The _ c -puzzle solved by means of quark model predictions

The observation of five _c = ssc states by LHCb [Aaij et al. Phys. Rev. Lett. 118 , 182001 ( 2017 )] and the confirmation of four of them by Belle [Yelton et al. Phys. Rev. D 97 , 051102 ( 2018 )], may represent an important milestone in our understanding of the quark organization inside hadrons. By providing results for the spectrum of _ c baryons and predictions for their _ c^+K^- and _ c'^+K^- decay amplitudes within an harmonic oscillator based model, we suggest a possible solution to the _c quantum number puzzle and we extend our mass and decay width predictions to the _b states. Finally, we discuss why the set of _ c(b) baryons is the most suitable environment to test the validity of three-quark and quark–diquark effective degrees of freedom.