Hunting for states in the recent LHCb di-$J/ψ$ invariant mass spectrum

Abstract

Partial wave analysis is performed, with effective potentials as dynamical inputs, to scrutinize the recent LHCb data on the di-J/ψ invariant mass spectrum. Coupled-channel effects are incorporated in the production amplitude via final state interactions. The LHCb data can be well described. A dynamical generated pole structure, which can be identified as the X(6900) state, is found. Our analysis also provides hints for the existence of three other possible states: a bound state X(6200), a broad resonant state X(6680) and a narrow resonant state X(7200). The J P C quantum numbers of the X(6680) and X(6900) states should be 2 ++ , while the X(6200) and X(7200) states prefer 0 ++ . To determine the above states more precisely, more experimental data for the channels, such as J/ψψ(2S), J/ψψ(3770), di-ψ(2S), are required.

Is the existence of a $J/ψJ/ψ$ bound state plausible?

“…Meanwhile, one should keep in mind that the line shape of a resonance may deviate from the Breit-Wigner parametrisation significantly if it is located near the threshold of another channel that it can couple with. Several works have investigated the impacts of such threshold effects on the pole location of the X(6900) [39][40][41][42].…”

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

“…This finding was independently confirmed later in Ref. [50]. The corresponding physical state was named X(6200) and its possible quantum numbers were fixed to be 0 ++ or 2 ++ .…”

Hunting for tetraquarks in ultra-pheripheral heavy ion collisions

“…One such possibility is the recent observation by LHCb of a narrow resonance in the di-J/ψ mass spectrum [5], dubbed X(6900) and compatible with a cccc structure. The possibility of such a state was already anticipated by several studies, and later further investigated (see, e.g., [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]). Crucially, no single light hadron can mediate the interaction between charmonia to generate a loosely bound molecule [25,26].…”