Erasmo Ferreira

Efimov effect and higher bound states in a three-particle system☆

Abstract We study the J = 0 bound states for a system of three identical spinless particles interacting in pairs through delta-shell potentials. The Efimov states are identified, and their wave functions obtained. We have found a new family of bound states, which occur for higher values of the attractive coupling strength.

Constrained phase analysis of pion-deuteron scattering

Abstract A relativistic three-body theory of the NNπ system is applied to predict πD elastic scattering. Phase shifts and inelastic parameters are compared with those of a multiple scattering calculation.

K+p scattering with unitary Padé approximant

The K+p system is studied with the Pade approximants method. From a Lagrangian written in terms of kaon, nucleon and hyperon fields we evaluate the [1,1] Pade approximant for the s, p12 and p32 waves. Our results for differential and total cross sections, polarization and phase shifts are compared with experimental data at low energies and with solutions of phase-shift analyses. We find that the model describes very satisfactorily all the available data on the K+p interaction at low energies.

Effective lagrangian for kaon-nucleon scattering

Abstract We investigate a model for the kaon-nucleon interaction based on a lagrangian which includes the Yukawa interactions of hyperons, kaons and nucleons plus contact terms representing short-range interactions in each isospin state. We evaluate all diagrams up to fourth order and unitarize the partial-wave S -matrix elements through diagonal Pade approximants. The results of the calculations with this model give a good description of all experimental data on both I =0 and I =1 states of the KN system at low and intermediate energies.

Low-energy kaon-nucleon scattering in the I = 0 state

Abstract The KN system in the I = 0 state is studied with the method of Pade approximants. The treatment follows the lines of the previous work of the same authors on the I = 1 interaction. From the same Lagrangian, the unitary [1,1] Pade approximants for the scattering functions in the s, p 1 2 and p 3 2 waves are calculated at low energies in terms of a single coupling constant. The model predicts negative and rather strong s-wave scattering lengths and phase shifts, while the two p-waves are small and of opposite signs. The differential and total cross sections for elastic and charge-exchange processes in K+ scattering by neutrons and the differential polarization in K+n → K0p are compared with data extracted from experiments on K+ scattering by deuterons. The model predicts that the cross section in the I = 0 state decreases slowly with energy.

Regge trajectories for a velocity dependent potential

We study the distribution of the singularities in the complex angular momentum plane of the S matrix for a velocity‐dependent potential, and note some deviations with respect to the general behavior established for static potentials. We analyze the physical implications of our results concerning the existence of bound states and resonances.

Multiple scattering calculations in πd elastic scattering

Some results are presented of multiple scattering analyses of ..pi..-d data. It is found that special attention must be given to the indeterminacy in the values of the kinematic variables entering in the evaluation of the two-particle amplitudes. (SDF)

Pion deuteron elastic scattering

An extensive analysis is presented of the existing experimental data on pion-deuteron elastic scattering at low energies, in the framework of the multiple scattering series. The single scattering and the double scattering terms are evaluated, accounting for nucleon recoil and fermi-motion effects. The effects of the kinematical ambiguities in the use of the two-body ..pi..N amplitudes are studied.