Probing the Tau Anomalous Magnetic Moment at Colliders: From Ultra-Peripheral Collisions to the Precision Frontier
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arXiv
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| Natura: | Preprint |
| Pubblicazione: |
2026
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| _version_ | 1866908984820105216 |
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| author | Vignaroli, Natascia |
| author_facet | Vignaroli, Natascia |
| contents | The anomalous magnetic moment of the tau lepton, $a_τ$, represents a fundamental test of the Standard Model (SM) and a high-sensitivity probe for New Physics in the third generation of leptons. Due to the tau's extremely short lifetime, traditional spin-precession measurements remain inaccessible, necessitating innovative experimental strategies at high-energy colliders. This review provides a comprehensive overview of the current experimental landscape, highlighting the recent paradigm shift from LEP-era constraints to the unprecedented precision reached at the LHC. We emphasize the importance of Ultra-Peripheral Heavy-Ion Collisions (UPCs), which act as a ``photon-photon collider'' of extreme intensity. By leveraging the $Z^4$ enhancement of the coherent photon flux in Lead-Lead ($PbPb$) interactions, these collisions provide a theoretically robust ``quasi-static'' environment. These results are critically compared with the latest measurements from proton-proton collisions, including the recent CMS observation of the $γγ\to ττ$ process and the ATLAS constraints from the high-mass Drell-Yan tail. We evaluate their complementarity and the challenges related to Effective Field Theory validity at the TeV scale. Finally, we outline the future prospects for $a_τ$ at Belle II and the Future Circular Collider (FCC) stages. While FCC-hh in $PbPb$ mode provides a theoretically clean environment, its sensitivity remains limited to $\mathcal{O}(10^{-2})$. Conversely, the next generation of lepton facilities, specifically Belle II and FCC-ee, aims for the $\mathcal{O}(10^{-5})$ level, required to probe SM electroweak loop corrections. Long-term projections for a high-energy Muon Collider suggest a potential reach of $\mathcal{O}(10^{-6})$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_19665 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Probing the Tau Anomalous Magnetic Moment at Colliders: From Ultra-Peripheral Collisions to the Precision Frontier Vignaroli, Natascia High Energy Physics - Phenomenology High Energy Physics - Experiment The anomalous magnetic moment of the tau lepton, $a_τ$, represents a fundamental test of the Standard Model (SM) and a high-sensitivity probe for New Physics in the third generation of leptons. Due to the tau's extremely short lifetime, traditional spin-precession measurements remain inaccessible, necessitating innovative experimental strategies at high-energy colliders. This review provides a comprehensive overview of the current experimental landscape, highlighting the recent paradigm shift from LEP-era constraints to the unprecedented precision reached at the LHC. We emphasize the importance of Ultra-Peripheral Heavy-Ion Collisions (UPCs), which act as a ``photon-photon collider'' of extreme intensity. By leveraging the $Z^4$ enhancement of the coherent photon flux in Lead-Lead ($PbPb$) interactions, these collisions provide a theoretically robust ``quasi-static'' environment. These results are critically compared with the latest measurements from proton-proton collisions, including the recent CMS observation of the $γγ\to ττ$ process and the ATLAS constraints from the high-mass Drell-Yan tail. We evaluate their complementarity and the challenges related to Effective Field Theory validity at the TeV scale. Finally, we outline the future prospects for $a_τ$ at Belle II and the Future Circular Collider (FCC) stages. While FCC-hh in $PbPb$ mode provides a theoretically clean environment, its sensitivity remains limited to $\mathcal{O}(10^{-2})$. Conversely, the next generation of lepton facilities, specifically Belle II and FCC-ee, aims for the $\mathcal{O}(10^{-5})$ level, required to probe SM electroweak loop corrections. Long-term projections for a high-energy Muon Collider suggest a potential reach of $\mathcal{O}(10^{-6})$. |
| title | Probing the Tau Anomalous Magnetic Moment at Colliders: From Ultra-Peripheral Collisions to the Precision Frontier |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2604.19665 |