Strangeness is the key: from $\bar{K}N$ to $\bar{D}_s D K$

Abstract

The kaon, the lightest hadron containing a strangeness quark, is very peculiar. It is a Nambu-Goldstone boson, but significantly heavier than the pion. As a result, its interaction with a matter particle, such as the nucleon or a heavy-light meson, such as the $D$ meson, is completely determined by chiral dynamics and much stronger than its pion cousin. The strong attractive interaction has brought us many surprises and is manifested in the peculiar nature of many particles, such as the mysterious $Λ(1405)$ and $D_{s0}^*(2317)$. These two particles can be understood as $\bar{K}N$ and $DK$ hadronic molecules, respectively. They also imply the existence of three-body hadronic molecules that await future discovery. In this talk, I review some recent developments in our understanding of hadronic interactions involving the kaon.

Figures (4)

• Figure 1: Discovery timeline of selected exotic hadrons. The color code denotes their classification: "exotic baryons and mesons" denote that they have quantum numbers of CQM hadrons, but have peculiar properties; "tetraquarks" denote mesons that have a minimum of four constituent quarks/antiquarks; "pentaquarks" denote baryons that contain at least five constituent quarks.
• Figure 2: Trajectories of the two poles of $\Lambda(1405)$ as functions of the pion mass $m_{\pi}$ from 137 MeV to 497 MeV. Critical masses are labeled by solid squares, with points equally spaced between them. Taken from Ref. Xie:2023cej.
• Figure 3: RMS radii of subsystems in the $D\bar{D}K$ (left), $D\bar{D}^*K$ (middle), and $DDK$Wu:2019vsy bound states with a cutoff $R_c=1.0$ fm. Taken from Ref. Wu:2020job.
• Figure 4: The predicted masses of $0^{--}$$\bar{D}_s DK$ three-body molecular state and $0^{-+}$$\bar{D}_s DK$ three-body molecular state compared with the $0^{-+}$$\bar{D}_sD_{s0}^*$ molecular state and their thresholds. Taken from Ref. Wu:2025fzx.