Interpretations for the X(4160) observed in the double charm production at B factories

Abstract

Belle Collaboration has recently observed a new state, the X(4160), in the process of double charm production $e^{+}{e}^{-}\to J/\psi +X(4160)$ followed by $X(4160)\to D^{\ast }\overline{D^{\ast }}$. We discuss possible interpretations for the X(4160) based on the NRQCD calculations and the potential model estimates for the charmonium spectrum. We first focus on the D-wave spin-singlet $2^{-+}$ charmonium ${}^1{D}_2(2D)$, which is estimated to have a small production rate of about 5% of that for $e^{+}{e}^{-}\to J/\psi +{\eta }_c(1S)$, and therefore is incompatible with the observed data for X(4160). We then discuss the possibility that the X(4160) is the known $J^{PC}=1^{--}$ charmonium state $\psi (4160)$, which can be produced via two photon fragmentation, but the production rate is much smaller than observed for $e^{+}{e}^{-}\to J/\psi +X(4160)$. In contrast to above two possibilities, the ${\eta }_c(4S)$ assignment is a likely one, which is supported by the observed relatively large production rate and non-observation of $D\bar{D}$ decay of X(4160), but we have to understand why ${\eta }_c(4S)$ has such a low mass, which deserves further studies. The P-wave excited state ${\chi }_{c0}(3P)$ is also an interesting candidate, if the observed broad peak around 3.8-3.9 GeV in the recoil mass of $D\bar{D}$ against $J/\psi$ in $e^{+}+e^{-}\to J/\psi +D\bar{D}$ is due to the ${\chi }_{c0}(2P)$ state. Measurements of production angular distributions will be helpful to distinguish between ${\eta }_c(4S)$ and ${\chi }_{c0}(3P)$ assignments. Production mechanisms in nonrelativistic QCD are emphasized.

arXiv commentversion to appear in Phys. Lette. B, discussions and references added

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• The hidden-charm pentaquark and tetraquark states
• The $XYZ$ states: experimental and theoretical status and perspectives
• Multiquark Resonances
• Non-Standard Heavy Mesons and Baryons, an Experimental Review
• New Charmonium States in QCD Sum Rules: a Concise Review
• Higher Charmonia and X,Y,Z states with Screened Potential
• An overview of $XYZ$ new particles
• Where is the χ_{c0}(2P)?
• A New Hadron Spectroscopy
• Is the X(3915) the chi_{c0}(2P)?
• The $\mathbf{S}-\mathbf{D}$ mixing and di-electron widths of higher charmonium $1^{--}$ states
• Detecting the long-distance structure of the X(3872)
• Dielectron widths of the S-, D-vector bottomonium states
• Analysis of the hidden-charm tetraquark mass spectrum with the QCD sum rules
• Mass spectra for $qc\bar{q}\bar{c}$, $sc\bar{s}\bar{c}$, $qb\bar{q}\bar{b}$, $sb\bar{s}\bar{b}$ tetraquark states with $J^{PC}=0^{++}$ and $2^{++}$
• Are the $X$(4160) and $X$(3915) charmonium states?
• Charmonium states in QCD-inspired quark potential model using Gaussian expansion method
• Search for $C=+$ charmonium and bottomonium states in $e^{+}{e}^{-}\to \gamma +X$ at B factories
• Comprehending heavy charmonia and their decays by hadron loop effects
• Two-Body Strong Decay of the 2P and 3P Charmonium states
• The Strong Decays of X(3940) and X(4160)
• Charmonium states in a coupled-channel model
• Charmonium spectrum with a Dirac potential model in the momentum space
• $P$-wave charmonium contribution to hidden-charm states from reanalysis of lattice QCD data
• Charmonium: Conventional and $XYZ$ States in a Relativistic Screened Potential Model
• The Exclusive Decay of Upsilon into $h_c$, the $X(3940)$ and $X(4160)$
• Analysis of the radiative decays among the charmonium states
• $B_u$ $\to$ $\psi M$ decays and $S$-$D$ wave mixing effects
• Is the $3S$-$2D$ mixing strong for the charmonia $\psi (4040)$ and $\psi (4160)$?
• Hidden and open charm at Belle (and elsewhere)
• Medium modifications of $1P$-wave charmonia ${\chi }_{cJ}(1P)$ in cold nuclear matter
• $X(3860)$ production in association with $J/\psi$ via $e^{+}{e}^{-}$ annihilation at Belle
• Spectroscopy and Decay Properties of Excited Charmonium States