Fully charmed resonance X(6900) and its beauty counterpart

Abstract

The fully heavy scalar tetraquarks T4Q=QQQ?Q?, (Q=c,b) are explored in the context of QCD sum rule method. We model T4Q as diquark-antidiquark systems composed of pseudoscalar constituents, and calculate their masses m(?) and couplings f(?) within the two-point sum rule approach. Our results m=(6928±50)MeV and m?=(18858±50)MeV for masses of the tetraquarks T4c and T4b prove that they can decay to hidden-flavor heavy mesons. The full width ?4c of the T4c is evaluated by taking into account the decay channels T4c?J/?J/?, J/???, ?c?c, ?c?c(2S), ?c?c1(1P), and ?c0?c0. The partial widths of these processes depend on strong couplings gi at vertices T4cJ/?J/?, T4cJ/??? etc., which are computed using the QCD three-point sum rule method. The decay T4b??b?b is used to find the width ?4b of the T4b. The predictions for m and ?4c=(128±22)MeV are compared with parameters of the fully charmed resonances reported by the LHCb, ATLAS, and CMS Collaborations. Based on this analysis, we interpret the tetraquark T4c as a candidate to the resonance X(6900). The mass m? and width ?4b=(94±28)MeV of the exotic meson T4b can be used in future experimental investigations of these states. © 2023 Elsevier B.V.