Tetraquarks with hidden charm and strangeness as φ-ψ(2S) hadrocharmonium

Abstract

In the hadrocharmonium picture a c̄c state and a light hadron form a bound state. The effective interaction is described in terms of the chromoelectric polarizability of the c̄c state and energy-momentum-tensor densities of the light hadron. This picture is justified in the heavy quark limit, and may successfully account for a hidden-charm pentaquark state recently observed by the LHCb Collaboration. In this work we extend the formalism to the description of hidden-charm tetraquarks, and address the question of whether the resonant states observed by LHCb in the J/ψ-φ spectrum can be described as hadrocharmonia. This is a nontrivial question because nothing is known about the φ meson energy-momentum-tensor densities. With rather general assumptions about energy-momentum-tensor densities in the φ meson we show that a ψ(2S)-φ bound state can exist, and we obtain a characteristic relation between its mass and width. We show that the tetraquark X(4274) observed by LHCb in the J/ψ-φ spectrum is a good candidate for a hadrocharmonium. We make predictions which will allow testing this picture. Our method can be generalized to identify other potential hadrocharmonia.