Data-based form factor corrections between the two-pion τ and e⁺e^- spectral functions

2025/04/18 by Davier, Michel, Malaescu, Bogdan, Zhang, Zhiqing · 2 citations
#FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Phenomenology (hep-ph)

paper · doi:10.48550/arxiv.2504.13789

Abstract

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.

Citations

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Related

• Compatibility between e⁺e^- and τ decay data in the di-pion channel and implications for a_μ^SM and CVC tests
• On the inclusion of the pion form factor in e⁺e^- → π⁺π^- beyond leading order
• Radiative corrections to τ→ππν_τ
• Puzzles in the hadronic contributions to the muon anomalous magnetic moment
• Dispersive analysis of the pion vector form factor without zeros