Data-based form factor corrections between the two-pion $τ$ and $e^+e^-$ spectral functions
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| Format: | Preprint |
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2025
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| _version_ | 1866910914134933504 |
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| author | Davier, Michel Malaescu, Bogdan Zhang, Zhiqing |
| author_facet | Davier, Michel Malaescu, Bogdan Zhang, Zhiqing |
| contents | The $τ$ spectral functions are an alternative to $e^+e^-$ cross-sections, where different measurements are not consistent, for computing the hadronic vacuum contribution to the muon magnetic anomaly $a_μ$. This requires a control of isospin-breaking effects which have to be corrected for. So far these corrections have been evaluated using theoretical models. In this letter, a new approach based only on data is presented for the determination of the most critical correction relating the $e^+e^-$ and $τ$ pion form factors. An updated evaluation of the total isospin-breaking correction is given and its impact is discussed in the context of $e^+e^-$-based $a_μ$ predictions and of the direct measurement. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_13789 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Data-based form factor corrections between the two-pion $τ$ and $e^+e^-$ spectral functions Davier, Michel Malaescu, Bogdan Zhang, Zhiqing High Energy Physics - Phenomenology High Energy Physics - Experiment The $τ$ spectral functions are an alternative to $e^+e^-$ cross-sections, where different measurements are not consistent, for computing the hadronic vacuum contribution to the muon magnetic anomaly $a_μ$. This requires a control of isospin-breaking effects which have to be corrected for. So far these corrections have been evaluated using theoretical models. In this letter, a new approach based only on data is presented for the determination of the most critical correction relating the $e^+e^-$ and $τ$ pion form factors. An updated evaluation of the total isospin-breaking correction is given and its impact is discussed in the context of $e^+e^-$-based $a_μ$ predictions and of the direct measurement. |
| title | Data-based form factor corrections between the two-pion $τ$ and $e^+e^-$ spectral functions |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2504.13789 |