Tests of the nature and of the gluon content of the \sigma(0.6) from D and D_{s} semileptonic decays

Abstract

We summarize the different features which show that QCD spectral sum rule analyses of the scalar two- and three-point functions do not favour the $\bar{u}u+\bar{d}d$ interpretation of the broad and low mass $\sigma (0.6)$ and emphasize that a measurement of the $D_s$ semileptonic decays into $\pi \pi$ can reveal in a model-independent way its eventual gluon component ${\sigma }_B$. The analysis also implies that one expects an observation of the $K\bar{K}$ final states from the ${\sigma }_B$ which may compete (if phase space allowed) with the one from a low mass $\bar{s}s$ state assumed in the literature to be the SU(3) partner of the observed $\sigma (0.6)$ if the latter is a $\bar{u}u+\bar{d}d$ state

Comments: 6 pages latex file. 4 fig.eps