Relatore
Descrizione
The $Z_{cs}$(3985) state was reported as a new exotic state by BESIII collaboration. After its discovery, the $Z_{cs}$(4000) and $Z_{cs}$(4220) states were observed at LHCb. We study the $Z_{cs}$(3985) state based on the $\bar D_s D^*$ with the coupled channels of the vector-pseudoscalar mesons [1]. We find that we can explain this state by the threshold effect from the coupled-channel interaction and our calculation is in fair agreement with the BESIII data. We also study the $Z_{cs}$ state based on $D^*_s \bar D^*$ with the coupled channels of the vector-vector mesons [2]. The $D^*_s \bar D^*$ system does not develop a bound state, however, the $J^P = 2^+$ channel has enough attraction to create a strong cusp structure that shows up in the $J/\psi K^+$ invariant mass distribution in the $B^+ \to J/\psi \phi K^+$ decay at the $D^*_s \bar D^*$ threshold. I will give a presentation based on Refs. [1]-[2].
[1] N. Ikeno, R. Molina and E. Oset, Phys. Lett. B 814, 136120 (2021).
[2] N. Ikeno, R. Molina and E. Oset, Phys. Rev. D 105, 014012 (2022).
