0000000001039611
AUTHOR
José Antonio Oller Berber
Delta excitation in K+-nucleus collisions
We present calculations for \Delta excitation in the (K^+,K^+) reaction in nuclei. The background from quasielastic K^+ scattering in the \Delta region is also evaluated and shown to be quite small in some kinematical regions, so as to allow for a clean identification of the \Delta excitation strength. Nuclear effects tied to the \Delta renormalization in the nucleus are considered and the reaction is shown to provide new elements to enrich our knowledge of the \Delta properties in a nuclear medium.
Non-perturbative chiral approach to K(-)p ->gamma Y reactions
A recently developed nonperturbative chiral approach to describe the S=-1 meson-baryon reactions has been extended to investigate the near threshold K−p→γΛ,γΣ0 reactions. With the parameters governed by chiral SU(3) symmetry, we show that the predicted branching ratios ΓK−p→γΛ/ΓK−p→all and ΓK−p→γΣ0/ΓK−p→all are close to the experimental values. The coupling with the η channels, which was shown to be important in the S=−1 meson-baryon reactions, is also found to be significant here. Our results are consistent with the interpretation of the Λ(1405) as a quasi-bound meson-baryon state as found in other similar chiral approaches.
Pion and Kaon Vector Form Factors: a Chiral Unitary Approach
The pion and kaon coupled-channel vector form factors are described by making use of the resonance chiral Lagrangian results together with a suitable unitarization method in order to take care of the final state interactions. A very good reproduction of experimental data is accomplished for the vector form factors up to s√≤1.2 GeV and for the ππ P-wave phase shifts up to s√≤1.5 GeV.
Chiral symmetry in the KḰ and kn systems
In this talk we present teh results of recent developments in the aplication of Chiral perturbation theory to the KḰ system and to de K+N →KNπ reaction close to threshosd. In the first case, we study the decay channels of the a0 and f0 mesons assumed to be made largely from KḰ. In the second case comparison is made with the present data. A qualitative agreement with experiment is both in found cases. Oset Baguena, Eulogio, Eulogio.Oset@ific.uv.es, Nieves Pamplona, Juan Miguel, Juan.M.Nieves@ific.uv.es
Theoretical study of the gamma gamma -> meson-meson reaction
We present a unified picture which studies simultaneously the gamma gamma-->pi^+ pi^-, pi^0 pi^0, K^+ K^-, K^0 bar{K}^0, pi^0 eta reactions up to about sqrt(s)=1.4 GeV reproducing the experimental cross sections. The present work implements in an accurate way the final state interactions of the meson-meson system, which is shown to be essential in order to reproduce the data, particularly the L=0 channel. This latter channel is treated here following a recent theoretical work in which the meson-meson amplitudes are well reproduced and the f_0, a_0, sigma resonances show up clearly as poles of the t matrix. The present work, as done in earlier ones, also incorporates elements of chiral symme…
Meson–meson and meson–baryon interactions in a chiral non-perturbative approach
A qualitative account of the meson-meson and meson-baryon interactions using chiral Lagrangians and the inverse amplitude method in coupled channels is done. The method, imposing exact unitarity, proves to be a very useful tool to extend the information contained in the chiral Lagrangians at energies beyond the realm of applicability of chiral perturbation theory. Oset Baguena, Eulogio, Eulogio.Oset@ific.uv.es
Clues for the existence of two K-1(1270) resonances
The axial-vector meson K1(1270) was studied within the chiral unitary approach, where it was shown that it has a two-pole structure. We reanalyze the high-statistics WA3 experiment K-p-->K-pi+pi-p at 63 GeV, which established the existence of both K1(1270) and K1(1400), and we show that it clearly favors our two-pole interpretation. We also reanalyze the traditional K-matrix interpretation of the WA3 data and find that the good fit of the data obtained there comes from large cancellations of terms of unclear physical interpretation.