Cottini, Martina (2025). Dispersive approach to the calculation of isospin–breaking corrections to ππ–scattering and τ− →π−π0ν. (Thesis). Universität Bern, Bern
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Abstract
The theoretical uncertainty of the anomalous magnetic moment of the muon Standard Model (SM) prediction, aμ, is dominated by hadronic inputs, more precisely by the hadronic vacuum polarization (HVP) contribution. The increased tension between the e+e− → π+π− measurements as well as the discrepancy between the data–driven approach and the lattice QCD result requires further investigation. On one side, a model independent approach for the isospin–breaking (IB) effects in the ππ–scattering amplitude can help clarifying the current situation. In this work, we derive the modifications to the Roy equations for ππ–scattering due to the charged–neutral pion mass difference, which is a first step towards a full dispersive calculation of the radiative corrections for the process e+e− → π+π−. On the other side, the hadronic τ decay, τ → ππ0ντ , provides an independent way to compute the HVP contribution to aμ. Here we will present a dispersive approach to the evaluation of the IB corrections relating τ → ππ0ντ to e+e− → π+π−, with a focus on the long–range corrections usually denoted by GEM(s).
| Item Type: | Thesis |
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| Dissertation Type: | Single |
| Date of Defense: | 8 December 2025 |
| Subjects: | 500 Science > 530 Physics |
| Institute / Center: | 08 Faculty of Science > Institute of Theoretical Physics |
| Depositing User: | Hammer Igor |
| Date Deposited: | 23 Jan 2026 11:42 |
| Last Modified: | 23 Jan 2026 11:42 |
| URI: | https://boristheses.unibe.ch/id/eprint/7073 |
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