Scattering lengths of the $J/ψπ$ and $J/ψK$ systems

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Main Authors: Yan, Jiang, Cao, Xiong-Hui, Du, Meng-Lin, Guo, Feng-Kun
Format: Preprint
Published: 2026
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author Yan, Jiang
Cao, Xiong-Hui
Du, Meng-Lin
Guo, Feng-Kun
author_facet Yan, Jiang
Cao, Xiong-Hui
Du, Meng-Lin
Guo, Feng-Kun
contents We investigate the low-energy interactions between the charmonium state $J/ψ$ and the light pseudoscalar mesons ($π$ and $K$) within the framework of dispersion relations.We demonstrate that the symmetry-breaking terms in the chiral Lagrangian induce mixing between the bare charmonium fields, necessitating a diagonalization procedure to correctly identify the physical $J/ψ$ and $ψ'$ states. Following this diagonalization, we relate the threshold scattering amplitudes of $J/ψ{\cal P}~({\cal P}=π,K)$, which determine the scattering lengths, to the $J/ψJ/ψ\to {\cal P}\bar{\cal P}$ amplitudes via crossing symmetry. The ${\cal P}\bar{\cal P}$ rescattering effects are incorporated using dispersion relations. We obtain the $S$-wave scattering lengths $a_{J/ψπ} \lesssim -0.0021$~fm and $a_{J/ψK} \lesssim -0.028$~fm, where the negative sign indicates an attractive interaction. Our results show that the $J/ψK$ interaction is moderately enhanced relative to the pion channel, driven by explicit chiral symmetry breaking. Furthermore, a quantitative comparison of the coupled-channel mechanism, where $J/ψπ$ couples to $D\bar{D}^*$ and $J/ψK$ couples to $D^*\bar{D}_s/D\bar{D}_s^*$, reveals that both $J/ψπ$ and $J/ψK$ scatterings are predominantly governed by the soft-gluon exchange mechanism.
format Preprint
id arxiv_https___arxiv_org_abs_2601_18103
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Scattering lengths of the $J/ψπ$ and $J/ψK$ systems
Yan, Jiang
Cao, Xiong-Hui
Du, Meng-Lin
Guo, Feng-Kun
High Energy Physics - Phenomenology
We investigate the low-energy interactions between the charmonium state $J/ψ$ and the light pseudoscalar mesons ($π$ and $K$) within the framework of dispersion relations.We demonstrate that the symmetry-breaking terms in the chiral Lagrangian induce mixing between the bare charmonium fields, necessitating a diagonalization procedure to correctly identify the physical $J/ψ$ and $ψ'$ states. Following this diagonalization, we relate the threshold scattering amplitudes of $J/ψ{\cal P}~({\cal P}=π,K)$, which determine the scattering lengths, to the $J/ψJ/ψ\to {\cal P}\bar{\cal P}$ amplitudes via crossing symmetry. The ${\cal P}\bar{\cal P}$ rescattering effects are incorporated using dispersion relations. We obtain the $S$-wave scattering lengths $a_{J/ψπ} \lesssim -0.0021$~fm and $a_{J/ψK} \lesssim -0.028$~fm, where the negative sign indicates an attractive interaction. Our results show that the $J/ψK$ interaction is moderately enhanced relative to the pion channel, driven by explicit chiral symmetry breaking. Furthermore, a quantitative comparison of the coupled-channel mechanism, where $J/ψπ$ couples to $D\bar{D}^*$ and $J/ψK$ couples to $D^*\bar{D}_s/D\bar{D}_s^*$, reveals that both $J/ψπ$ and $J/ψK$ scatterings are predominantly governed by the soft-gluon exchange mechanism.
title Scattering lengths of the $J/ψπ$ and $J/ψK$ systems
topic High Energy Physics - Phenomenology
url https://arxiv.org/abs/2601.18103