No Arabic abstract
Recently, a new structure $Y(4626)$ was reported by the Belle Colloboration in the process $e^+e^-to D_s^+D_{s1}(2536)^-$. In this work, we propose an assignment of the $Y(4626)$ as a ${D}^*_sbar{D}_{s1}(2536)$ molecular state, which decays into the $D_s^+D_{s1}(2536)^-$ channel through a coupling between ${D}^*_sbar{D}_{s1}(2536)$ and ${D}_sbar{D}_{s1}(2536)$ channels. With the help of the heavy quark symmetry, the potential of the interaction ${D}^*_sbar{D}_{s1}(2536)-{D}_sbar{D}_{s1}(2536)$ is constructed within the one-boson-exchange model, and inserted into the quasipotential Bethe-Salpeter equation. The pole of obtained scattering amplitude is searched for in the complex plane, which corresponds to a molecular state from the interaction ${D}^*_sbar{D}_{s1}(2536)-{D}_sbar{D}_{s1}(2536)$. The results suggest that a pole is produced near the ${D}^*_sbar{D}_{s1}(2536)$ threshold, which exhibits as a peak in the invariant mass spectrum of the ${D}_sbar{D}_{s1}(2536)$ channel at about 4626 MeV. It obviously favors the $Y(4265)$ as a ${D}^*_sbar{D}_{s1}(2536)$ molecular state. In the same model, other molecular states from the interaction ${D}^*_sbar{D}_{s1}(2536)-{D}_sbar{D}_{s1}(2536)$ are also predicted, which can be checked in future experiments.
Recently a vector charmonium-like state $Y(4626)$ was observed in the portal of $D^+_sD_{s1}(2536)^-$. It intrigues an active discussion on the structure of the resonance because it has obvious significance for gaining a better understanding on its hadronic structure with suitable inner constituents. It indeed concerns the general theoretical framework about possible structures of exotic states. Since the mass of $Y(4626)$ is slightly above the production threshold of $D^+_sbar D_{s1}(2536)^-$ whereas below that of $D^*_sbar D_{s1}(2536)$ with the same quark contents as that of $D^+_sbar D_{s1}(2536)^-$, it is natural to conjecture $Y(4626)$ to be a molecular state of $D^{*}_sbar D_{s1}(2536)$, as suggested in literature. Confirming or negating this allegation would shed light on the goal we concern. We calculate the mass spectrum of a system composed of a vector meson and an axial vector i.e. $D^*_sbar D_{s1}(2536)$ within the framework of the Bethe-Salpeter equations. Our numerical results show that the dimensionless parameter $lambda$ in the form factor which is phenomenologically introduced to every vertex, is far beyond the reasonable range for inducing an even very small binding energy $Delta E$. It implies that the $D^*_sbar D_{s1}(2536)$ system cannot exist in the nature as a hadronic molecule in this model, so that we may not think the resonance $Y(4626)$ to be a bound state of $D^*_sbar D_{s1}(2536)$, but something else, for example a tetraquark and etc.
Using a data sample of 921.9 fb$^{-1}$ collected with the Belle detector, we study the process of $e^+e^-to D^+_sD_{s1}(2536)^-+c.c.$ via initial-state radiation. We report the first observation of a vector charmoniumlike state decaying to $D^+_sD_{s1}(2536)^-+c.c.$ with a significance of 5.9$sigma$, including the systematic uncertainties. The measured mass and width are $(4625.9^{+6.2}_{-6.0}({rm stat.})pm0.4({rm syst.}))~{rm MeV}/c^{2}$ and $(49.8^{+13.9}_{-11.5}({rm stat.})pm4.0({rm syst.}))~{rm MeV}$, respectively. The product of the $e^+e^-to D^+_sD_{s1}(2536)^-+c.c.$ cross section and the branching fraction of $D_{s1}(2536)^-to{bar D}^{*0}K^-$ is measured from the $D_s bar{D}_{s1}(2536)$ threshold to 5.59~GeV.
Very recently it was predicted the existence of a charged state near the $D_sbar{D}^*/D^*_sbar{D}$ threshold. This state, that we call $Z_{cs}^+$, would be the strange partner of the recently observed $Z_c^pm(3900)$. Using standard techniques of QCD sum rules, we evaluate the three-point function for the vertices $Z_{cs}^+ , J/psi , K^+$, $Z_{cs}^+ , eta_c , K^{*+}$ and $Z_{cs}^+ , D_s^+bar{D}^{*0}$ and we make predictions for the corresponding decay widths in these channels.
In the present work, we construct the color-singlet-color-singlet type four-quark currents to investigate the $D_sbar{D}_{s1}$ and $D_s^*bar{D}_{s0}^*$ tetraquark molecular states with the $J^{PC}=1^{--}$ and $1^{-+}$ via the QCD sum rules, and obtain satisfactory results. We can search for the $D_sbar{D}_{s1}$ and $D_s^*bar{D}_{s0}^*$ tetraquark molecular states with the $J^{PC}=1^{--}$ and $1^{-+}$ at the BESIII and Belle II in the future.
We report a study of the decays B -> D_s1(2536)+ anti-D(*), where anti-D(*) is anti-D0, D- or D*-, using a sample of 657 x 10^6 B anti-B pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The branching fractions of the decays B+ -> D_s1(2536)+ anti-D0, B0 -> D_s1(2536)+ D- and B0 -> D_s1(2536)+ D*- multiplied by that of D_s1(2536)+ -> (D*0K+ + D*+K0) are found to be (3.97+-0.85+-0.56) x 10^-4, (2.75+-0.62+-0.36) x 10^-4 and (5.01+-1.21+-0.70) x 10^-4, respectively.