| The ordinary Ds family can be understood in the cs quark structure. The recentlyobserved new member of the charm-strange family Ds(2632), which has a surprisinglynarrow width, is seriously challenging the usual theory. Some authors propose the fourquark state to interpret the recently observed Ds(2632). Although they have predicted anintuitive picture, they do not account for any concrete dynamics. As the dynamics is notinvolved, their interpretations are not quite satisfying.The method of QCD sum rules, developed more than twenty years ago by Shifman,Vainshtein and Zakharov (SVZ) has become a widely used working tool in hadronsphenomenology. The advantages of this method are well known. Instead of amodel-dependent treatment in terms of constituent quarks, hadrons are represented bytheir interpolating quark currents. The correlation of these currents is introduced andtreated in the framework of the operator product expansion (OPE), where the short- andlong-distance quark-gluon interactions are separated. The former are calculated usingQCD perturbation theory, whereas the latter are parameterized in terms of universalvacuum condensates. The result of the QCD calculation is then matched, via dispersionrelation, to a sum over hadronic states. Numerous properties of hadrons with variousflavor content have been calculated by the sum rule method. The results areencouraging and in most cases reveal a remarkable agreement with experimental data.Therefore, whenever one needs to determine an unknown hadronic parameter, the QCDsum rule prediction is a reliable one. We expect to extract the mass of Ds(2632) fromthe mass sum rule obtained in above way.In this article, we take the point of view that Ds(2632) is a diquark-antidiquark state,and derive the QCD sum rule for interpolating current composed of scalar-scalar type.We find that the value for mass of Ds(2632) is consistent with existing experimentaldata, pointing in favor of the four-quark structure for Ds(2632). |
