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Register a new userLight-quark components analysis and the nature of the $Y(4260)$
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We study the processes $e^+ e^- to Y(4260) to J/psi pipi(Kbar{K})$. The strong final-state interactions, especially the coupled-channel ($pipi$ and $Kbar{K}$) final-state interaction in the $S$-wave are taken into account in a model-independent way using dispersion theory. It is found that the light-quark SU(3) octet state plays a significant role in these transitions, implying that the $Y(4260)$ contains a large light-quark component. Our findings suggest that the $Y(4260)$ is neither a hybrid nor a conventional charmonium state. Furthermore, through an analysis of the ratio of the light-quark SU(3) octet and singlet components, we show that the $Y(4260)$ does not behave like a pure $bar D D_1$ hadronic molecule as well.
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The $Y(4260)$ has been one of the most puzzling pieces among the so-called $XYZ$ states. In this paper, we try to gain insights into the structure of the $Y(4260)$ from the light-quark perspective. We study the dipion invariant mass spectrum of the $e^+ e^- to Y(4260) to J/psi pi^+pi^-$ process and the ratio of the cross sections ${sigma(e^+e^- to J/psi K^+ K^-)}/{sigma(e^+e^- to J/psi pi^+pi^-)}$. In particular, we consider the effects of different light-quark SU(3) eigenstates inside the $Y(4260)$. The strong pion-pion final-state interactions as well as the $Kbar{K}$ coupled channel in the $S$-wave are taken into account in a model-independent way using dispersion theory. We find that the SU(3) octet state plays a significant role in these transitions, implying that the $Y(4260)$ contains a large light-quark component. Our findings suggest that the $Y(4260)$ is neither a hybrid nor a conventional charmonium state, and they are consistent with the $Y(4260)$ having a sizeable $bar D D_1$ component which, however, is not completely dominant.
We report the results of a search for the $B to Y(4260) K, ~Y(4260)to J/psipi^+pi^-$ decays. This study is based on a data sample corresponding to an integrated luminosity of 711~fb$^{-1}$, collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We investigate the $J/psipi^+pi^-$ invariant mass distribution in the range 4.0 to 4.6 GeV/$c^2$ using both $B^+ to J/psi pi^+pi^- K^+$ and $B^0 to J/psi pi^+pi^- K^0_S$ decays. We find excesses of events above the background levels, with a significances of 2.1 and 0.9 standard deviations for charged and neutral $B to Y(4260) K$ decays, respectively, taking into account the systematic uncertainties. These correspond to upper limits on the product of branching fractions, ${cal B}(B^+ to Y(4260) K^+) times {cal B}(Y(4260) to J/psi pi^+ pi^-) <1.4 times 10^{-5}$ and ${cal B}(B^0 to Y(4260) K^0) times {cal B}(Y(4260) to J/psi pi^+ pi^-) <1.7 times 10^{-5}$ at the 90% confidence level.
The observed Y(4260)to gamma + X(3872) decay is a natural consequence of the diquark-antidiquark description of Y and X resonances. In this note we attempt an estimate of the transition rate, Gamma_{rm rad}, by a non-relativistic calculation of the electric dipole term of a diquarkonium bound state. We compute Gamma_{rm rad} for generic composition values of the isospin of X and Y. Specializing to I=0 for X(3872), we find Gamma_{rm rad}= 496~keV for Y(4260) with I=0 and Gamma_{rm rad}= 179~keV for I=1. Combining with BESIII data, we derive upper bounds to B(Yto J/Psi+pi+pi) and to Gamma(Yto mu^+ mu^-). We expect to confront these results with forthcoming data from electron-positron and hadron colliders.
Many vector charmonium-like states have been reported recently in the cross sections of $e^+e^- rightarrow omegachi_{c0}$, $pi^{+}pi^{-}h_c$, $pi^{+}pi^{-}J/psi$, $pi^{+}pi^{-}psi(3686)$ and $pi^{+}D^{0}D^{*-}+c.c.$ To better understand the nature of these states, a combined fit is performed to these cross sections by using three resonances $Y(4220)$, $Y(4390)$ and $Y(4660)$. The resonant parameters for the three resonances are obtained. We emphasize that two resonances $Y(4220)$ and $Y(4390)$ are sufficient to explain these cross sections below 4.6 GeV. The lower limits of $Y(4220)$ and $Y(4390)$s leptonic decay widths are also determined to be $(36.4pm2.0pm4.2)$ and $(123.8pm6.5pm9.0)$ eV.
The mass spectrum and the two-body open-charm decays of the $J^{PC}=1^{--}$ charmonium states are studied with the coupled-channel effects taken into account. The coupled-channel-induced mixing effects among the excited vector charmonia are studied. Based on our calculations of the masses and the decay widths, we find that the tension between the observed properties of $Y(4260)/Y(4360)$ and their conventional charmonia interpretations could be softened.
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