Scalar isoscalar part of the hyperon-nucleon interaction

We study the central part of the ΛN potential by considering the correlated and uncorrelated two-meson exchange besides the ω exchange contribution. The correlated two-meson is evaluated in a chiral unitary approach. We find that a short-range repulsion is generated by the correlated two-meson potential which also produces an attraction in the intermediate distance region. The uncorrelated two-meson exchange produces a sizeable attraction in all cases which is counterbalanced by ω exchange contribution.     

The radiative decay of the <Emphasis Type="Italic">Λ</Emphasis>(1405) and its two-pole structure

We evaluate theoretically the radiative decay widths into γΛ and γΣ ⁰ of the two poles of the Λ(1405) found in chiral unitary theories and we find quite different results for each of the two poles. We show that, depending on which reaction is used to measure the Λ(1405) radiative decays, one gives more weight to one or the other pole, resulting in quite different shapes in the γΛ(Σ ⁰) invariant-mass distributions. Our results for the high-energy pole agree with those of the empirical determination of the γΛ and γΣ ⁰ radiative widths (based on an isobar model fitting of the K^-p atom data), which are sometimes referred to as “experimental data”. We have made a detailed study of the K ^- p→π ⁰ γΛ(Σ ⁰) and π ^- p→K ⁰ γΛ(Σ ⁰) reactions and have shown that they, indeed, lead to different shapes for the γΛ(Σ ⁰) invariant-mass distributions.     

Short-range correlations in high-energy hadron collisions

High-energy collisions of hadrons on nuclei are studied by means of Glauber multiple scattering theory, using Jastrow correlated wave functions. To this end a cluster expansion is derived, and its convergence properties are studied. Calculations have been carried out for ⁴He and ¹⁶O nuclei, and they are compared with experimental data.     

Spin,parity, and nature of the xi(1620) resonance

Using a unitary extension of chiral perturbation theory with a lowest-order s-wave SU(3) chiral Lagrangian we study low-energy meson-baryon scattering in the strangeness S=-2 sector. A scattering-matrix pole is found around 1605 MeV which corresponds to an s-wave Xi resonance with J(P)=1/2(-). We identify this resonance with the Xi(1620) state, quoted by the Particle Data Group with I=1/2 but with unknown spin and parity. The addition of the S=-2 state to the recently computed Lambda(1670), Sigma(1620), and N(1535) states completes the octet of J(P)=1/2(-) resonances dynamically generated in this chiral unitary approach.     

Unitarized Chiral Perturbation Theory in a finite volume: Scalar meson sector

We develop a scheme for the extraction of the properties of the scalar mesons f ₀(600) , f ₀(980) , and a ₀(980) from lattice QCD data. This scheme is based on a two-channel chiral unitary approach with fully relativistic propagators in a finite volume. In order to discuss the feasibility of finding the mass and width of the scalar resonances, we analyze synthetic lattice data with a fixed error assigned, and show that the framework can be indeed used for an accurate determination of resonance pole positions in the multichannel scattering.     

���Ѧ� Interaction Leading to N* and ��* Resonances

We have performed a calculation for the three-body ????? system by using the fixed center approximation to Faddeev equations, taking the interaction between ?? and ??, ?? and ??, and ?? and ?? from the chiral unitary approach. We find several peaks in the modulus squared of the three-body scattering amplitude, indicating the existence of resonances, which can be associated to known I?=?1/2, 3/2 and J ^P ?=?1/2⁺, 3/2⁺ and 5/2⁺ baryon states.     

ρ-Meson coupling to the nucleon in the chiral bag model

The vector and tensor couplings of the ρ-meson to the nucleon are calculated by assuming the indirect coupling of the ρ-meson to the nucleon, through the pion cloud of the chiral bag model. Qualitative agreement with experiment is found at reasonable bag radii for both versions of the model: the cloudy bag model with pions in the interior, and the standard model with pions excluded from the bag.     

Divergence of the quark self-energy in the second quantized chiral bag model

When summing over the intermediate quark states of a spherical cavity, the quark self-energy of the chiral bag model, in lowest order of the pion coupling, is shown to generate a series of terms, each one growing linearly with the angular variable κ. However, there is a cancellation between terms for different κ, which finally leads to an overall linearly divergent series.