Search results for "Unitary state"
showing 10 items of 133 documents
Polarized structure functions of the nucleon in the resonance region
2000
Abstract We present predictions for the spin structure functions of the proton in the framework of a unitary isobar model for one-pion photo- and electroproduction. Our results are compared with recent experimental data from SLAC. The first moments of the calculated structure functions fullfil the Gerasimov-Drell-Hearn and Burkhardt-Cottingham sum rules within an error of typically 5–10%.
Binding of charmonium with two- and three-body nuclei
2006
The energies of the (eta_c d) and (eta_c 3He) bound states are calculated on the basis of exact three- and four-body AGS equations. For the eta_c N interaction a Yukawa-type potential has been adopted. The calculations are done for a certain range of its strength parameter. The results obtained are quite different from calculations based on the folding model.
Structure of Λ(1405) and chiral dynamics
2005
We report on a recent theoretical work on the structure of the Λ(1405) resonance within a chiral unitary approach, in which the resonance is dynamically generated in meson-baryon scattering. Studying the analytic structure of the scattering amplitude, we have found that there are two poles lying around energies of Λ(1405) with different widths and couplings to the meson-baryon states. We discuss reactions to conform the double pole structure in experiment and elastic K − p scattering at low energies.
Low-lying resonances from chiral unitary dynamics
2003
Abstract The s-wave meson-baryon interaction is studied using the lowest-order chiral lagrangian in a unitary coupled-channels Bethe-Salpeter equation. The resonances belonging to the low-lying J P = 1 2 − octet, the N (1535), Λ(1620) and Ξ(1620), together with the Λ(1405) singlet, are generated dynamically through multiple meson-baryon scattering. The Λ(1405) appears as a mixture of K N and πΣ quasibond states, while the Λ(1670) is a K Ξ quasibond state. Arguments are given to assigne J P = 1 2 − to the unmeasured spin and parity of the Ξ(1620).
Scalar resonances in the D+→K−K+K+ decay
2021
We study theoretically the resonant structure of the double Cabibbo suppressed $D^+\to K^- K^+K^+$ decay. We start from an elementary production diagram, considered subleading in previous approaches, which cannot produce a final $K^- K^+$ pair at the tree level but which we show to be able to provide the strength of the decay through final meson-meson state interaction. The different meson-meson elementary productions are related through SU(3) and the final rescattering is implemented from a suitable implementation of unitary extensions of ChPT which generate dynamically the scalar resonances $f_0(980)$ and $a_0(980)$. We obtain a good agreement with recent experimental data from the LHCb c…
Chiral unitary theory: Application to nuclear problems
2001
In this talk we briefly describe some basic elements of chiral perturbation theory, $\chi PT$, and how the implementation of unitarity and other novel elements lead to a better expansion of the $T$ matrix for meson meson and meson baryon interactions. Applications are then done to the $ \pi \pi $ interaction in nuclear matter in the scalar and vector channels, antikaons in nuclei and $K^-$ atoms, and how the $\phi$ meson properties are changed in a nuclear medium.
Study of the ππ system in a finite volume
2014
We evaluate energy levels of the ππ system in the ρ channel in a finite volume using chiral unitary theory. We investigate ππ phase shifts and ρ meson properties using Lattice QCD data with high precision. We also shortly discuss the πK system in the K* channel in a finite volume.
Nonperturbative approach to effective chiral Lagrangians and meson interactions
1998
We develop a coupled channel unitary approach describing the behavior at higher energies of systems whose low-energy dynamics is given by effective O(p^2) and O(p^4) chiral Lagrangians. Our free parameters are those of the O(p^4) Lagrangian. When applied to the meson-meson interaction, it yields a remarkable agreement with data up to sqrt{s}=1.2 GeV, dynamically generating the sigma, f_0, a_0,rho and K^* resonances. Further applications are also proposed.
Chiral dynamics of baryon resonances and hadrons in a nuclear medium
2005
In these lectures I make an introduction to chiral unitary theory applied to the meson baryon interaction and show how several well known resonances are dynamically generated, and others are predicted. Two very recent experiments are analyzed, one of them showing the existence of two $\Lambda(1405)$ states and the other one providing support for the $\Lambda(1520)$ resonance as a quasibound state of $\Sigma(1385) \pi$. The use of chiral Lagrangians to account for the hadronic interaction at the elementary level introduces a new approach to deal with the modification of meson and baryon properties in a nuclear medium. Examples of it for $\bar{K}$, $\eta$ and $\phi$ modification in the nuclea…
Latest Results for the Antikaon-Nucleon Optical Potential
2010
The key question of this letter is whether the K-nucleus optical potential is deep, as it is prefered by the phenomenological fits to kaonic atoms data, or shallow, as it comes out from unitary chiral model calculations. The current experimental situation is reviewed.