Precision Physics in Finite and Infinite Volume
Lead Research Organisation:
University of Edinburgh
Department Name: Sch of Physics and Astronomy
Abstract
The Standard Model (SM) of particle physics has had great success in its many predictions, but in certain cases there appears to be
tension with experimental measurements. These discrepancies could be hints of physics hitherto unknown, so it is of great
importance to discover all flaws in the model. In this two-year project I will do timely and ambitious low-energy SM calculations
needed for precision tests that in the future can guide in the search for a new model.
This project is divided in two areas. The first focusses on flavour physics where quark interactions lead to
charge-parity violation, a phenomenon connected to the matter-antimatter asymmetry of the Universe. I will
here study kaon decays in a finite-volume spacetime, including electromagnetic corrections. The major focus point will be how to
analytically convert finite-volume lattice results for these kaon decays to physical predictions. A key intermediate step will be the
understanding of pion-pion scattering including electromagnetic corrections, which on its own also is of interest for extraction of
scattering parameters from the lattice.
The second focus area concerns the muon magnetic moment for which a possible discrepancy with experiments has been
discovered. The main focus here will be on analytical calculations to reduce the error on the SM prediction. In one sub-project we will
derive the leading structure-dependent finite-volume effects for the hadronic vacuum polarisation allowing for future improved
precision tests from lattice QCD+QED of the quantity in question. In the other sub-project we will derive short-distance constraints on
the electroweak contribution to the muon magnetic moment with the help of the operator product expansion. These short-distance
constraints will reduce the current uncertainty on the electroweak contribution.
tension with experimental measurements. These discrepancies could be hints of physics hitherto unknown, so it is of great
importance to discover all flaws in the model. In this two-year project I will do timely and ambitious low-energy SM calculations
needed for precision tests that in the future can guide in the search for a new model.
This project is divided in two areas. The first focusses on flavour physics where quark interactions lead to
charge-parity violation, a phenomenon connected to the matter-antimatter asymmetry of the Universe. I will
here study kaon decays in a finite-volume spacetime, including electromagnetic corrections. The major focus point will be how to
analytically convert finite-volume lattice results for these kaon decays to physical predictions. A key intermediate step will be the
understanding of pion-pion scattering including electromagnetic corrections, which on its own also is of interest for extraction of
scattering parameters from the lattice.
The second focus area concerns the muon magnetic moment for which a possible discrepancy with experiments has been
discovered. The main focus here will be on analytical calculations to reduce the error on the SM prediction. In one sub-project we will
derive the leading structure-dependent finite-volume effects for the hadronic vacuum polarisation allowing for future improved
precision tests from lattice QCD+QED of the quantity in question. In the other sub-project we will derive short-distance constraints on
the electroweak contribution to the muon magnetic moment with the help of the operator product expansion. These short-distance
constraints will reduce the current uncertainty on the electroweak contribution.
Publications
Anzivino G
(2024)
Workshop summary: Kaons@CERN 2023
in The European Physical Journal C
Bijnens J
(2024)
The anomalous chiral Lagrangian at order p8
in Journal of High Energy Physics
Hermansson-Truedsson N
(2025)
Structure-dependent electromagnetic finite-volume effects to the hadronic vacuum polarisation
Ruiz-Vidal J
(2024)
The anomalous Lagrangian in ChPT at NNLO
| Description | There are several significant achievements associated to the work in this grant. The major goals of the project were to address systematic effects in calculations of kaon/pion decays as well as the muon anomalous magnetic moment (muon g-2). Specifically, the aim was to consider electromagnetic corrections in finite-volume lattice QCD calculations (decays and g-2) as well as short-distance effects (g-2). This is highly important for precision tests of the Standard Model of particle physics. Short-distance constraints were derived for the muon g-2, specifically the hadronic light-by-light contribution (https://inspirehep.net/literature/2848348), and new methodology developed. A major cancellation in the constraints was observed, which turned out to be highly impactful for a future theoretical prediction of the hadronic light-by-light contribution reaching the community precision goal. Without the gained knowledge of the work here, it is unlikely that the goal would be reached within the foreseeable future. Also finite-volume effects associated to electromagnetic effects in the muon g-2 hadronic vacuum polarisation were investigated (https://inspirehep.net/literature/2818229). A strategy was developed to determine them, in particular a highly non-trivial structure-dependent quantity known as the branch-cut. Without determining this, it is difficult to estimate the leading finite-volume effects in the QED prescription QED_L. Branch-cuts in general appear in all observables. From investigations of electromagnetic finite-volume effects in decays of kaons and pions, a strategy was developed to eliminate the non-trivial structure-dependent branch-cut contributions for leptonic decays. The developed solution (https://inspirehep.net/literature/2868860) was to develop a new QED prescription, QED_r. This generic prescription is a promising method to remove complicated branch-cuts in a variety of processes, including the muon g-2. Work was also undertaken within the RBC/UKQCD lattice collaboration for a novel prediction for the g-2 hadronic vacuum polarisation (https://inspirehep.net/literature/2843080). Finally, an effective anomalous Lagrangian for chiral perturbation theory was derived (https://inspirehep.net/literature/2715824). This can be used for estimating structure-dependent form factors appearing in a variety of calculations, e.g. decays of pions and kaons. The various achievements in this proposal pave the way for future precision tests of the Standard Model in the search for new physics particles. |
| Exploitation Route | The achievements in this project are particularly relevant for other practitioners in the field, both in terms of developed methodology and beyond. Important findings were made for improved precision tests of the Standard Model, in the search for new physics. The work is particularly relevant for both the muon g-2 and kaon decays, the latter discussed in the workshop summary (https://inspirehep.net/literature/2719296) where the project results are highly important. |
| Sectors | Other |
| Description | From the broader non-scientific perspective, the project provides a science case for continued developments in high-performance computing through large scale lattice simulations. This field in particular connects academia and industry, thus promoting a need for continued technological advancement and investment in both computing and training of technical staff. The generated knowledge from the findings of the project also provides new input for teaching and outreach, which will attract new students to study at university level and thus have long-term societal impact. |
| Sector | Digital/Communication/Information Technologies (including Software) |
| Impact Types | Societal |
| Title | Anomalous chiral perturbation theory Lagrangian at order p^8 |
| Description | Fully generic anomalous chiral perturbation theory Lagrangian at order p^8, developed in collaboration between Edinburgh and Lund. The associated paper is published in Journal of High-Energy Physics with doi 10.1007/JHEP01(2024)009 |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2023 |
| Provided To Others? | Yes |
| Impact | The Lagrangian derived is general and can be used for anyone interested in higher-order chiral perturbation theory calculations. This is relevant to e.g. estimate structure-dependent form factors appearing in a variety of calculations, such as decays of pions and kaons. |
| Title | QEDr: An improved prescription for electromagnetic effects in lattice QCD |
| Description | This is a new QED prescription developed in Edinburgh and CERN. The associated paper is submitted to a scientific journal. The preprint is available at https://arxiv.org/abs/2501.07936 |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2025 |
| Provided To Others? | Yes |
| Impact | Our findings indicate that the QEDr prescription conveniently removes a previous precision bottleneck associate to finite-volume effects in lattice QCD calculations, thus allowing for future improved precision tests of the Standard Model. It is a generic method that we expect to benefit a broad group of practitioners in the field, in the UK and beyond. |
| URL | https://arxiv.org/abs/2501.07936 |
| Description | Chiral perturbation theory Lagrangian |
| Organisation | Lund University |
| Department | Department of Physics |
| Country | Sweden |
| Sector | Academic/University |
| PI Contribution | Together with J. Bijnens and J. Ruiz-Vidal, N. Hermansson-Truedsson derived the effective anomalous chiral perturbation theory Lagrangian at order p^8. NHT did all the calculations independently, primarily using the computer software FORM. |
| Collaborator Contribution | Each collaborator did the calculations independently. |
| Impact | One paper (doi = "10.1007/JHEP01(2024)009") and one set of proceedings (DOI: 10.22323/1.449.0509). This is not multi-disciplinary. |
| Start Year | 2023 |
| Description | Finite-volume QED calculations |
| Organisation | European Organization for Nuclear Research (CERN) |
| Department | CERN - Other |
| Country | Switzerland |
| Sector | Academic/University |
| PI Contribution | We investigate electromagnetic corrections to various observables calculated in lattice simulations. One particular focus was leptonic decay rates and masses of kaons and pions. Nils Hermansson-Truedsson is involved in both numerical and analytical calculations. |
| Collaborator Contribution | The collaborators Matteo Di Carlo, Maxwell Hansen and Antonin Portelli (PI of the award) are all deeply involved in the work, which can be split in different projects. Several collaborators do the same calculations for cross-checks, and everyone contributes with essential ideas/input. |
| Impact | One paper submitted to a scientific journal (https://inspirehep.net/literature/2868860). Proceedings (DOI: 10.22323/1.466.0267, DOI: 10.22323/1.453.0265) This is not multi-disciplinary. |
| Start Year | 2019 |
| Description | Finite-volume QED calculations |
| Organisation | University of Edinburgh |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | We investigate electromagnetic corrections to various observables calculated in lattice simulations. One particular focus was leptonic decay rates and masses of kaons and pions. Nils Hermansson-Truedsson is involved in both numerical and analytical calculations. |
| Collaborator Contribution | The collaborators Matteo Di Carlo, Maxwell Hansen and Antonin Portelli (PI of the award) are all deeply involved in the work, which can be split in different projects. Several collaborators do the same calculations for cross-checks, and everyone contributes with essential ideas/input. |
| Impact | One paper submitted to a scientific journal (https://inspirehep.net/literature/2868860). Proceedings (DOI: 10.22323/1.466.0267, DOI: 10.22323/1.453.0265) This is not multi-disciplinary. |
| Start Year | 2019 |
| Description | Muon g-2: Hadronic light-by-light |
| Organisation | Lund University |
| Department | Department of Physics |
| Country | Sweden |
| Sector | Academic/University |
| PI Contribution | Together with J. Bijnens and A. Rodríguez-Sánchez, Nils Hermansson-Truedsson did calculations for the muon g-2 contribution known as the hadronic light-by-light. NHT independently did all calculations. The technology used was the operator product expansion. |
| Collaborator Contribution | The collaborators did all calculations as well, using the operator product expansion. |
| Impact | One paper accepted in Journal of High-Energy Physics (https://inspirehep.net/literature/2848348). This is not multi-disciplinary |
| Start Year | 2018 |
| Description | Muon g-2: Hadronic light-by-light |
| Organisation | University of Valencia |
| Country | Spain |
| Sector | Academic/University |
| PI Contribution | Together with J. Bijnens and A. Rodríguez-Sánchez, Nils Hermansson-Truedsson did calculations for the muon g-2 contribution known as the hadronic light-by-light. NHT independently did all calculations. The technology used was the operator product expansion. |
| Collaborator Contribution | The collaborators did all calculations as well, using the operator product expansion. |
| Impact | One paper accepted in Journal of High-Energy Physics (https://inspirehep.net/literature/2848348). This is not multi-disciplinary |
| Start Year | 2018 |
| Description | RBC/UKQCD g-2 |
| Organisation | University of Edinburgh |
| Department | School of Physics and Astronomy |
| Country | United Kingdom |
| Sector | Academic/University |
| PI Contribution | Nils Hermansson- Truedsson was involved in the analysis of the muon g-2 lattice simulation, involving several team members in Edinburgh, Southampton and CERN. The contribution of NHT was to study finite-volume effects to extract physical information from the simulations. |
| Collaborator Contribution | The collaborators performed other parts of the analysis and everyone discussed the different parts together. |
| Impact | The paper (https://inspirehep.net/literature/2843080) has been submitted to a scientific journal. This is not a multi-disciplinary collaboration. |
| Start Year | 2023 |
| Description | Invited colloquium Lund University |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Invited colloquium entitled ''Searching for new physics particles with low-energy precision calculations" by Nils Hermansson-Truedsson. The talk inspired many general questions about particle physics afterwards. |
| Year(s) Of Engagement Activity | 2024 |
| Description | Invited seminar Aix Marseille Université |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Invited seminar entitled 'QEDr: an infrared-improved finite-volume prescription' by Nils Hermansson-Truedsson. The seminar sparked lively discussion with local researchers afterwards |
| Year(s) Of Engagement Activity | 2024 |
| Description | Invited seminar Paul Scherrer Institute, Switzerland |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Invited seminar entitled 'Standard Model precision tests from the muon g - 2 and CKM matrix elements' by Nils Hermansson-Truedsson. The talk inspired many questions afterwards. |
| Year(s) Of Engagement Activity | 2024 |
| Description | Invited seminar Riken Centre for Computational Science |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Invited seminar entitled 'Short-distance constraints on the hadronic light-by-light' by Nils Hermansson-Truedsson. The seminar lead to many questions about the methods used and future studies. |
| Year(s) Of Engagement Activity | 2024 |
| Description | Invited seminar Swansea University |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | Invited seminar entitled 'Standard Model precision tests from the hadronic vacuum polarisation' by Nils Hermansson-Truedsson about recent work. The talk inspired many questions. |
| Year(s) Of Engagement Activity | 2024 |
| Description | Invited seminar University of Southampton |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | An invited seminar entitled 'Leptonic decay rates and finite-volume QED' presenting my recent work with collaborators in Edinburgh, by Nils Hermansson-Truedsson. Before the seminar I gave a 15 minute introduction to effective and lattice field theory to postgraduate students. After the seminar discussions continued about the topic with local researchers. |
| Year(s) Of Engagement Activity | 2023 |
| Description | Invited talk at Dirac Day 2024, Cardiff |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Professional Practitioners |
| Results and Impact | Invited science talk at Dirac Day 2024, entitled 'Precision tests of the Standard Model using lattice QCD' by Nils Hermansson-Truedsson. At this meeting participants from science and industry interact to discuss supercomputing in the UK. My talk inspired many questions afterwards. |
| Year(s) Of Engagement Activity | 2024 |
| URL | https://dirac.ac.uk/dirac-day-2024/ |
| Description | Invited talk at Mainz Institute for Theoretical Physics |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Invited seminar entitled 'Electromagnetic finite-size effects in the hadronic vacuum polarisation' at specialised workshop about isospin-breaking effects, by Nils Hermansson-Truedsson. The talk sparked a lot of discussion afterwards. |
| Year(s) Of Engagement Activity | 2024 |
| Description | Invited talk at g-2 plenary workshop at KEK in Tsukuba, Japan |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Invited talk entitled 'Short-distance constraints in the Melnikov-Vainshtein limit', at the yearly g-2 workshop, by Nils Hermansson-Truedsson. The talk inspired many questions afterwards |
| Year(s) Of Engagement Activity | 2024 |
| URL | https://conference-indico.kek.jp/event/257/ |