Z-boson quantum tomography at next-to-leading order
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arXiv
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| Autori principali: | , , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866908557033603072 |
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| author | Del Gratta, Morgan Fabbri, Federica Grossi, Michele Maltoni, Fabio Pagani, Davide Pelliccioli, Giovanni Vicini, Alessandro |
| author_facet | Del Gratta, Morgan Fabbri, Federica Grossi, Michele Maltoni, Fabio Pagani, Davide Pelliccioli, Giovanni Vicini, Alessandro |
| contents | We investigate the origin of the unusually large electroweak (EW) radiative effects observed in the extraction of the spin-density matrix and related observables at colliders, focusing on leptonic Z-boson decays. We compute the Z-boson-decay spin-density matrix at next-to-leading order (NLO) and find that, while its analytic structure remains essentially unchanged with respect to leading order, the EW corrections induce a sizeable $-35\%$ shift in the spin-analysing-power parameter $η_\ell$. This effect alone accounts for the striking size of the corrections. For boosted Z bosons, we further show that the treatment of photon radiation in lepton-dressing algorithms significantly affects the extraction of spin-density-matrix coefficients at NLO and must be carefully controlled. To address these challenges, we propose a quantum tomography procedure that is applicable to any final state with one or more on-shell Z bosons that is robust under higher-order corrections. We illustrate its validity and limitations in ${\textrm{pp}} \to {\textrm{ZZ}} \to 4\ell$ and in heavy ($M_{\textrm{H}}>2 M_{\textrm{Z}}$) Higgs-boson decay ${\textrm{H}}\to {\textrm{ZZ}} \to 4\ell$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_20456 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Z-boson quantum tomography at next-to-leading order Del Gratta, Morgan Fabbri, Federica Grossi, Michele Maltoni, Fabio Pagani, Davide Pelliccioli, Giovanni Vicini, Alessandro High Energy Physics - Phenomenology High Energy Physics - Experiment We investigate the origin of the unusually large electroweak (EW) radiative effects observed in the extraction of the spin-density matrix and related observables at colliders, focusing on leptonic Z-boson decays. We compute the Z-boson-decay spin-density matrix at next-to-leading order (NLO) and find that, while its analytic structure remains essentially unchanged with respect to leading order, the EW corrections induce a sizeable $-35\%$ shift in the spin-analysing-power parameter $η_\ell$. This effect alone accounts for the striking size of the corrections. For boosted Z bosons, we further show that the treatment of photon radiation in lepton-dressing algorithms significantly affects the extraction of spin-density-matrix coefficients at NLO and must be carefully controlled. To address these challenges, we propose a quantum tomography procedure that is applicable to any final state with one or more on-shell Z bosons that is robust under higher-order corrections. We illustrate its validity and limitations in ${\textrm{pp}} \to {\textrm{ZZ}} \to 4\ell$ and in heavy ($M_{\textrm{H}}>2 M_{\textrm{Z}}$) Higgs-boson decay ${\textrm{H}}\to {\textrm{ZZ}} \to 4\ell$. |
| title | Z-boson quantum tomography at next-to-leading order |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2509.20456 |