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Register a new userY(4260) --> gamma + X(3872) in the diquarkonium picture
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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.
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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 $Y(4260)$ 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 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.
We report on some ideas concerning the nature of the X(3872) resonance and the need for approximately equal charged and neutral components of $D bar{D}^* +cc$. Then we discuss how some hidden charm states are obtained from the interaction between vector mesons with charm and can be associated to some of the charmonium-like X,Y,Z states. Finally we discuss how the nature of these states could be investigated through different types of radiative decay.
New measurements on cross sections in $e^+e^-to J/psipi^+pi^-$, $h_cpi^+pi^-$, $D^0D^{*-}pi^++c.c.$, $psi(2S)pi^+pi^-$, $omegachi_{c0}$ and $J/psieta$ channels have been carried out by BESIII, Belle and BABAR collaborations, and also in the $D_s^*bar D_s^*$ channel. We perform extensive numerical analyses by combining all these data available, together with those in $Dbar D^*$ and $D^*bar D^*$ channels. Though the latter show no evident peak around $sqrt{s}=4.230$ GeV, the missing $X(4260)$ is explained as that it is concealed by the interference effects of the well established charmonia $psi(4040)$, $psi(4160)$ and $psi(4415)$. Our analyses reveal that the leptonic decay width of $X(4260)$ ranges from $O(10^2)$ eV to $O(1)$ keV, and hence may be explained in the conventional quark model picture. That is, the $X(4260)$ may well be interpreted as a mixture of $4^3S_1$ and $3^3D_1$ states.
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