arXiv subjects

E. Oset

Publications and source records attributed to E. Oset.

At least 397 records · Page 22Linked to original sources

arXiv2004

Radiative vector meson decay

We study the radiative $ρ$, $ω$ and $ϕ$ decay into $π^0 π^0 γ$ and $π^0 ηγ$ taking into account mechanisms in which there are two sequential vector-vector-pseudoscalar or axial-vector--vector--pseudoscalar steps followed by the coupling of a vector meson to the photon, considering the final state interaction of the two mesons. Other mechanisms in which two kaons are produced through the same sequential mechanisms or from vector meson decay into two kaons which undergo final state interaction leading to the final pair of pions or $π^0 η$, are also considered. The results of the parameter free theory, together with the theoretical uncertainties, are compared with the latest experimental results at Frascati and Novosibirsk.

hep-ph↗

arXiv2004

Dynamically Generated Resonances in the Chiral Unitary Approach to Meson Baryon Interaction

In this talk we report on the use of a chiral unitary approach for the interaction of the octets of meson and baryon and the octet of mesons with the decuplet of baryons. Two octets of $J^π=1/2^-$ baryon states and a singlet are generated dynamically in the first case, resulting in the case of strangeness $S=-1$ in two poles of the scattering matrix close to the nominal $Λ(1405)$ resonance. In the second case many resonances are also generated, among them an exotic baryon with S=1 corresponding to a $ΔK$ resonance. We make suggestions of experiments which could show evidence for the existence of these states.

hep-ph↗

arXiv2004

Unitary chiral dynamics in $J/Ψ$ decays into $VPP$ and the role of the scalar mesons

We make a theoretical study of the $\J$ decays into $ωππ$, $ϕππ$, $ωK \bar{K}$ and $ϕK\bar{K}$ using the techniques of the chiral unitary approach stressing the important role of the scalar resonances dynamically generated through the final state interaction of the two pseudoscalar mesons. We also discuss the importance of new mechanisms with intermediate exchange of vector and axial-vector mesons and the role played by the OZI rule in the $\Jϕππ$ vertex, quantifying its effects. The results nicely reproduce the experimental data for the invariant mass distributions in all the channels considered.

hep-ph↗

arXiv2004

Sigma meson mass and width at finite density

The sigma meson mass and width are studied at finite baryonic density in the framework of a chiral unitary approach which successfully reproduces the meson meson phase shifts and generates the f0 and sigma resonances in vacuum.

nucl-th↗

arXiv2004

Hadronic aspects of exotic baryons

In this talk I look into three different topics, addressing first the possibility that the $Θ^+$ is a bound state of $K πN$, exploiting the results of this study to find out the contribution of two meson and one baryon components in the baryon antidecuplet and in the third place I present results on a new resonant exotic baryonic state which appears as dynamically generated by the Weinberg Tomozawa $ΔK$ interaction.

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arXiv2004

Interaction of the $Θ^+$ with the nuclear medium

We study the selfenergy of the $Θ^+$ pentaquark in nuclei associated with two types of interaction: the KN decay of the $Θ^+$ and two meson baryon decay channels of the $Θ^+$. Whereas the potential related to the first source is quite weak, the second kind of interaction produces a large and attractive potential that could lead to the existence of $Θ^+$ nuclear bound states.

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arXiv2004

$Λ(1405)$ and $\barΛ(1405)$ in $J/ψ$ four-body decays

We study the structure of the baryon resonances $Λ(1405)$ and $\barΛ(1405)$ in $J/ψ$ four body decays $J/ψ\to Σ\bar Σππ$ in the framework of a coupled channel chiral unitary approach. With still sufficient freedom for model parameters, the $Λ(1405)$ and $\barΛ(1405)$ resonances are generated by simultaneously taking the meson baryon and meson anti-baryon final state interactions into account. The $πΣ$ ($π\barΣ$) invariant mass distributions peak around 1410 MeV, which favors the assertion that the $Λ(1405)$ ($\barΛ(1405)$) is a superposition of the two $Λ(1405)$ ($\barΛ(1405)$) states which dominantly couple to $\bar K N$ ($K\bar N$) and $πΣ$ ($π\barΣ$), respectively. We also calculate the amplitude for isospin I=1 which gives hints on a possible I=1 baryon resonance in the energy region of the $Λ(1405)$, which up to now has not been observed.

nucl-th↗

arXiv2004

Decay of axial-vector mesons into VP and P$γ$

We propose a phenomenological Lagrangian for the decay of the SU(3) nonets of the axial-vector mesons of $J^{PC}=1^{+-},1^{++}$ into a vector meson and a pseudoscalar constructed with tensor fields for the vector and axial-vector mesons. The formulation leads to a good reproduction of the different decay branching ratios and assuming vector meson dominance (VMD) it also leads to good results for the radiative decay of the $a_1$ into pion and photon, and in agreement with the structure proposed in the chiral tensor formulation of radiative decay of axial-vector mesons. The two SU(3) parameters and the mixing angle of $K_{1A}$ and $K_{1B}$ needed to give the physical $K_1(1270)$ and $K_1(1400)$ resonances are also determined.

hep-ph↗

arXiv2004

S-wave pion nucleon scattering lengths from $πN$, pionic hydrogen and deuteron data

The isoscalar and isovector scattering lengths (b_0,b_1) are determined using a unitarized coupled channel approach based on chiral Lagrangians. Using experimental values of pionic hydrogen and deuterium as well as low energy pi N scattering data, the free parameters of the model are calculated. Isospin violation is incorporated to a certain extent by working with physical particle masses. For the deuterium scattering length a_{pi-d} new significant corrections concerning real and imaginary parts are evaluated, putting new constraints from pi-d scattering on the values of (b_0,b_1). In particular, dispersion corrections, the influence of the Delta(1232) resonance, crossed terms and multiple scattering in a Faddeev approach are considered.

nucl-th↗

arXiv2004

Chiral dynamics of the two Lambda(1405) states

The Lambda(1405) resonance is studied by a chiral unitary approach, in which the resonance is dynamically generated in coupled-channel meson-baryon scattering. Investigating the analytic structure of the scattering amplitudes obtained by the chiral unitary approach, we find two poles around the energies of the Lambda(1405) coupling differently to the meson-baryon states. We reach the conclusion that the Lambda(1405) resonance seen in experiments is not just one single resonance, but a superposition of these two states.

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arXiv2004

Unitary chiral dynamics in J/Psi to VPP decays and the role of scalar mesons

We make a theoretical study of the J/Psi decays into ωππ, ϕππ, ωK \bar{K} and ϕK\bar{K} using the techniques of the chiral unitary approach stressing the important role of the scalar resonances dynamically generated through the final state interaction of the two pseudoscalar mesons. We also discuss the importance of new mechanisms with intermediate exchange of vector and axial-vector mesons and the role played by the OZI rule in the J/Ψϕππvertex, quantifying its effects. The results nicely reproduce the experimental data for the invariant mass distributions in all the channels considered.

hep-ph↗

arXiv2004

On the determination of $Θ^+$ quantum numbers and other topics of exotic baryons

In this talk I look into three different topics, addressing first a method to determine the quantum numbers of the $Θ^+$, then exploiting the possibility that the $Θ^+$ is a bound state of $K πN$ and in the third place I present results on a new resonant exotic baryonic state which appears as dynamically generated by the Weinberg Tomozawa $ΔK$ interaction.

hep-ph↗

arXiv2004

Photoproduction of $K^*$ for the study of $Λ(1405)$

The photo-induced $K^*$ vector meson production is investigated for the study of the $Λ(1405)$ resonance. This reaction is particularly suited to the isolation of the second pole in the $Λ(1405)$ region which couples dominantly to the $\bar K N$ channel. We obtain the mass distribution of the $Λ(1405)$ which peaks at 1420 MeV, and differs from the nominal one. Combined with several other reactions, like the $π^- p \to K^0 πΣ$ which favours the first pole, this detailed study will reveal a novel structure of the $Λ(1405)$ state.

nucl-th↗

arXiv2004

Study of $Λ(1405)$ in photoproduction of $K^*$

We investigate the photoproduction of $K^*$ vector meson for the study of the $Λ(1405)$ resonance. The invariant mass distribution of $πΣ$ shows a different shape from the nominal one, peaking at 1420 MeV. This is considered as a consequence of the double pole structure of $Λ(1405)$, predicted in the chiral unitary model. Combined with other reactions, such as $π^- p \to K^0 πΣ$, experimental confirmation of this fact will reveal a novel structure of the $Λ(1405)$ state.

nucl-th↗

arXiv2004

Is the Theta+ a K pi N bound state?

Following a recent suggestion that the $Θ^+$ could be a $K πN$ bound state we perform an investigation under the light of the meson meson and meson baryon dynamics provided by the chiral Lagrangians and using methods currently employed to dynamically generate meson and baryon resonances by means of unitary extensions of chiral perturbation theory. We consider two body and three body forces and examine the possibility of a bound state below the three particle pion-kaon-nucleon and above the kaon-nucleon thresholds. Although we find indeed an attractive interaction in the case of isospin I=0 and spin-parity $1/2^+$, the interaction is too weak to bind the system. If we arbitrarily add to the physically motivated potential the needed strength to bind the system and with such strong attraction evaluate the decay width into $K N$, this turns out to be small. A discussion on further work in this direction is done.

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arXiv2003

Using the $K^+p\to π^+K^+n$ reaction to determine the $Θ^+$ quantum numbers

We study the $K^+p\to π^+K^+n$ reaction with some kinematics suited to the production of the $Θ^+$ resonance recently observed and show that the measurement of cross sections and polarization observables can shed light on the spin,isospin and parity of the $Θ^+$ state.

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arXiv2003

Dynamical Generation of Hyperon Resonances

In this talk we report on how, using a chiral unitary approach for the meson--baryon interactions, two octets of $J^π=1/2^-$ baryon states and a singlet are generated dynamically, resulting in the case of strangeness $S=-1$ in two poles of the scattering matrix close to the nominal $Λ(1405)$ resonance. We suggest experiments which could show evidence for the existence of these states.

nucl-th↗

arXiv2003

Light scalar mesons in $J / psi ->$NN$meson meson$ decays in a chiral unitary approach

We study the four-body decays $J/ψ\to N {\bar N}$ {\it meson meson} using a chiral unitary approach to account for the meson meson final state interaction (FSI). The calculation of the $J/ψ\to N \bar N π^+ π^-$ process properly reproduces the experimental data after taking the FSI of mesons and the contribution of intermediate $ρ$ meson into account. The isoscalar resonances $σ$, $f_0(980)$ and the isovector resonance $a_0(980)$ are generated through the FSI of the mesons in the channels $J/ψ\to N \bar N π^0 π^0$ and $J/ψ\to N \bar N π^0 η$, respectively. We also calculate the two mesons invariant mass distribution and the partial decay width of $J/ψ\to N \bar N K^+ K^-$ and $J/ψ\to N \bar N K^0 {\bar K}^0$, on which there is still no experimental data available.

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