eta nucleus optical potential in a chiral unitary approach

The self-energy of an eta in a nuclear medium is calculated in a chiral unitary model, and applied to eta states in nuclei. Our calculation predicts an attractive eta nucleus optical potential which can accommodate many eta bound states in different nuclei.Comment: 4 pages, 2 figures, Talk given at the XVI International Conference on Particles and Nucle

A critical analysis on deeply bound kaonic states in nuclei

We make a critical analysis on the theoretical calculations that lead to predictions of deeply bound kaonic states in nuclei. The model set-up, after dropping several important processes and channels, leads unavoidably to an unrealistic deep potential with a very small imaginary part. We review also the experimental results taken as reference for the claim of deeply bound kaons. We suggest that the peaks of the proton spectra come from $K^-$ absorption on a pair of nucleons, leaving the rest of the nucleons as spectators. Based on this conjecture we predict what would happen in other nuclei.Comment: 19 pags., 4 figs, version to be published in Phys. Rev.

The (π−,γγ)(\pi^-,\gamma\gamma) reaction in nuclei and the σ\sigma meson in the medium

A theoretical analysis of the $(\pi^-,\gamma\gamma)$ reaction in nuclei is made in order to find the viability of this reaction to test modifications of the $\sigma$ meson mass in nuclear matter. The $\pi\pi$ correlation in the scalar-isoscalar channel in nuclear matter could, in principle, manifest itself in this reaction since it plays an important role in the $\pi\pi\to\gamma\gamma$ mechanism. But we conclude that this effect is hardly visible in this reaction due to the strong background of the pion-Bremsstrahlung terms. Only with some special cuts and for some polarization states are the effect visible at the cost of a strong reduction in the cross section.Comment: 16 pages, 11 figure

The Y(3940), Z(3930) and the X(4160) as dynamically generated resonances from the vector-vector interaction

We study the vector-vector interaction within the framework of the hidden gauge formalism for the sector with quantum numbers charm C=0 and strangeness S=0 in the region around 4000 MeV. We get five poles, three of which could be identified with the Y(3940), Z(3930) and X(4160). These poles appear with quantum numbers I=0 and $J^{PC}=0^{++},2^{++}$ and $2^{++}$, respectively, and can be considered as hadronic molecules made of $D^*\bar{D}^*$, $D_s^*\bar{D}^*_s$.Comment: to appear in Proceedings of XIII International Conference on Hadron Spectroscopy, November 29 - December 4, 2009, Florida State Universit

Improved Fixed Center Approximation of the Faddeev equations for the KˉNN\bar{K}NN system with S=0

We extend the Fixed Center Approximation (FCA) to the Faddeev Equations for the $\bar{K} NN$ system with S=0, including the charge exchange mechanisms in the $\bar{K}$ rescattering which have been ignored in former works within the FCA. We obtain similar results to those found before, but the binding is reduced by 6 MeV. At the same time we also evaluate the explicit contribution the $\pi N \Sigma$ intermediate state in the three body system and find that it produces and additional small decrease in the binding of about 3 MeV. The system appears bound by about 35 MeV and the width omitting two body absorption, is about 50 MeV.Comment: 12 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1102.285

Baryonic Resonances from Baryon Decuplet-Meson Octet Interactions and the Exotic Resonance S=1, I=1, J^P=3/2-

Using the lowest order chiral Lagrangian we study s-wave interactions of the baryon decuplet with the octet of pseudoscalar mesons. We find two bound states in the flavour SU(3) limit corresponding to the octet and decuplet representations. These are found to split into eight different trajectories in the complex plane when the SU(3) symmetry is broken gradually. Finally, we are able to provide a reasonable description for a good number of 4-star 3/2- resonances listed by the Particle Data Group. In particular, the Xi(1820), the Lambda(1520) and the Sigma(1670) states are well reproduced. We predict a few other resonances and also evaluate the couplings of the observed resonances to the various channels from the residues at the poles of the scattering matrix from where partial decay widths into different channels can be evaluated.Comment: Talk given at 10th International Conference on the Structure of Baryons (Baryon 2004) at Palaiseau (France), 25-29 October 200