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arXiv · 2501.08407

Impact of New Physics on Momentum-Dependent Particle Widths and Propagators

Christoph Englert·Wrishik Naskar·Michael Spannowsky
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Abstract

We investigate the impact of momentum-dependent particle widths and propagators on gauge and Higgs bosons and the top quark within the Standard Model (SM) and its SMEFT extensions near thresholds. By incorporating self-energy corrections via Dyson resummation, we quantify deviations from the fixed-width approximation and assess their implications for collider observables. While effects on the Higgs boson are negligible and the $W$ boson shows percent-level deviations in reconstructed transverse mass distributions, the top quark exhibits significant sensitivity near its mass threshold. Future lepton colliders, e.g., electron-positron machines or muon colliders, can offer sensitivity to these effects, enabling constraints on SMEFT Wilson coefficients. We perform a representative case study for the precision frontier available with a staged future muon collider. Our results highlight that momentum dependencies can provide additional sensitivity at precision-era experiments, enhancing the potential for discovering new physics there.

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Christoph Englert, Wrishik Naskar, Michael Spannowsky. 2025-01-14. Impact of New Physics on Momentum-Dependent Particle Widths and Propagators. https://doi.org/10.1103/physrevd.111.055017

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