arXiv subjects

E. Oset

Publications and source records attributed to E. Oset.

At least 271 records · Page 15Linked to original sources

arXiv2010

Isospin breaking effects in the dynamical generation of the X(3872)

We have studied isospin breaking effects in the X(3872) resonance and found a natural explanation for the branching fraction of the X decaying to $J/ψ$ with two and three pions being close to unit. Within our framework the X(3872) is a dynamically generated resonance in coupled channels. We also study the relationship between the couplings of the resonance to the coupled channels with its wave function, which further helps us to understand the isospin structure of the resonance.

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arXiv2010

The Y(3940), Z(3930) and the X(4160) as dynamically generated resonances from the vector-vector interaction

We study the vector-vector interaction within the framework of the hidden gauge formalism for the sector with quantum numbers charm C=0 and strangeness S=0 in the region around 4000 MeV. We get five poles, three of which could be identified with the Y(3940), Z(3930) and X(4160). These poles appear with quantum numbers I=0 and $J^{PC}=0^{++},2^{++}$ and $2^{++}$, respectively, and can be considered as hadronic molecules made of $D^*\bar{D}^*$, $D_s^*\bar{D}^*_s$.

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arXiv2010

Scalar, axial-vector and tensor resonances from the $ρD^$, $ωD^$ interaction in the hidden gauge formalism

We apply a unitary approach together with a set of hidden-gauge Lagrangians to study the vector-vector interaction. We study the case of the $ρ$($ω$)$D^*$ interaction within the model. In $I=1/2$ we get strong enough attraction to bind the system. Concretely, we get one resonance for each spin $J=0,1,2$. For J=1 and 2 these resonances can be easily identified with the $D^*(2460)$ and $D^*(2640)$. Whereas the state for J=0 with mass $M\sim2600$ MeV is a prediction of the model. In $I=3/2$ we get a repulsive interaction and hence no exotic dynamically generated states.

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arXiv2010

Charmed mesons in nuclear matter

We obtain the properties of charmed mesons in dense matter using a coupled-channel approach which accounts for Pauli blocking effects and meson self-energies in a self-consistent manner. We study the behaviour of dynamically-generated baryonic resonances together with the open-charm meson spectral functions in this dense nuclear environment. We discuss the implications of the in-medium properties of open-charm mesons on the $D_{s0}(2317)$ and the predicted X(3700) scalar resonances, and on the formation of $D$-mesic nuclei.

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arXiv2010

$VPγ$ radiative decay of resonances dynamically generated from the vector meson-vector meson interaction

We evaluate the radiative decay into a vector a pseudoscalar and a photon of several resonances dynamically generated from the vector vector interaction. The process proceeds via the decay of one of the vector components into a pseudoscalar and a photon, which have an invariant mass distribution very different from phase space as a consequence of the two vector structure of the resonances. Experimental work along these lines should provide useful information on the nature of these resonances.

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arXiv2010

Couplings in coupled channels versus wave functions: application to the X(3872) resonance

We perform an analytical study of the scattering matrix and bound states in problems with many physical coupled channels. We establish the relationship of the couplings of the states to the different channels, obtained from the residues of the scattering matrix at the poles, with the wave functions for the different channels. The couplings basically reflect the value of the wave functions around the origin in coordinate space. In the concrete case of the X(3872) resonance, understood as a bound state of $\ddn$ and $\ddc$ (and $c.c.$), with the $\ddn$ loosely bound, we find that the couplings to the two channels are essentially equal leading to a state of good isospin I=0 character. This is in spite of having a probability for finding the $\ddn$ state much larger than for $\ddc$ since the loosely bound channel extends further in space. The analytical results, obtained with exact solutions of the Schrödinger equation for the wave functions, can be useful in general to interpret results found numerically in the study of problems with unitary coupled channels methods.

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arXiv2009

Radiative open charm decay of the Y(3940), Z(3930), X(4160) resonances

We determine the radiative decay amplitudes for decay into $D^*$ and $\bar{D} γ$, or $D^*_s$ and $\bar{D}_s γ$ of some of the charmonium like states classified as X,Y,Z resonances, plus some other hidden charm states which are dynamically generated from the interaction of vector mesons with charm. The mass distributions as a function of the $\bar{D} γ$ or $\bar{D}_s γ$ invariant mass show a peculiar behavior as a consequence of the $D^* \bar{D}^*$ nature of these states. The experimental search of these magnitudes can shed light on the nature of these states.

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arXiv2009

Deeply Bound Kaonic Clusters

In this talk I make a review on the theoretical and experimental situation around the deeply bound kaon clusters, the possible bound kaonic states of nuclear, rather than atomic nature. At the same time I discuss novel developments around other kind of bound kaon clusters, which include states of two mesons and one baryon, with either one or two kaons, and states of a vector meson and two kaons, which explain naturally the observed properties of the X(2175) and Y(4260) resonances.

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arXiv2009

Charmed hadrons in nuclear medium

We study the properties of charmed hadrons in dense matter within a coupled-channel approach which accounts for Pauli blocking effects and meson self-energies in a self-consistent manner. We analyze the behaviour in this dense environment of dynamically-generated baryonic resonances as well as the open-charm meson spectral functions. We discuss the implications of the in-medium properties of open-charm mesons on the $D_{s0}(2317)$ and the predicted X(3700) scalar resonances.

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arXiv2009

The (K-,p) reaction on nuclei with in-flight kaons

We perform a theoretical study of the spectrum of protons with kinetic energies of around 600 MeV, emitted following the interaction of 1 GeV/c kaons with nuclei. A recent experimental analysis of this (K-,p) reaction on 12C, based on the dominant quasielastic process, has suggested a deeply attractive kaon nucleus potential. Our Monte Carlo simulation considers, in addition, the one-and two-nucleon K- absorption processes producing hyperons that decay into πN pairs. We find that this kaon in-flight reaction is not well suited to determine the kaon optical potential due, essentially, to the limited sensitivity of the cross section to its strength, but also to unavoidable uncertainties from the coincidence requirement applied in the experiment. A shallow kaon nucleus optical potential obtained in chiral models is perfectly compatible with the observed spectrum.

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arXiv2009

Baryon Resonances

In this talk I show recent results on how many excited baryon resonances appear as systems of one meson and one baryon, or two mesons and one baryon, with the mesons being either pseudoscalar or vectors. Connection with experiment is made including a discussion on old predictions and recent results for the photoproduction of the $Λ(1405)$ resonance, as well as the prediction of one $1/2^+$ baryon state around 1920 MeV which might have been seen in the $γp \to K^+ Λ$ reaction.

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arXiv2009

Strange and charm mesons at FAIR

We study the properties of strange and charm mesons in hot and dense matter within a self-consistent coupled-channel approach for the experimental conditions of density and temperature expected for the CBM experiment at FAIR/GSI. The in-medium solution at finite temperature accounts for Pauli blocking effects, mean-field binding of all the baryons involved, and meson self-energies. We analyze the behaviour in this hot and dense environment of dynamically-generated baryonic resonances together with the evolution with density and temperature of the strange and open-charm meson spectral functions. We test the spectral functions for strange mesons using energy-weighted sum rules and finally discuss the implications of the properties of charm mesons on the D_{s0}(2317) and the predicted X(3700) scalar resonances.

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arXiv2009

The (K-,p) reaction on C12 at KEK

We study the (K-,p) reaction on C12 with a kaon beam of 1 GeV momentum, paying a special attention to the region of emitted protons having kinetic energy above 600 MeV, which was used to claim a deep kaon nucleus optical potential [1]. The experiment looks for fast protons emitted from the absorption of in flight kaons by nuclei, but in coincidence with at least one charged particle in the decay counters sandwiching the target. The analysis of the data is done in [1] assuming that the coincidence requirement does not change the shape of the final spectra. However our detailed calculations show that this assumption doesn't hold, and, thus, the final conclusion of this experiment is doubtful. We perform Monte Carlo simulation of this reaction. The advantage of our method with respect to Green's function method used in [1] is that it allows to account not only for quasi-elastic K- p scattering, but also for the other processes which contribute to the proton spectra. We investigated the effect of the multi-scatterings and of the K- absorptions by one and two nucleons (K- N --> pi Y and K- N N --> Y N) followed by the decay of the hyperon in pi N. We show that all these mechanisms allow us to explain reasonably well the observed spectrum with standard shallow kaon nucleus optical potential, obtained in chiral models. [1] T. Kishimoto et al., Prog. Theor. Phys. 118, 181 (2007).

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arXiv2009

Asymmetry observables in e+ e- --> pi+ pi- gamma in the phi region within a chiral unitary approach

We make a theoretical study of the charge and forward-backward pion asymmetries in the e+e- --> pi+ pi- gamma process on and off the phi resonance energy. These observables are rather sensitive to the inner details of the theoretical models to describe the reaction. In addition to the standard implementation of the initial state radiation (ISR) and the Bremsstrahlung contribution to the final state radiation (FSR), we use the techniques of the chiral unitary approach to evaluate the contribution from the mechanisms of phi decay into pi+pi-gamma. This contribution involves the implementation of final state interaction from direct chiral loops, the exchange of vector and axial-vector resonances and the final state interaction through the consideration of the meson-meson unitarized amplitudes, which where found important in a previous work describing the phi --> pi pi gamma. We find a good reproduction of the experimental data from KLOE for the forward-backward asymmetry, both at the phi peak and away from it. We also make predictions for the angular distributions of the charge asymmetry and show that this observable is very sensitive to the chiral loops involved in phi radiative decay.

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arXiv2009

Dynamically generated resonances from the vector octet-baryon decuplet interaction

We study the interaction of the octet of vector mesons with the decuplet of baryons using Lagrangians of the hidden gauge theory for vector interactions. The unitary amplitudes in coupled channels develop poles that can be associated with some known baryonic resonances, while there are predictions for new ones at the energy frontier of the experimental research. The work offers guidelines on how to search for these resonances.

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arXiv2009

Charm and hidden charm scalar mesons in the nuclear medium

We study the renormalization of the properties of low lying charm and hidden charm scalar mesons in a nuclear medium, concretely of the D_{s0}(2317) and the theoretical hidden charm state X(3700). We find that for the D_{s0}(2317), with negligible width at zero density, the width becomes about 100 MeV at normal nuclear matter density, while in the case of the X(3700) the width becomes as large as 200 MeV. We discuss the origin of this new width and trace it to reactions occurring in the nucleus, while offering a guideline for future experiments testing these changes. We also show how those medium modifications will bring valuable information on the nature of the scalar resonances and the mechanisms of the interaction of D mesons with nucleons and nuclei.

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arXiv2009

Solution to Faddeev equations with two-body experimental amplitudes as input and application to J^P=1/2^+, S=0 baryon resonances

We solve the Faddeev equations for the two meson-one baryon system $ππN$ and coupled channels using the experimental two-body $t$-matrices for the $πN$ interaction as input and unitary chiral dynamics to describe the interaction between the rest of coupled channels. In addition to the $N^*(1710)$ obtained before with the $ππN$ channel, we obtain, for $J^π=1/2^+$ and total isospin of the three-body system $I=1/2$, a resonance peak whose mass is around 2080 MeV and width of 54 MeV, while for $I=3/2$ we find a peak around 2126 MeV and 42 MeV of width. These two resonances can be identified with the $N^* (2100)$ and the $Δ(1910)$, respectively. We obtain another peak in the isospin 1/2 configuration, around 1920 MeV which can be interpreted as a resonance in the $N a_0(980)$ and $N f_0(980)$ systems.

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arXiv2009

Searching for signatures around 1920 MeV of a $N^*$ state of three hadron nature

We provide a series of arguments which support the idea that the peak seen in the $γp \to K^+ Λ$ reaction around 1920 MeV should correspond to the recently predicted state of $J^P=1/2^+$ as a bound state of $K \bar{K}N$ with a mixture of $a_0(980)N$ and $f_0(980)N$ components. At the same time we propose polarization experiments in that reaction as a further test of the prediction, as well as a study of the total cross section for $γp \to K^+ K^- p$ at energies close to threshold and of $d σ/d M_{inv}$ for invariant masses close to the two kaon threshold.

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