Exploring fully heavy scalar tetraquarks Q Q Q Q

The masses, current couplings and widths of the fully heavy scalar tetraquarks X4Q = Q Q Q Q, Q = c, b are calculated by modeling them as four-quark systems composed of axial-vector diquark and antidiquark. The masses m(') and couplings f (') of these tetraquarks are computed in the context of the QCD sum rule method by taking into account a nonperturbative term proportional to the gluon condensate (& alpha;sG2/& pi;). Results m = (6570 & PLUSMN; 55) MeV and m' = (18540 & PLUSMN; 50) MeV are used to fix kinematically allowed hidden-flavor decay channels of these states. It turns out that, the processes X4c & RARR; J/& psi; J/& psi;, X4c & RARR; & eta;c & eta;c, and X4c & RARR; & eta;c & chi;c1(1P) are possible decay modes of X4c. The partial widths of these channels are evaluated by means of the couplings gi, i = 1, 2, 3 which describe strong interactions of tetraquark X4c and mesons at relevant vertices. The couplings gi are extracted from the QCD threepoint sum rules by extrapolating corresponding form factors gi(Q 2) to the mass-shell of a final meson. The mass of the scalar tetraquark X4b is below the & eta;b & eta;b and ϒ(1S)ϒ(1S) thresholds, therefore it does not fall apart to these bottomonia, but transforms to conventional particles through other mechanisms. Comparing m = (6570 & PLUSMN; 55) MeV and 4c = (110 & PLUSMN; 21) MeV with parameters of structures observed by the LHCb, ATLAS and CMS collaborations, we interpret X4c as the resonance X(6600) reported by CMS. Comparisons are made with other theoretical predictions.& COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/). Funded by SCOAP3.