Abstract

The charmoniumlike state $Y(4260)$ is described as predominantly a $D_1 \bar{D}$ molecule in a coupled-channel quark model [Phys.\,Rev.\,D\,\textbf{96},\,114022\,(2017)]. The heavy quark spin symmetry (HQSS) thus implies the possible emergence of its heavy quark spin partners with molecular configuration as $D_1 \bar{D}^*$ and $D_2^* \bar{D}^*$ below these charmed mesons' thresholds. We analyze the probabilities of various intermediate charmed meson loops for $J^{PC}=1^{--}$ exotic state $Y(4360)$ and find that the channel $D_1 \bar{D}^*$ couples more strongly around its mass regime, and the coupling behavior remains the same even if the mass of $Y(4360)$ is pushed closer to $D_1 \bar{D}^*$ threshold. This enlightens that the most favorable molecular scenario for the $Y(4360)$ could be $D_1 \bar{D}^*$, and hence it can be interpreted as HQSS partner of the $Y(4260)$. We also find the strong coupling behavior of $D_2^* \bar{D}^*$ channel with the $\psi(4415)$, which makes it a good candidate for a dominant $D_2^* \bar{D}^*$ molecule. We discuss the important decay patterns of these resonances to disentangle their long- and short-distance structures.

Highlights

  • We analyze the probabilities of various intermediate charmed meson loops for JPC 1⁄4 1−− exotic state Yð4360Þ and find that the channel D1D Ã couples more strongly around its mass regime, and the coupling behavior remains the same even if the mass of Yð4360Þ is pushed closer to D1D Ã threshold

  • Heavy quark spin symmetry (HQSS) implies that the hadronic interactions do not depend on the spin of the heavy quark, and heavy mesons can be fully classified by using the quantum numbers of the light quark cloud

  • As Yð4260Þ is dominant by the D1Dmolecular component, its heavy quark spin symmetry (HQSS) partners D1D Ã and DÃ2D Ã naturally emerge and we identify them as the JPC 1⁄4 1−− charmoniumlike state Yð4360Þ and ψð4415Þ, respectively

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Summary

INTRODUCTION

Heavy quark spin symmetry (HQSS) implies that the hadronic interactions do not depend on the spin of the heavy quark, and heavy mesons can be fully classified by using the quantum numbers of the light quark cloud. Before we go into details of our calculations, we first briefly review the status of Yð4360Þ This charmoniumlike structure was first observed in 2007 at BABAR in the initial state radiation (ISR) process eþe− → πþπ−ψð2SÞ [16], and later, in the same year at Belle [17]. Yð4360Þ is recognized as a potential candidate for an exotic state since it does not show strong coupling to opencharm channels (such as DD ) which are generally expected as dominant decays of vector charmonia.

COUPLED-CHANNEL FORMALISM
Coupling Strengths for Yð4360Þ
REMARKS ON DECAYS
SUMMARY
1.45 GeV mc ms
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