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arXiv · 2507.05726

Unraveling $K(1690)$ as a pseudoscalar $ud\bar{d}\bar{s}$ tetraquark state

Jin-Peng Zhang·Xu-Liang Chen·Zi-Xi Ou-Yang·Xiang Yu·Wei Chen·Jia-Jun Wu
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Abstract

The recent observed $K (1690)$ has been identified as a supernumerary pseudoscalar resonance signal in the strange-meson spectrum predicted by quark model calculations. It is the best candidate of a strange crypto-exotic state. In this work, we systematically study the hadron masses of $ud\bar{d}\bar{s}$ tetraquark states with $J^P = 0^-$ in the method of QCD sum rules (QCDSR). For ten interpolating currents, we calculate the correlation functions up to dimension-8 nonperturbative condensates. To calculate the tri-gluon condensate, we comprehensively consider the contributions from different operators with and without covariant derivatives. The infrared (IR) safety can be guaranteed for the completely calculated tri-gluon condensate by properly addressing the IR divergences in Feynman diagrams. It is demonstrated that the tri-gluon condensate provides significant contributions to the sum-rule analyses in these light tetraquark systems. Our results support the interpretation of $K (1690)$ resonance to be a pseudoscalar $ud\bar{d}\bar{s}$ tetraquark state.

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Jin-Peng Zhang, Xu-Liang Chen, Zi-Xi Ou-Yang, Xiang Yu, Wei Chen, Jia-Jun Wu. 2025-07-08. Unraveling $K(1690)$ as a pseudoscalar $ud\bar{d}\bar{s}$ tetraquark state. https://doi.org/10.1103/fv87-6bcr

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