Bound states of Θ+\Theta^+ in nuclei

We study the binding energy and the width of the $\Theta^+$ in nuclei, associated to the $K N$ and $K \pi N$ components. The first one leads to negligible contributions while the second one leads to a sizeable attraction, enough to bind the $\Theta^+$ in nuclei. Pauli blocking and binding effects on the $K N$ decay reduce considerably the $\Theta^+$ decay width in nuclei and medium effects associated to the $K \pi N$ component also lead to a very small width, as a consequence of which one finds separation between the bound levels considerably larger than the width of the states.Comment: Presentation in the 10th International Baryon Conference BARYON0

Phi meson mass and decay width in nuclear matter

The $\phi$ meson spectrum, which in vacuum is dominated by its coupling to the $\bar{K} K$ system, is modified in nuclear matter. Following a model based on chiral SU(3) dynamics we calculate the $\phi$ meson selfenergy in nuclear matter considering the $K$ and $\bar{K}$ in-medium properties. For the latter we use the results of previous calculations which account for $S-$ and $P-$wave kaon-nucleon interactions based on the lowest order meson-baryon chiral effective Lagrangian, and this leads to a dressing of the kaon propagators in the medium. In addition, a set of vertex corrections is evaluated to fulfill gauge invariance, which involves contact couplings of the $\phi$ meson to $S-$wave and $P-$wave kaon-baryon vertices. Within this scheme the mass shift and decay width of the $\phi$ meson in nuclear matter are studied.Comment: 19 pages, 10 figures in EPS format, revtex4; One section modified, some references update

A Coordinated EU Minimum Wage Policy?

[Excerpt] Minimum wages exist in all EU member states, even if, as we shall see in this report, they are set up and established in very different ways. Minimum wages, in fact, can be considered as a cornerstone of the “European Social Model”. Yet, the on-going process of European integration has so far had very little to do with them. Wages are explicitly excluded from the competences of European institutions in the existing treaties, contrary to other areas of work and employment such as working time or health and safety. But in the context of increasing European integration, it seems at least plausible that sooner or later there would be some attempt of coordinating this important aspect of social policy across countries. As we will see in this report, the idea has been discussed at the European level several times since the EU was born, and it seems to be gaining momentum the context of the current economic crisis. Of course, the discussion is by no means settled, as many important European and national actors consider that this area should remain within the remit of national governments and according to national traditions and practices. It is certainly possible that wages, and minimum wages, would remain squarely at the level of national competence in the foreseeable future. Still, it seems like a worthwhile exercise (useful to the debate) to explore what kind of implications would be associated with such a coordination of European minimum wage policy. This is what we will try to do in this report. Without taking ourselves a position, we will try to provide arguments and facts that we hope can be useful in this debate. The report is organized in two big sections. In the first one, we will discuss the theoretical and policy considerations around a coordinated EU minimum wage policy. We will review the social sciences literature on the effects of minimum wages, present a broad picture of the current debates around the coordination of EU minimum wage policy and discuss the institutional difficulties that such a coordination would in our view have to face. In other words, that section will try to provide a balanced summary of the theoretical and policy arguments around this debate. The second big section will try to complement the arguments with some facts, by carrying out a “simple accounting exercise” to evaluate how many and what types of workers would be most affected by a hypothetical coordination of minimum wage policy in the different countries, using a baseline scenario of a single national wage floor of 60% of the median national wages and drawing from the two most recent EU-wide data sources on wages and income. Eurofound was established in 1975 with the mandate of contributing with knowledge to the planning and design of better living and working conditions in Europe. We hope that this report can at least contribute to the debate

The baryon-decuplet in the chiral dynamics of Lambda-hyperons in nuclear matter

We study the long range part of the $\Lambda$-hyperon optical potential in nuclei using Quantum Many Body techniques and flavor-SU(3) Chiral Lagrangians as starting point. More precisely, we study the contributions to the $\Lambda$-hyperon optical potential due to the long-range two-pion exchange, with $\Sigma$ and $\Sigma^*$ baryons in the internal baryonic lines and considering Nh and $\Delta$h excitations. We also consider the contribution to the spin-orbit potentials that comes out from these terms. Our results support a natural explanation of the smallness of the $\Lambda$-nuclear spin-orbit interaction and shows the importance of the $\Sigma^*$ and $\Delta$ degrees of freedom for the hyperon-nucleus interactions.Comment: 8 pages, 5 figure

Baryonic Resonances from the Interactions of the Baryon Decuplet and Meson Octet

We study $S$-wave interactions of the baryon decuplet with the octet of pseudoscalar mesons using the lowest order chiral Lagrangian. We find two bound states in the 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: Contribution to the HADRON05 Conference, Rio de Janeiro, September 200

Threshold Neutral Pion Photoproduction on the Proton

The neutral pion photoproduction on the proton near threshold has a very small scattering cross section when compared to the charged channels, which in ChPT is explained by strong cancellations between the lowest order pieces. Therefore it is very sensitive to higher-order corrections of chiral perturbation theory. We perform a fully covariant calculation up to chiral order p^3 and we investigate the effect of the inclusion of the Delta(1232) resonance as an explicit degree of freedom. We show that the convergence improves, leading to a much better agreement with data at a wide range of energies.Comment: Proceedings to the NSTAR2015 conference, which will be published in JPS conference proceeding