potential for broader use in upcoming research.
HiCoLat has advanced the precision of theoretical predictions in one of the most closely watched areas of particle physics. By reducing key uncertainties in the HVP calculation, the project helps bring theoretical predictions closer to the extraordinary accuracy achieved by recent experiments. The project also demonstrated the effectiveness of new computational strategies that can be used more broadly in future lattice QCD studies. Continued research building on these methods will support even more precise tests of the Standard Model and further explorations of possible new physics.