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arXiv · 2604.20439

QCD sum rule analysis of local meson-meson currents for the $K(1690)$ state

Yi-Qi Mu·Peng-Wen Xu·Si-Tong Chen·Yi-Tong Wei·Ge-Jia Zhang·Bing-Dong Wan
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Abstract

The nature of the recently observed $K(1690)$ state, reported by the COMPASS Collaboration as a candidate strange crypto-exotic meson with $J^P=0^-$, remains unclear. In this work, we investigate whether it can be described by local meson-meson currents within the framework of QCD sum rules. We construct a set of independent local color-singlet meson-meson interpolating currents with $J^P=0^-$ and analyze their QCD sum rules. For the currents that admit reliable Borel windows, the extracted effective mass scales are consistently in the range of $2.0$--$2.3~\mathrm{GeV}$, significantly above the experimental mass of the $K(1690)$. Within the standard pole-plus-continuum framework, none of the selected local currents yields a separately resolved low-lying pole compatible with the COMPASS signal. These results indicate that the selected local color-singlet meson-meson currents do not isolate the $K(1690)$ signal within the present framework, while leaving open the possibility of more extended molecular dynamics and other configurations beyond the present analysis.

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Yi-Qi Mu, Peng-Wen Xu, Si-Tong Chen, Yi-Tong Wei, Ge-Jia Zhang, Bing-Dong Wan. 2026-04-22. QCD sum rule analysis of local meson-meson currents for the $K(1690)$ state. https://doi.org/10.1088/1674-1137/aea108

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