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.
We present the formalism for the decay of dynamically generated scalar mesons with open- or hidden-charm and give results for the decay of D^*_{s0} (2317) to gamma D_s^* plus that of a hidden charm scalar meson state predicted by the theory around 3700 MeV decaying into gamma J/psi.
Many new states in the charmonium mass region were recently discovered by BaBar, Belle, CLEO-c, CDF, D0, BESIII, LHCb and CMS Collaborations. We use the QCD Sum Rule approach to study the possible structure of some of these states.
Starting from a molecular picture for the X(3872) resonance, this state and its J^{PC}=2++ HQSS partner [X2(4012)] are analyzed within a model which incorporates possible mixings with 2P charmonium states. Since it is reasonable to expect the bare ch
i_{c1}(2P) to be located above the Dbar D* threshold, but relatively close to it, the presence of the charmonium state provides an effective attraction that will contribute to bind the X(3872), but it will not appear in the 2++ sector. Indeed in this latter sector, the chi_{c2}(2P) should provide an effective small repulsion, because it is placed well below the D*bar D* threshold. We show how the 1++ and 2++ bare charmonium poles are modified due to the D(*)bar D(*) loop effects, and the first one is moved to the complex plane. The meson loops produce, besides some shifts in the masses of the charmonia, a finite width for the 1++ dressed charmonium state. On the other hand, the X(3872) and X2(4012) start developing some charmonium content, which is estimated by means of the compositeness Weinberg sum-rule. We also show that for X(3872) molecular probabilities of around 70-90 %, the X2 resonance destabilizes and disappears from the spectrum, becoming either a virtual state or being located deep into the complex plane, with decreasing influence in the D* bar D* scattering line.
The challenges with the molecular model of the multiquark systems are the identification of the hadronic molecules and the interaction between two color neutral hadrons. We study the di-hadronic molecular systems with proposed interaction potential a
s s-wave one boson exchange potential along with Screen Yukawa-like potential, and arrived with the proposal that within hadronic molecule the two color neutral hadrons experience the dipole-like interaction. The present study is the continuation of our previous study cite{arxiv-Rathaud-penta}. With the proposed interaction potential, the mass spectra of $Sigma_{s}K^{*}$, $Sigma_{c}K^{*}$, $Sigma_{b}K^{*}$, $Sigma_{s}D^{*}$, $Sigma_{c}D^{*}$, $Sigma_{b}D^{*}$, $Sigma_{s}B^{*}$, $Sigma_{c}B^{*}$, $Sigma_{b}B^{*}$, $Xi_{s}K^{*}$, $Xi_{c}K^{*}$, $Xi_{b}K^{*}$, $Xi_{s}D^{*}$, $Xi_{c}D^{*}$, $Xi_{b}D^{*}$, $Xi_{s}B^{*}$, $Xi_{c}B^{*}$, $Xi_{b}B^{*}$ meson-baryon molecules are predicted. The Weinberg compositeness theorem which provides clue for the compositeness of the state is used for determination of the scattering length and effective range. The present study predict $P_{c}(4450)$ pentaquark sate as $Sigma_{c}D^{*}$ molecule with $I(J^{P})=frac{1}{2}(frac{3}{2}^{-})$. The formalism also predicts some very interesting open as well as hidden flavour near threshold molecular pentaquark states.