Speaker
Description
The $\Lambda(1670)$ plays an important role in the chiral dynamics of meson-baryon interaction. In the chiral unitary approach, it is dynamically generated from the interaction of the SU(3) octets of pseudoscalar mesons and baryons. The $\Lambda(1670)$ is related to the $\Lambda(1405)$, as both resonances originate from the same coupled-channel meson-baryon dynamics. However, the nature of the $\Lambda(1670)$ remains an open issue.
To gain further insight into its nature, we theoretically study the $\psi(3686) \to \Lambda \bar \Lambda \eta$ reaction [1], where a neat peak for the excitation of the $\Lambda(1670)$ and $\bar \Lambda(1670)$ in the $\eta \Lambda$ and $\eta \bar \Lambda$ invariant mass distributions, respectively, is observed by the BESIII experiment [2]. Our approach uses the fact that the $\psi(3686)$, a $c\bar c$ state, is an SU(3) singlet with respect to the light quarks. We construct the two flavor structures allowed for a pseudoscalar meson, a baryon, and an antibaryon. The resonance signals come from the meson-baryon final-state interaction, which dynamically generates the $\Lambda(1670)$ in our approach. With a reasonable relative weight of the two flavor structures, the only free parameter of the model, we obtain the three mass distributions in good agreement with experiment, giving extra support to the molecular structure of the $ \Lambda(1670)$ resonance. The agreement with the data is further improved by including an additional resonance contribution with a mass around 2200 MeV.
This presentation is based on our recent work [1].
[1] N. Ikeno and E. Oset, arXiv:2606.10578 [hep-ph].
[2] M. Ablikim et al. (BESIII), Phys. Rev. D 106, 072006 (2022).