Abstract
In this letter, we decode the newly observed charmoniumlike states, Y(4320) and Y(4390), by introducing interference effect between psi (4160) and psi (4415), which plays a role of resonance killer for Y(4320) and Y(4390). It means that two newly reported charmoniumlike states are not genuine resonances, according to which we can naturally explain why two well-established charmonia psi (4160) and psi (4415) are missing in the cross sections of e^+e^- rightarrow pi ^+ pi ^- J/psi and pi ^+ pi ^- h_c simultaneously. To well describe the detailed data of these cross sections around sqrt{s}=4.2 GeV, our study further illustrates that a charmoniumlike structure Y(4220) must be introduced. As a charmonium, Y(4220) should dominantly decay into its open-charm channel e^+e^- rightarrow D^0 pi ^+ D^{*-}, which provides an extra support to psi (4S) assignment to Y(4220). In fact, this interference effect introduced to explain Y(4320) and Y(4390) gives a typical example of non-resonant explanations to the observed XYZ states, which should be paid more attention especially before identifying the observed XYZ states as genuine resonances.
Highlights
The study on charmoniumlike X Y Z states has become a hot issue of hadron physics
The above analysis indicates that the asymmetric broad structure appearing in the π +π − J/ψ invariant mass spectrum is due to the interference effect between two charmonia ψ(4160) and ψ(4415), a charmoniumlike Y state and the background
What is more important is that our study presented in this letter illustrates the interference effect plays a role of a resonance killer for newly observed charmoniumlike states Y (4320) and Y (4390)
Summary
(2) With the observation of three vector Y states, we notice a puzzling phenomenon, i.e., two well established charmonia ψ(4160) and ψ(4415) simultaneously disappear from experimental data of cross sections for the e+e− → π +π − J/ψ [8] and e+e− → π +π −hc [9] processes. When checking the BESIII data of the cross section for the e+e− → π +π − J/ψ process [8], we notice the appearance of a broad structure around 4.2 GeV, and the simultaneous absence of two charmonia ψ(4160) and ψ(4415).
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