QCD sum rules for the determination of form factors of Λ b and Λ c semileptonic decays are investigated. With a form for the baryonic current appropriate for the limits of the heavy quark symmetries, the different tensor structures occurring in the two-and three-point functions are separately studied, and in each case general relations are written for the form factors. Particular attention is given to the treatment of the kinematical region ascribed to the continuum. The t-dependence of the form factors and the decay rates are numerically evaluated and compared to experimental information.

The recently extracted matter radius of carbon isotope 22 C allows us to estimate the mean-square distance of a halo neutron with respect to the center-of-mass of this nucleus. By considering this information, we suggest an energy region for an experimental investigation of the unbound 21 C virtual state. Our analysis, in a renormalized zero-ranged three-body model, also indicates that the two-neutron separation energy in 22 C is expected to be found below ∼0.4 MeV, where the 22 C is approximated by a Borromean configuration with a pointlike 20 C and two s-wave halo neutrons. A virtual-state energy of 21 C close to zero, would make the 22 C, within Borromean nuclei configurations, the most promising candidate to present an excited bound Efimov state or a continuum three-body resonance. PACS 27.30.+t,21.10.Gv, 21.45.+v,11.80.Jy, 21.10.Dr

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The study of charmonium dissociation in heavy ion collisions is generally performed in the framework of effective Lagrangians with meson exchange. Some studies are also developed with the intention of calculate form factors and coupling constants related with charmed and light mesons. These quantities are important in the evaluation of charmonium cross sections. In this paper we present a calculation of the ωDD vertex that is a possible interaction vertex in some meson-exchange models spread in the literature. We used the standard method of QCD Sum Rules in order to obtain the vertex form factor as a function of the transferred momentum. Our results are compatible with the value of this vertex form factor (at zero momentum transfer) obtained in the vector-meson dominance model.

The J/ψ π →D D * , DD * ,D * D * andD D cross sections as a function of √ s are evaluated in a QCD sum rule calculation. We study the Borel sum rule for the four point function involving pseudoscalar and vector meson currents, up to dimension four in the operator product expansion. We find that our results are smaller than the J/ψ π → charmed mesons cross sections obtained with models based on meson exchange, but are close to those obtained with quark exchange models.