Search

Theoretical studies within the chiral unitary approach, and recent experiments, have provided evidence of the existence of two isoscalar states in the region of the Λ(1405). In this paper we use the same chiral approach to generate energy levels in a finite box. In a second step, assuming that these energies correspond to lattice QCD results, we devise the best strategy of analysis to obtain the two states in the infinite-volume case, with sufficient precision to distinguish them. We find out that by using energy levels obtained with asymmetric boxes and/or with a moving frame, with reasonable errors in the energies, one has a successful scheme to get the two Λ(1405) poles. [ABSTRACT FROM AUTHOR]

We perform a calculation for the three-body NK¯K scattering amplitude by using the fixed-center approximation to the Faddeev equations, taking the interaction between N and K¯, N and K, and K¯ and K from the chiral unitary approach. The resonant structures show up in the modulus squared of the three-body scattering amplitude and suggest that a NK¯K hadron state can be formed. Our results are in agreement with others obtained in previous theoretical works, which claim a new N* resonance around 1920 MeV with spin-parity JP = 1/2+. The existence of these previous works allows us to test the accuracy of the fixed center approximation in the present problem and sets the grounds for possible application in similar problems, as an explorative tool to determine bound or quasibound three-hadron systems. [ABSTRACT FROM AUTHOR]

We evaluate the “σ " exchange contribution to the ¯ N → ¯ N scattering within a chiral unitary approach. We show that the chiral transition potentials for ππ → K¯ in the t -channel lead to a “σ " contribution that vanishes in the ¯ forward direction and, hence, would produce a null “σ " exchange contribution to the K- optical potential in nuclear matter in a simple impulse approximation. This is a consequence of the fact that the leading-order chiral Lagrangian gives an I = 0 ππ → K¯ amplitude proportional to the squared momentum transfer, q2. This finding poses questions on the meaning or the origin of “σ " exchange potentials used in relativistic mean-field approaches to the K- nuclear self-energy. This elementary “σ ” exchange potential in ¯ N → ¯ N is compared to the Weinberg-Tomozawa term and is found to be smaller than the present theoretical uncertainties but will be relevant in the future when aiming at fitting increasingly more accurate data. [ABSTRACT FROM AUTHOR]