arXiv subjects

E. Oset

Publications and source records attributed to E. Oset.

At least 379 records · Page 21Linked to original sources

arXiv2005

Study of a possible S=+1 dynamically generated baryonic resonance

Starting from the lowest order chiral Lagrangian for the interaction of the baryon decuplet with the octet of pseudoscalar mesons we find an attractive interaction in the $ΔK$ channel with L=0 and I=1, while the interaction is repulsive for I=2. The attractive interaction leads to a pole in the second Riemann sheet of the complex plane and manifests itself in a large strength of the $ΔK$ scattering amplitude close to the $ΔK$ threshold, which is not the case for I=2. However, we also make a study of uncertainties in the model and conclude that the existence of this pole depends sensitively upon the input used and can disappear within reasonable variations of the input parameters. We take advantage to study the stability of the other poles obtained for the ${3/2}^-$ dynamically generated resonances of the model and conclude that they are stable and not contingent to reasonable changes in the input of the theory.

nucl-th↗

arXiv2005

Inclusive Quasi-Elastic Neutrino Reactions

The Quasi-Elastic contribution of the nuclear inclusive electron scattering model developed in Nucl. Phys. A 627 (1997) 543 is extended to the study of electroweak Charged Current induced nuclear reactions, at intermediate energies of interest for future neutrino oscillation experiments. The model accounts for long range nuclear (RPA) correlations, Final State Interaction and Coulomb corrections. RPA correlations are shown to play a crucial role in the whole range of neutrino energies, up to 500 MeV, studied in this work. Predictions for inclusive muon capture for different nuclei, and for the reactions $^{12}$C$(ν_μ,μ^-)X$ and $^{12}$C$(ν_e,e^-)X$ near threshold are also given.

nucl-th↗

arXiv2005

Production of $Θ^+$ Hypernuclei with the $(K^+,π^+)$ reaction

We present results on the production of bound states of $Θ^+$ in nuclei using the $(K^+,π^+)$ reaction. By taking into account the states obtained within a wide range of strength of the $Θ^+$ nucleus optical potential, plus the possibility to replace different nucleons of the nucleus, we obtain an excitation spectra with clearly differentiated peaks. The magnitude of the calculated cross sections is well within reachable range.

nucl-th↗

arXiv2005

Evaluation of the $ππ$ scattering amplitude in the $σ$-channel at finite density

The $ππ$ scattering amplitude in the $σ$-channel is studied at finite baryonic density in the framework of a chiral unitary approach which successfully reproduces the meson meson phase shifts and generates the $f_0$ and $σ$ resonances in vacuum. We address here a new variety of mechanisms recently suggested to modify the $ππ$ interaction in the medium, as well as the role of the $s-$wave selfenergy, in addition to the $p-$wave, in the dressing of the pion propagators.

nucl-th↗

arXiv2005

Evidence for the two pole structure of the Lambda(1405) resonance

The K^- p --> pi^0 pi^0 Sigma^0 reaction is studied within a chiral unitary model. The distribution of pi^0 Sigma^0 states forming the Lambda(1405) shows, in agreement with a recent experiment, a peak at 1420 MeV and a relatively narrow width of Gamma = 38 MeV. The mechanism for the reaction is largely dominated by the emission of a pi^0 prior to the K^- p interaction leading to the Lambda(1405). This ensures the coupling of the Lambda(1405) to the K^- p channel, thus maximizing the contribution of the second state found in chiral unitary theories, which is narrow and of higher energy than the nominal Lambda(1405). This is unlike the pi^- p --> K^0 πSigma reaction, which gives more weight to the pole at lower energy and with a larger width. The data of these two experiments, together with the present theoretical analysis, provides a firm evidence of the two pole structure of the Lambda(1405).

hep-ph↗

arXiv2005

Dynamical baryon resonances from chiral unitarity

We report on the latests developments in the field of baryonic resonances generated from the meson-baryon interaction in coupled channels using a chiral unitary approach. The collection of resonances found in different strangeness and isospin sectors can be classified into SU(3) multiplets. The Lambda(1405) emerges as containing the effect of two poles of the scattering amplitude and various reactions that might preferentially select one or the other pole are discussed.

nucl-th↗

arXiv2005

Chiral dynamics of hadrons in nuclei

In this talk I report on selected topics of hadron modification in the nuclear medium using the chiral unitary approach to describe the dynamics of the problems. I shall mention how antikaons, $η$, and $ϕ$ are modified in the medium and will report upon different experiments done or planned to measure the $ϕ$ width in the medium.

nucl-th↗

arXiv2005

Two-meson cloud contribution to the baryon antidecuplet self-energy

We study the self-energy of the SU(3) antidecuplet coming from two-meson virtual clouds. Assuming that the exotic Theta+ belongs to an antidecuplet representation with N(1710) as nucleon partner, we derive effective Lagrangians that describe the decay of N(1710) into N pi pi with two pions in s- or p-wave. It is found that the self-energies for all members of the antidecuplet are attractive, and the larger strangeness particle is more bound. From two-meson cloud, we obtain about 20 % of the empirical mass splitting between states with different strangeness.

hep-ph↗

arXiv2005

Bound states of $Θ^+$ in nuclei

We study the binding energy and the width of the $Θ^+$ in nuclei, associated to the $K N$ and $ K πN$ components. The first one leads to negligible contributions while the second one leads to a sizeable attraction, enough to bind the $Θ^+$ in nuclei. Pauli blocking and binding effects on the $K N$ decay reduce considerably the $Θ^+$ decay width in nuclei and medium effects associated to the $ K πN$ component also lead to a very small width, as a consequence of which one finds separation between the bound levels considerably larger than the width of the states.

nucl-th↗

arXiv2005

$Θ^+$ Hypernuclei

We present results for the selfenergy of the $Θ^+$ pentaquark in nuclei associated with two sources: the $KN$ decay of the $Θ^+$ and the two meson baryon decay channels of the $Θ^+$ partners in an antidecuplet of baryons. The first source is shown to produce a small potential, unable to bind the $Θ^+$ in nuclei, while the second source gives rise to a large attractive potential. At the same time we show that the width of the $Θ^+$ in nuclei is small, such that, in light and medium nuclei, many bound $Θ^+$ states would appear with a separation between levels appreciably larger than the width of the states, thus creating an ideal scenario for pentaquark spectroscopy in nuclei.

nucl-th↗

arXiv2005

Baryonic Resonances from Baryon Decuplet-Meson Octet Interactions and the Exotic Resonance S=1, I=1, J^P=3/2-

Using the lowest order chiral Lagrangian we study s-wave interactions of the baryon decuplet with the octet of pseudoscalar mesons. We find two bound states in the flavour SU(3) limit corresponding to the octet and decuplet representations. These are found to split into eight different trajectories in the complex plane when the SU(3) symmetry is broken gradually. Finally, we are able to provide a reasonable description for a good number of 4-star 3/2- resonances listed by the Particle Data Group. In particular, the Xi(1820), the Lambda(1520) and the Sigma(1670) states are well reproduced. We predict a few other resonances and also evaluate the couplings of the observed resonances to the various channels from the residues at the poles of the scattering matrix from where partial decay widths into different channels can be evaluated.

nucl-th↗

arXiv2005

Resonances from Baryon decuplet-Meson octet interaction

The s-wave interactions of the baryon decuplet with the octet of pseudoscalar mesons is studied in a unitarized coupled channel approach. We obtain a fair agreement for mass and width of several 3/2- resonances. In particular, the Xi(1820), the Lambda(1520) and the Sigma(1670) states are well reproduced. Other resonances are predicted and also the couplings of the observed resonances to the various channels are evaluated.

nucl-th↗

arXiv2005

Structure of Lambda(1405) and chiral dynamics

We report on a recent theoretical work on the structure of the Lambda(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 Lambda(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.

hep-ph↗

arXiv2005

Determining the $Θ^+$ quantum numbers through a Kaon induced reaction

We study the $K^+p\to π^+KN$ reaction with kinematical condition suited to the production of the $Θ^+$ resonance. It is shown that in this reaction with the polarization experiment, a combined consideration of the strength at the peak and the angular dependence of cross section can help determine the $Θ^+$ quantum numbers.

nucl-th↗

arXiv2005

Baryonic Resonances from Baryon Decuplet-Meson Octet Interaction

We study $S$-wave interactions of the baryon decuplet with the octet of pseudoscalar mesons using the lowest order chiral Lagrangian. In the S=1 sector, we find an attractive interaction in the $ΔK$ channel with I=1 while it is repulsive for I=2. The attractive interaction leads to a pole in the second Riemann sheet of the complex plane and is manifested as a large strength in the scattering amplitude close to the $ΔK$ threshold, which is not the case for I=2. We use the unitarized coupled channel approach to also investigate all the other possible values of strangeness and isospin. We find two bound states in the SU(3) limit corresponding to the octet and decuplet representations. These are found to split into eight different trajectories in the complex plane when the SU(3) symmetry is broken gradually. Finally, we are able to provide a reasonable description for a good number of 4-star ${3/2}^-$ resonances listed by the Particle Data Group. In particular, the $Ξ(1820)$, the $Λ(1520)$ and the $Σ(1670)$ states are well reproduced. We predict a few other resonances and also evaluate the couplings of the observed resonances to the various channels from the residues at the poles of the scattering matrix from where partial decay widths into different channels can be evaluated.

nucl-th↗

arXiv2004

Measuring the $ϕ$ meson width in the medium from $p$ induced $ϕ$ production in nuclei

We study the $A$ dependence of the $ϕ$ meson production cross section in proton nucleus reactios at energies just above threshold, which are accessible in an experimental facility like COSY. This $A$ dependence has two sources: the distortion of the incident proton and the absorption of the $ϕ$ in its way out of the nucleus. This second process reduces the cross section in about a factor two in heavy nuclei. Thus we show that the $A$ dependence of the cross section contains valuable information on the $ϕ$ width in the nuclear medium.

nucl-th↗

arXiv2004

$Θ^+$ pentaquark in the nuclear medium

We study the interaction of the $Θ^+$ pentaquark with nuclear matter associated to the $KN$ decay channels and to the two meson cloud. We find that the potential is attractive and could be strong enough to lead to the existence of $Θ^+$ nuclear bound states.

nucl-th↗

arXiv2004

Testing the nature of the $Λ(1520)$ resonance through photoproduction

Recent studies within the framework of chiral unitary theory produce the $Λ(1520)$ resonance, among several others, as a dynamically generated resonance from the interaction of the baryon decuplet and the meson octet. The $Λ(1520)$ qualifies as a quasibound state of $πΣ(1385)$ and this has repercussion in some observable quantities. In the present work we show that the $γp\to K^+K^-p$ reaction has a sizeable cross section for invariant $K^-p$ masses above the $Λ(1520)$ mass. On the other hand, we also find that the $γp\to K^+πΣ(1385)$ reaction has a sizeable cross section in that energy region as a consequence of the strong coupling of the $Λ(1520)$ to $πΣ(1385)$, and then we make predictions for the ratio of this cross section to that of the $γp\to K^+ K^-p $ reaction.

hep-ph↗