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Register a new userStudy of B0-->J/Psi D(*) and etac D(*) in Perturbative QCD
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Motivated by recent interest in soft $J/Psi$ production in B decays, we investigate ${B}^0 to J/Psi D^{(star)}$ and $eta_c D^{(star)}$ decays in perturbative QCD. We find that, within that framework, these decays are calculable since the heavy $cbar{c}$ pair in the final states is created by a hard gluon. The branching ratios are estimated to be around $10^{-7}sim 10^{-8}$, too small to be consistent with the data, suggesting that other mechanism(s) contribute to the observed excess of soft $J/Psi$ in ${B}^0 to J/Psi + X$ decays. The possibility of the production of a hybrid $s{bar d}g$ meson with mass about 2 GeV is briefly entertained.
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The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD approach. It is found that form factors and branching ratios are sensitive to the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of the charmonium wave functions for Coulomb potential and harmonic oscillator potential, respectively, f_J/psi and f_etac are the decay constants of the J/psi and etac mesons, respectively. The large branching ratios and the clear signals of the final states make the Bc --> J/psi pi, etac pi decays to be the prospective channels for measurements at the hadron colliders
The $W$-exchange process $B_{s}$ ${to}$ ${eta}_{c}(J/{psi})D$ is studied with the perturbative QCD approach. Three kinds of wave functions for $B_{s}$ meson and two forms of wave functions for charmonium are considered. It is estimated that branching ratios for $B_{s}$ ${to}$ ${eta}_{c}bar{D}$, ${eta}_{c}D$, $J/{psi}bar{D}$, $J/{psi}D$ decays are the order of $10^{-7}$, $10^{-8}$, $10^{-8}$, $10^{-9}$, respectively, where the largest uncertainty is from wave functions. There is a possibility for measuring these decay in the near future.
We calculated the strong form factor and coupling constant for the $J/psi D^* D^*$ vertex in a QCD sum rule calculation. We performed a double Borel sum rule for the three point correlation function of vertex considering both $J/psi$ and $D^*$ mesons off--shell. The form factors obtained are very different, but they give the same coupling constant.
In two recent reactions by Belle producing $Dbar D$ and $Dbar D^*$ meson pairs, peaks above threshold have been measured in the differential cross sections, possibly indicating new resonances in these channels. We want to study such reactions from the point of view that the $D$ meson pairs are produced from already known or predicted resonances below threshold. Our study shows that the peak in the $Dbar D^*$ production is not likely to be caused by the X(3872) resonance, but the peak seen in $Dbar D$ invariant mass can be well described if the $Dbar D$ pair comes from the already predicted scalar X(3700) resonance.
We analyze two recent reactions of Belle, producing $Dbar D$ and $Dbar D^*$ states that have an enhancement of the invariant $Dbar D$, $Dbar D^*$ mass distribution close to threshold, from the point of view that they might be indicative of the existence of a hidden charm scalar and an axial vector meson states below $Dbar D$ or $Dbar D^*$ thresholds, respectively. We conclude that the data is compatible with the existing prediction of a hidden charm scalar meson with mass around 3700 MeV, though other possibilities cannot be discarded. The peak seen in the $Dbar D^*$ spectrum above threshold is, however, unlikely to be due to a threshold enhancement produced by the presence, below threshold, of the hidden charm axial vector meson X(3872).
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