On the scalar $\pi K$ form factor beyond the elastic region

Pion-kaon ($\pi K$) final states, often appearing in heavy-particle decays at the precision frontier, are important for Standard-Model tests, to describe crossed channels with exotic states, and for spectroscopy of excited kaon resonances. We construct a representation of the $\pi K$ $S$-wave form f...

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Main Author: Frederic Noël, Leon von Detten, Christoph Hanhart, Martin Hoferichter, Bastian Kubis
Format: Article
Language:English
Published: SciPost 2025-07-01
Series:SciPost Physics Proceedings
Online Access:https://scipost.org/SciPostPhysProc.16.008
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author Frederic Noël, Leon von Detten, Christoph Hanhart, Martin Hoferichter, Bastian Kubis
author_facet Frederic Noël, Leon von Detten, Christoph Hanhart, Martin Hoferichter, Bastian Kubis
author_sort Frederic Noël, Leon von Detten, Christoph Hanhart, Martin Hoferichter, Bastian Kubis
collection DOAJ
description Pion-kaon ($\pi K$) final states, often appearing in heavy-particle decays at the precision frontier, are important for Standard-Model tests, to describe crossed channels with exotic states, and for spectroscopy of excited kaon resonances. We construct a representation of the $\pi K$ $S$-wave form factor using the elastic $\pi K$ scattering phase shift via dispersion relations in the elastic region and extend this model into the inelastic region using resonance exchange, while maintaining unitarity and the correct analytic structure. As a first application, we successfully described the $\tau \to K_S \pi \nu_\tau$ spectrum to not only achieve a better distinction between $S$- and $P$-wave contributions, but also to provide an improved estimate of the $CP$ asymmetry produced by a tensor operator as well as the forward-backward asymmetry, both of which can be confronted with future data at Belle II. The work presented here is published in [L. von Detten et al., Eur. Phys. J. C 81, 420 (2021)].
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spelling doaj-art-323f5dc8611b46dba7d4dd3943cb12082025-08-20T02:37:13ZengSciPostSciPost Physics Proceedings2666-40032025-07-011600810.21468/SciPostPhysProc.16.008On the scalar $\pi K$ form factor beyond the elastic regionFrederic Noël, Leon von Detten, Christoph Hanhart, Martin Hoferichter, Bastian KubisPion-kaon ($\pi K$) final states, often appearing in heavy-particle decays at the precision frontier, are important for Standard-Model tests, to describe crossed channels with exotic states, and for spectroscopy of excited kaon resonances. We construct a representation of the $\pi K$ $S$-wave form factor using the elastic $\pi K$ scattering phase shift via dispersion relations in the elastic region and extend this model into the inelastic region using resonance exchange, while maintaining unitarity and the correct analytic structure. As a first application, we successfully described the $\tau \to K_S \pi \nu_\tau$ spectrum to not only achieve a better distinction between $S$- and $P$-wave contributions, but also to provide an improved estimate of the $CP$ asymmetry produced by a tensor operator as well as the forward-backward asymmetry, both of which can be confronted with future data at Belle II. The work presented here is published in [L. von Detten et al., Eur. Phys. J. C 81, 420 (2021)].https://scipost.org/SciPostPhysProc.16.008
spellingShingle Frederic Noël, Leon von Detten, Christoph Hanhart, Martin Hoferichter, Bastian Kubis
On the scalar $\pi K$ form factor beyond the elastic region
SciPost Physics Proceedings
title On the scalar $\pi K$ form factor beyond the elastic region
title_full On the scalar $\pi K$ form factor beyond the elastic region
title_fullStr On the scalar $\pi K$ form factor beyond the elastic region
title_full_unstemmed On the scalar $\pi K$ form factor beyond the elastic region
title_short On the scalar $\pi K$ form factor beyond the elastic region
title_sort on the scalar pi k form factor beyond the elastic region
url https://scipost.org/SciPostPhysProc.16.008
work_keys_str_mv AT fredericnoelleonvondettenchristophhanhartmartinhoferichterbastiankubis onthescalarpikformfactorbeyondtheelasticregion