Structural dissection of hadronic molecules: The $D^{(*)}\bar{K}^{(*)}$ family under QCD light-cone sum rules

TL;DR

This paper calculates electromagnetic properties of charm-strange molecular tetraquarks using QCD light-cone sum rules, providing insights into their structure and aiding experimental identification.

Contribution

It extends QCD light-cone sum-rule analysis to systematically determine electromagnetic moments of $D^{(*)}ar{K}^{(*)}$ molecular systems, offering benchmarks for distinguishing molecular states.

Findings

Magnetic moments range from 1 to 3 nuclear magnetons.

Quadrupole moments are about $10^{-3} ext{ fm}^2$, indicating near-spherical charge distributions.

Magnetic response is dominated by light quarks, charm contribution is suppressed.

Abstract

We investigate the static electromagnetic properties of three charm--strange molecular tetraquark candidates with quantum numbers $J^{P}=1^{+}$, namely the $D\bar{K}^{\ast}$, $D^{\ast}\bar{K}$, and $D^{\ast}\bar{K}^{\ast}$ systems. The analysis is carried out within the framework of QCD light-cone sum rules, using interpolating currents constructed from colour-singlet meson bilinears to reflect their molecular configurations. Both perturbative and non-perturbative photon contributions are included,and numerical predictions for the magnetic and electric quadrupole moments are obtained. The magnetic moments are found to lie in the range $1$--$3$ nuclear magnetons, with the largest value associated with the $D^{*}\bar{K}$ configuration. The quadrupole moments are an order of magnitude smaller, of order $10^{-3}\,\mathrm{fm}^{2}$, indicating only weak deviations from spherical charge distributions. A flavour decomposition shows that the magnetic response is dominated by the light quarks, while the charm-quark contribution is strongly suppressed, a feature naturally expected for loosely bound hadronic molecules. The present analysis extends QCD light-cone sum-rule studies of exotic hadrons by providing a systematic determination of the electromagnetic moments of the $D^{(\ast)}\bar K^{(\ast)}$ molecular systems. These results provide quantitative benchmarks that may help discriminate between molecular configurations and more compact multiquark interpretations and may offer useful guidance for future experimental studies of electromagnetic signatures of charm--strange exotic states.