Over the past two decades, several heavy-flavor hadrons have been observed, with their properties inconsistent with predictions from conventional $q\bar{q}$
or $qqq$ models. These findings offer insights into quark binding and QCD. It is then important to continue the search for new states, as each discovery improves our knowledge and provides important input to the theory.
This talk presents an amplitude analysis of the $B^0\to \eta_c(1S)K^+\pi^-$ decay, based on a dataset corresponding to approximately 9 fb$^{-1}$ of proton-proton collision data. The analysis search for the presence of an exotic resonance in the $\eta_c(1S)\pi^-$ system.
The Dalitz plot is described using only established $K^*$ resonances as intermediate states, as no significant evidence is found for an exotic resonance, contrary to an earlier claim based on previous data.
The inclusive branching fraction of the decay is measured together with the branching fracions of the $B^0\to \eta_c(1S)K^*$ decays.