Quantum properties of heavy-fermion pairs at a lepton collider with polarised beams
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arXiv
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| Autori principali: | , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2026
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| _version_ | 1866918307386359808 |
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| author | Altakach, Mohammad Mahdi Lamba, Priyanka Maltoni, Fabio Sakurai, Kazuki |
| author_facet | Altakach, Mohammad Mahdi Lamba, Priyanka Maltoni, Fabio Sakurai, Kazuki |
| contents | We investigate the quantum properties of heavy-fermion pairs, such as $t\bar t$ or $τ^+τ^-$, produced in lepton-lepton collisions with polarised beams. Focusing on spin correlations, entanglement, Bell-inequality violation, and quantum-information-theoretic measures such as purity and magic, we analyse how beam polarisation shapes the structure of the spin-density matrix. We derive analytic expressions for a wide range of helicity configurations, including both Standard Model contributions and generic new-physics effects parametrised by scalar, vector, and tensor four-fermion operators within an effective field theory framework. We show that beam polarisation unlocks a substantially richer set of spin configurations and significantly enhances sensitivity to non-standard interactions. As a phenomenological application, we study $t\bar t$ production at a future linear collider and demonstrate that quantum observables provide a comprehensive and complementary probe of top-quark interactions and stronger constraints on the scale of new physics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_09558 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Quantum properties of heavy-fermion pairs at a lepton collider with polarised beams Altakach, Mohammad Mahdi Lamba, Priyanka Maltoni, Fabio Sakurai, Kazuki High Energy Physics - Phenomenology High Energy Physics - Experiment High Energy Physics - Theory Quantum Physics We investigate the quantum properties of heavy-fermion pairs, such as $t\bar t$ or $τ^+τ^-$, produced in lepton-lepton collisions with polarised beams. Focusing on spin correlations, entanglement, Bell-inequality violation, and quantum-information-theoretic measures such as purity and magic, we analyse how beam polarisation shapes the structure of the spin-density matrix. We derive analytic expressions for a wide range of helicity configurations, including both Standard Model contributions and generic new-physics effects parametrised by scalar, vector, and tensor four-fermion operators within an effective field theory framework. We show that beam polarisation unlocks a substantially richer set of spin configurations and significantly enhances sensitivity to non-standard interactions. As a phenomenological application, we study $t\bar t$ production at a future linear collider and demonstrate that quantum observables provide a comprehensive and complementary probe of top-quark interactions and stronger constraints on the scale of new physics. |
| title | Quantum properties of heavy-fermion pairs at a lepton collider with polarised beams |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment High Energy Physics - Theory Quantum Physics |
| url | https://arxiv.org/abs/2601.09558 |