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An analysis of the α + core properties of 104Te along with a global discussion on the α-cluster structure above the double-shell closures is presented from the viewpoint of the local potential model. The α + core interaction is described by a nuclear potential of (1 + Gaussian)×(W.S. + W.S.3) shape with two free parameters, which has been successfully tested in nuclei of different mass regions. The model produces Q α values and α-decay half-lives for 104Te in agreement with the 2018 experimental data of Auranen et al. in the energy range 5.13 MeV Q α 5.3 MeV using an α preformation factor P α = 1 . The comparison of the calculated reduced α-widths for the ground state bands of 104Te, 94Mo and 212Po indicates that 104Te has an α-cluster degree significantly higher than 94Mo and much higher than 212Po. These results point to 104Te as a preferential nucleus for α-clustering in the N , Z = 50 region and corroborate the statement on the superallowed α-decay in 104Te.

We have recently performed a relativistic O(q4) chiral expansion of the two-pion exchange NN potential, and explored its configuration space content by fitting the theoretical expressions to parametrized simply formulas. In order to test the applicability of our parametrized potential, we studied the pion plus production in proton-neutron scattering at threshold an compare our results to the ones given by Reid 93 and v18 potentials. We shown that our results are very close to the v18 potential, which means that the potential is reliable and trustful.

We outline the progress made in the past five years by the S\~ao Paulo group in the development of a two-pion exchange nucleon-nucleon potential within a Lorentz-invariant framework of (baryon) chiral perturbation theory., Comment: 5 pages, Talk given at the 18th International IUPAP Conference on Few-Body Problems in Physics, August 21-26 2006, Santos, Sao Paulo, Brazil

We assume that the nuclear potential for distances larger than 2.5 fm is given just by the exchanges of one and two pions and, for the latter, we adopt a model based on chiral symmetry and subthreshold pion-nucleon amplitudes, which contains no free parameters. The predictions produced by this model for nucleon-nucleon observables are calculated and shown to agree well with both experiment and those due to phenomenological potentials., Comment: 16 pages, 12 PS figures included, to appear in Physical Review C

We have recently performed a relativistic $O({q}^{4})$ chiral expansion of the two-pion exchange $NN$ potential, and here we explore its configuration space content. Interactions are determined by three families of diagrams, two of which involve just ${g}_{A}$ and ${f}_{\ensuremath{\pi}}$, whereas the third one depends on empirical coefficients fixed by subthreshold $\ensuremath{\pi}N$ data. In this sense, the calculation has no adjusted parameters and gives rise to predictions, which are tested against phenomenological potentials. The dynamical structure of the eight leading nonrelativistic components of the interaction is investigated and, in most cases, found to be clearly dominated by a well defined class of diagrams. In particular, the central isovector and spin-orbit, spin-spin, and tensor isoscalar terms are almost completely fixed by just ${g}_{A}$ and ${f}_{\ensuremath{\pi}}$. The convergence of the chiral series in powers of the ratio (pion mass∕nucleon mass) is studied as a function of the internucleon distance and, for $rg1\phantom{\rule{0.3em}{0ex}}\text{fm}$, found to be adequate for most components of the potential. An important exception is the dominant central isoscalar term, where the convergence is evident only for $rg2.5\phantom{\rule{0.3em}{0ex}}\text{fm}.$ Finally, we compare the spatial behavior of the functions that enter the relativistic and heavy baryon formulations of the interaction and find that, in the region of physical interest, they differ by about $5%$.

We show that chiral symmetry is responsible for large cancellations in the two-pion exchange nucleon-nucleon interaction, which are similar to those occuring in free pion-nucleon scattering., REVTEX style, 5 pages, 3 PostScrip figures compressed, tarred and uuencoded

We argue that the minimal chiral background for the two-pion exchange nucleon-nucleon interaction has nowadays a rather firm conceptual basis, which entitles it to become a standard ingredient of any modern potential. In order to facilitate applications, we present a parametrized version of a configuration space potential derived previously. We then use it to assess the phenomenological contents of some existing NN potentials., REVTEX style, 16 pages, 5 PostScript figures compressed, tarred and uuencoded

We evaluate the two pion exchange contribution to the nucleon-nucleon potential in configuration space using a minimal chiral model containing only pions and nucleons. The scalar-isoscalar component of the interaction is relatively small, due to cancellations between large terms, and fails to reproduce the intermediate range attraction in the central channel. We show that these results do not depend on how chiral symmetry is implemented.