Emergence of kaonium as a sharp resonance in photon-photon to meson-meson cross-sections

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Main Authors: Beygi, Alireza, Klevansky, S. P., Lemmer, R. H.
Format: Preprint
Published: 2025
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author Beygi, Alireza
Klevansky, S. P.
Lemmer, R. H.
author_facet Beygi, Alireza
Klevansky, S. P.
Lemmer, R. H.
contents We calculate the binding energies of the hypothetical mesonic atom, $K^+ K^-$ (kaonium), using the $K^+ K^- \to K^+ K^-$ elastic scattering amplitude. Our findings are in line with previously reported results, which involve solving an eigenvalue equation of the Kudryavtsev-Popov type. Using chiral perturbation theory, we show that kaonium manifests itself as a sharp resonance around 992 MeV accompanying $f_0 (980)$ or $a_0 (980)$ in cross-sections for processes $γγ\to π^0 π^0$ or $γγ\to π^0 η$. The latter process is particularly striking: the peak at the kaonium resonance energy is highly pronounced, with the ratio of the cross-sections $σ(γγ\to π^0 η) / σ(γγ\to π^0 π^0) \approx 9$. Due to the short lifetime of kaonium ($\sim 10^{-18}$ s) and its small decay width ($\sim 0.4$ keV), direct detection of this exotic atom poses a significant challenge and requires high experimental resolution. However, we show that once the formation of kaonium is considered in the cross-section, a better fit to the available experimental data is obtained.
format Preprint
id arxiv_https___arxiv_org_abs_2511_04392
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Emergence of kaonium as a sharp resonance in photon-photon to meson-meson cross-sections
Beygi, Alireza
Klevansky, S. P.
Lemmer, R. H.
High Energy Physics - Phenomenology
Nuclear Theory
We calculate the binding energies of the hypothetical mesonic atom, $K^+ K^-$ (kaonium), using the $K^+ K^- \to K^+ K^-$ elastic scattering amplitude. Our findings are in line with previously reported results, which involve solving an eigenvalue equation of the Kudryavtsev-Popov type. Using chiral perturbation theory, we show that kaonium manifests itself as a sharp resonance around 992 MeV accompanying $f_0 (980)$ or $a_0 (980)$ in cross-sections for processes $γγ\to π^0 π^0$ or $γγ\to π^0 η$. The latter process is particularly striking: the peak at the kaonium resonance energy is highly pronounced, with the ratio of the cross-sections $σ(γγ\to π^0 η) / σ(γγ\to π^0 π^0) \approx 9$. Due to the short lifetime of kaonium ($\sim 10^{-18}$ s) and its small decay width ($\sim 0.4$ keV), direct detection of this exotic atom poses a significant challenge and requires high experimental resolution. However, we show that once the formation of kaonium is considered in the cross-section, a better fit to the available experimental data is obtained.
title Emergence of kaonium as a sharp resonance in photon-photon to meson-meson cross-sections
topic High Energy Physics - Phenomenology
Nuclear Theory
url https://arxiv.org/abs/2511.04392