dorsal/arxiv
View SchemaQuantum properties of heavy-fermion pairs at a lepton collider with polarised beams
| Authors | Mohammad Mahdi Altakach, Priyanka Lamba, Fabio Maltoni, Kazuki Sakurai |
|---|---|
| Categories | |
| ArXiv ID | 2601.09558vv2 |
| URL | https://arxiv.org/abs/2601.09558 |
| License | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
Abstract
We investigate the quantum properties of heavy-fermion pairs, such as $t\bar t$ or $\tau^+\tau^-$, 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.
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"abstract": "We investigate the quantum properties of heavy-fermion pairs, such as $t\\bar t$ or $\\tau^+\\tau^-$, 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.",
"arxiv_id": "2601.09558",
"authors": [
"Mohammad Mahdi Altakach",
"Priyanka Lamba",
"Fabio Maltoni",
"Kazuki Sakurai"
],
"categories": [
"hep-ph",
"hep-ex",
"hep-th",
"quant-ph"
],
"license": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
"title": "Quantum properties of heavy-fermion pairs at a lepton collider with polarised beams",
"url": "https://arxiv.org/abs/2601.09558",
"version": "v2"
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