Nonrelativistic treatment of fully-heavy tetraquarks as diquark-antidiquark states

Abstract

The goal of the present work is to obtain a reliable estimate of the masses of the ground and radially excited states of fully-heavy tetraquark systems. In order to do this, we use a nonrelativistic model of tetraquarks which are assumed to be compact and consist of diquark-antidiquark pairs. This nonrelativistic model is composed of Hulthen potential, a linear confining potential and spin-spin interaction. We computed ground, first, and second radially excited $$cc{\bar{c}}{\bar{c}}$$ c c c ¯ c ¯ and $$bb{\bar{b}}{\bar{b}}$$ b b b ¯ b ¯ tetraquark masses. It was found that predicted masses of ground states of $$cc{\bar{c}}{\bar{c}}$$ c c c ¯ c ¯ and $$bb{\bar{b}}{\bar{b}}$$ b b b ¯ b ¯ tetraquarks are significantly higher than the thresholds of the fall-apart decays to the lowest allowed two-meson states. These states should be broad and are thus difficult to observe experimentally. First radially excited states are considerably lower than their corresponding (2S-2S) two-meson thresholds. We hope that our study may be helpful to the experimental search for ground and excited $$cc{\bar{c}}{\bar{c}}$$ c c c ¯ c ¯ and $$bb{\bar{b}}{\bar{b}}$$ b b b ¯ b ¯ tetraquark states.

An updated review of the new hadron states

“…See also theoretical studies of Refs. [608,609,610] using various constituent quark models. Besides, the X(6900) was interpreted in Refs.…”

The $X(6900)$ peak could be a molecular state

“…Considering that the tetra-quark idea is rather attractive in the literature (see for example, refs. [11], [12], [18], [19], [30] ), it is important to make a more careful re-analysis on the nature of X(6900). The present analysis points out that, there still exists the possibility that the X(6900) state be a molecular state composed of particles which thresholds are closer to X(6900) comparing with J/ψψ(3686), such as J/ψψ(3770), J/ψψ 2 (3823), J/ψψ 3 (3842) and χ c0 χ c2 , etc.…”

X(6200) as a compact tetraquark in the QCD string model

“…[56]. The second subgroup, which is basically as populated as the first one, predicts a relatively heavy tetraquark at approximately 6.4-6.5 GeV [3,6,10,22,24,25,28,41,46,57,58]. These calculations received an additional attention of the community after the LHCb result on the double-J/ψ spectrum was announced since they were supposed to explain the enhancement at 6.9 GeV claimed by LHCb.…”