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Limitations of quantum tomography in Higgs-boson decays to four leptons
Abstract
We investigate the limitations of the two-qutrit quantum tomography in Higgs-boson decays to four charged leptons. At next-to-leading order, the standard reconstruction can yield an operator that is not positive semidefinite, even when radiatively improved spin-analysing powers are used. We trace this failure to the coherent combination of photon- and Z-mediated contributions to the off-shell dilepton system, whose distinct production and decay structures invalidate the assumed universal decay analysers. Nevertheless, the rank-two angular sector remains accessible and perturbatively stable, enabling a robust lower bound on the squared concurrence, and hence a reliable assessment of entanglement beyond leading order.
Related
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- Analysis of the CP structure of the Yukawa coupling between the Higgs boson and tau leptons in proton-proton collisions at √s=13.6 TeV
BibTeX
@misc{gratta2026limitations,
title = {{Limitations of quantum tomography in Higgs-boson decays to four leptons}},
author = {Morgan Del Gratta and Fabio Maltoni and Davide Pagani and Giovanni Pelliccioli},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25217},
eprint = {2609.25217},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25217},
}
RIS
TY - UNPB
TI - Limitations of quantum tomography in Higgs-boson decays to four leptons
AU - Morgan Del Gratta
AU - Fabio Maltoni
AU - Davide Pagani
AU - Giovanni Pelliccioli
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.25217
UR - https://arxiv.org/abs/2609.25217
AB - We investigate the limitations of the two-qutrit quantum tomography in Higgs-boson decays to four charged leptons. At next-to-leading order, the standard reconstruction can yield an operator that is not positive semidefinite, even when radiatively improved spin-analysing powers are used. We trace this failure to the coherent combination of photon- and Z-mediated contributions to the off-shell dilepton system, whose distinct production and decay structures invalidate the assumed universal decay analysers. Nevertheless, the rank-two angular sector remains accessible and perturbatively stable, enabling a robust lower bound on the squared concurrence, and hence a reliable assessment of entanglement beyond leading order.
ER -