arXiv subjects

Eulogio Oset

Publications and source records attributed to Eulogio Oset.

At least 37 records · Page 2Linked to original sources

arXiv2026

The $D_{s0}^(2317)^+$ decay to $D_s^+π^0$ and $D_s^{+}γ$

We study the strong decay of $D_{s0}^*(2317)^+$ to $D_s^+ π^0$ considering the coupled channels of $D^0 K^+, D^+ K^0, D_s^+ η$ and $D_s^+ π^0$ within a picture for the interaction based on the local hidden gauge approach. We also address the problem of the radiative decay to $D_s^{*+} γ$, using the same information obtained from the molecular picture. We obtain a strong width of the $D_{s0}^*(2317)^+$ of about $77 \,\rm keV$ from coupled channels interaction and a radiative decay of about $1.7 \,\rm keV$. We also show that the extra consideration of $π^0-η$ mixing can double the strong decay width to values around $140 \,\rm keV$. The anomalous terms for the radiative decay are considered for the first time, but they are found negligible. We make a thorough discussion of this and other results to the light of the recent measurement of Belle for the ratio of these two decay modes, and make a call for the precise measurement of the two decay widths independently to clarify the present situation concerning the nature of the $D_{s0}^*(2317)^+$ state.

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arXiv2026

$a_0(980)$ production, triangle singularity, and non-$ϕ$ background in the $J/ψ\to ϕηπ^0$ reaction

We study the $J/ψ\toϕηπ^{0}$ reaction measured recently by the BESIII collaboration with high precision, paying attention to three important aspects: 1) The production of the $a_0(980)$ in the $π^0η$ mass distributions, with the typical narrow width observed in isospin violating processes; 2) The origin of two peaks in the $ϕπ^{0}$ mass distributions that were branded as ``non $ϕ$" contribution in the experimental analysis; 3) The existence of two triangle mechanisms developing a triangle sigularity at the same energy where the ``non $ϕ$" contribution peaks in the experiment. However, we also show that the strength of these peaks is very small relative to the observed ones, a feature which is tied to the experimental technique used to identify the $ϕ$ looking at $K^+K^-$ in a narrow window of invariant mass around the $ϕ$ mass. We suggest that these triangle singularities could be observed with other methods to identify the $ϕ$.

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arXiv2026

Superexotic $K^{+}D^{+}K^{*+}$ bound state

We study a system made from $K^{*+}D^{*+}K^{*+}$ with charge $3$, isospin $I=3/2$, spin $J=3$, and a quark content of $c\bar d \bar s u \bar s u$, which make it highly exotic relative to the standard $q\bar q$ structure of mesons. The interaction of the three body system is obtained starting from a cluster of $K^{*+}D^{*+}$ in $I=1$ and $J=2$, that in different works has been found bound, and adding to it an extra $K^{*+}$ with spin aligned with those of the vectors of the cluster. We find that the $K^* K^*$ interaction in $I=1$ and $J=2$ is repulsive, but its strength is small compared to that of $K^{*+}D^{*+}$ in $I=1$ and $J=2$, such that we find a three body state bound by about $100 \, \rm MeV$ with respect to the mass of a $K^{*+}$ and the $K^{*+} D^{*+}$ cluster. The width of the state, of about $10\, \rm MeV$, is much smaller than the binding, which facilitates its observation. We suggest to find that state by measuring the invariant mass of $K D K^*$, something feasible in present experimental facilities.

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arXiv2025

Correlation function for the $n \bar{D}_{s0}^*(2317)$ interaction and the issue of elastic unitarity

We study the interaction of a neutron with the $\bar D_{s0}^*(2317)$ resonance and look at the amplitude below threshold and close above threshold. The study is done from the perspective that the $D_{s0}^*(2317)$ resonance is a molecular state of $DK$ in $I=0$. To study this interaction, we use the Fixed Center Approximation to Faddeev equations that considers the $DK$ molecule as the cluster and the neutron as the external particle. We improve the Fixed Center approach to implement elastic unitarity around threshold, which is needed to obtain scattering parameters and to evaluate the $n \bar D_{s0}^*(2317)$ correlation function that we determine here. One interesting result of the study is the appearance of a resonant state below threshold with a binding of about 130 MeV and a width of about 80 MeV, which we suggest to look at in reactions measuring the invariant mass of $πΣ\bar D$. The ALICE collaboration has initiated studies of this type, by looking at the $p f_1(1285)$ correlation function, and we can only encourage work in this direction which should provide much valuable information on the nature of many resonant states.

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arXiv2025

On the $π^+π^-$ and $D^+_sπ^{\pm}$ mass spectra in the $D_{s1}(2536) \to D^+_sπ^+π^-$ decays

We have carried out an evaluation of the $π^+ π^-$ and $D_s^+ π^+$ mass distributions in the $D_{s1}(2536)$ decay to $D_s^+ π^+ π^-$, from the perspective that the $D_{s1}(2536)$ is a molecular state, mostly made from $K^*D$ in $I=0$. We are able to obtain, not only the mass distributions, but the branching ratio of this decay. The shape of the mass distributions differ appreciably from those of the analogous reaction $D_{s1}(2460)\to D_s^+ π^+ π^-$, which has been measured by the LHCb collaboration and analyzed theoretically from the perspective that the $D_{s1}(2460)$ is a molecular state of $D^*K$, showing a good agreement with the data. In spite of the analogy with the $D_{s1}(2460)$ decay, the dynamical differences in the decay mechanism are important, since now the $f_0(500)$ resonance is not generated, while it was the dominant mechanism in the $D_{s1}(2460)\to D_s^+ π^+ π^-$ decay. Nonetheless, we find striking differences in the mass distributions compared with phase space as a consequence of the decay mechanism. The branching ratio obtained is an order of magnitude bigger than the one of the $D_{s1}(2460)\to D_s^+ π^+ π^-$ reaction, mostly due to the larger available phase space. We also show that the shape of the distributions obtained from the molecular picture are quite different from those obtained based on a $q\bar{q}$ picture. We conclude that measuring the shape of the mass distributions and the total strength of the decay mode, should be very valuable to learn about the structure of the $D_{s1}(2536)$.

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arXiv2025

The role of the $f_0(1710)$ and $a_0(1710)$ resonances in the $D^0 \to ρ^0 ϕ$, $ωϕ$ decays

We study the $D^0 \to ρ^0 ϕ$, $ωϕ$ decays which proceed in a direct mode via internal emission with equal rates. Yet, the experimental branching ratio for the $ρ^0 ϕ$ mode is twice as big as that for the $ωϕ$ mode. We find a natural explanation based on the extra indirect mechanism where $K^{*+} K^{*-}$ is produced via external emission and that channel undergoes final state interaction with other vector--vector channels to lead to the $ρ^0 ϕ$, $ωϕ$ final states, with transition amplitudes dominated by the $a_0(1710)$ resonance, recently discovered, and $f_0(1710)$ respectively. The large coupling of the $a_0(1710)$ to the $ρ^0 ϕ$ channel is mostly responsible for this large ratio of the production rates.

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arXiv2025

$a_0(980)$ and $f_0(980)$ excitation in the $D^+ \to π^+ ηη$ decay

We have made a thorough study of the $D^+ \to π^+ ηη$ reaction, recently measured by the BESIII collaboration, which shows an abnormal strength at high invariant masses in the $πη$ mass distribution. We studied in detail the triangle mechanism and the $f_0(1370)$ excitation modes that have been suggested to explain this abnormal feature, and concluded that they are too small to have any important role in the solution to that problem. We have also studied other possible solutions evaluating the contribution of excitations of other $f_0$, $a_0$ and $f_2$ resonances and reached the same conclusion. Unexpectedly, the solution to the problem is found considering the $f_0(980)$ excitation, with the $f_0(980)$ decaying to two $η$, which is tied to the $a_0(980)$ production, and well under control. At the same time, the consideration of the $f_0(980)$ excitation solves another non reported problem, which is the $ηη$ mass distribution that comes when only the $a_0(980)$ resonance is allowed to be excited, which produces a large deficiency at low invariant masses compared with experiment.

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arXiv2025

Revisiting the $Λ_c^+\to Ληπ^+$ and the roles of intermediate resonances

In this paper, we first review the theoretical and experimental studies of the process $Λ_c^+ \to π^+ ηΛ$. Motivated by the recent BESIII and Belle measurements, we have conducted a theoretical study of the process $Λ_c^+ \to π^+ ηΛ$, where the $a_0(980)$ and $Λ(1670)$ resonances are dynamically generated from the $S$-wave meson meson and meson baryon interaction, respectively. Our results give a reasonable description of the invariant mass distributions, which implies that the spin flip contribution in the $Σ(1385)$ excitation plays an important role.

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arXiv2025

Revisiting the $Λ_c^+\rightarrow\bar{K}^0ηp$ reaction: the role of $N^(1535),~ N^(1650)$ and $Σ(1620)$

We perform a theoretical study of the weak decay $Λ_c^+ \rightarrow \bar{K}^0 ηp$ using a coupled-channel chiral unitary approach that incorporates both pseudoscalar-baryon and vector-baryon interactions. Our framework includes contributions from both internal and external weak emission mechanisms, as well as strong final state interactions. We assume that the $N^*(1535)$ and $N^*(1650)$ resonances are dynamically generated through meson-baryon scattering and they appear as distinct structures in the $ηp$ invariant mass distributions. {A clear peak also appears in the $\bar{K}^0 p$ invariant mass distribution around 1620~MeV, associated with the dynamically generated $Σ(1620)$ resonance.} Notably, this work provides the first theoretical description of the simultaneous observation of these two related $N^*$ resonances in the same meson-baryon final state. Our results highlight the crucial role of final state interaction and the interplay between different weak decay topologies in shaping the resonance patterns. These findings offer new insights into the nature of nucleon excitations and support the interpretation of $N^*(1535)$ and $N^*(1650)$ as dynamically generated states. {Moreover, the identification of the $Σ(1620)$ further supports the picture of hadronic molecular structures emerging from meson-baryon interactions in the non-perturbative QCD regime.}

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arXiv2025

Exotic multistrange-anticharm baryon systems

We study exotic baryon systems composed of anticharmed mesons and strange baryons using the extended local hidden gauge approach. By solving the coupled-channel Bethe-Salpeter equation with interaction kernels from vector meson exchange, we explore the formation of hadronic molecular states in sectors with strangeness $S = -1$, $-2$, $-3$ and $-4$. {We systematically consider all possible isospin configurations and include both octet and decuplet baryons in the coupled-channel systems.} \textcolor{black}{Our results indicate that attractive interactions in $S=-1,-2$ can dynamically generate bound states, while systems with $S=-3,-4$ have repulsive interactions and do not support molecular formation.} We also investigate vector-baryon systems with $\bar{D}^*$ and $\bar{D}_s^*$ mesons, finding similar but more deeply bound states. The results show that bound exotic states are more likely when one or two strange quarks are present. {To assess the robustness of our predictions, we perform an uncertainty analysis by varying the cutoff parameter $ q_{\text{max}} $, which affects the loop function regularization. The variations lead to moderate shifts in the pole positions, confirming the qualitative stability of the molecular states.} These results highlight the strangeness dependence of the molecular formation mechanism and provide theoretical predictions that can guide future experimental searches for exotic multistrange-anticharm baryon systems.

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arXiv2025

Molecular states with bottom mesons and multistrange baryons systems

We investigate molecular states formed by bottom mesons and multistrange baryons from both octet and decuplet flavor representations, using the local hidden gauge approach combined with coupled-channel Bethe-Salpeter equations. Focusing on strangeness sectors $S = -1$ to $-4$, we predict several bound states in the $S=-1, I=1/2,~3/2$ and $S=-2, I=0$ sectors. No bound states are found in other isospin channels, where the interaction is repulsive, nor in higher strangeness sectors. The binding energies are analyzed under different values of the cutoff regularization parameters, providing estimates of theoretical uncertainties. This study provides concrete predictions to support future experimental investigations and improve understanding of heavy-flavor multistrange exotic hadrons.

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arXiv2025

Final state interaction in the $Λ_b\to D^+D^- Λ,~D^0D_s^- p,~D_s^+D_s^-Λ$ reactions

We study the three-body decays $Λ_b \to D^+ D^- Λ,~D^0D_s^- p,~D_s^+D_s^-Λ$, considering both internal and external emission mechanisms that produce various meson-baryon final states. Using a unitarized coupled-channel approach based on the local hidden gauge formalism, we analyze final state interactions in the exotic anticharm systems with strangeness $S=-1$ and $S=-2$. Significant threshold enhancements appear in both pseudoscalar and vector meson-baryon channels, indicating strong final state interactions and the possible formation of molecular exotic states below threshold. These features remain stable under variations of model parameters. Our results provide valuable insights into heavy hadron decay dynamics and offer theoretical guidance for future experimental searches of open-charm strange exotic hadrons.

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arXiv2025

Determination of the binding and $DK$ probability of the $D^{*}_{s0}(2317)$ from the $(\bar{D}\bar K)^-$ mass distributions in $Λ_{b}\to Λ_{c} (\bar{D}\bar K)^-$ decays

We study the $Λ_{b}\toΛ_{c}\bar{D}^{0}K^{-}$ and $Λ_{b}\to Λ_{c}D^{-}\bar{K}^{0}$ decays which proceed via a Cabibbo and $N_c$ favored process of external emission, and we determine the $\bar{D}^{0}K^{-}$ and $D^{-}\bar{K}^{0}$ mass distributions close to the $\bar{D} \bar{K}$ threshold. For this, we use the tree level contribution plus the rescattering of the meson-meson components, using the extension of the local hidden gauge approach to the charm sector that produces the $D^*_{s0}(2317)$ resonance. We observe a large enhancement of the mass distributions close to threshold due to the presence of this resonance below threshold. Next we undertake the inverse problem of extracting the maximum information on the interaction of the $\bar{D} \bar{K}$ channels from these distributions, and using the resampling method we find that from these data one can obtain precise values of the scattering lengths and effective ranges, the existence of an $I=0$ bound state with a precision of about $4 \;\rm MeV$ in the mass, plus the $\bar{D} \bar{K}$ molecular probability of this state with reasonable precision. Given the fact that the $Λ_{b}\toΛ_{c}\bar{D}^{0}K^{-}$ decay is already measured by the LHCb collaboration, it is expected that in the next runs with more statistics of the decay, these mass distributions can be measured with precision and the method proposed here can be used to determine the nature of the $D^*_{s0}(2317)$, which is still an issue of debate.

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arXiv2025

Correlation function for the $p ~f_1(1285)$ interaction

We have addressed here the problem of calculating the correlation function of a stable particle with a resonance, in particular one resonance that qualifies as a molecular state of two components. The formalism used requires to evaluate the scattering matrix of the stable particle with the molecule, a nuclear problem which we address by means of the fixed center approximation. We have applied the method to the interaction of a proton with the $f_1(1285)$ resonance, presently under investigation by the ALICE collaboration, where the $f_1(1285)$ is taken as a $K^*\bar{K}-\bar{K}^*K$ molecule. We find that the $p ~ f_1(1285)$ interaction develops a resonance state below the $p ~ f_1(1285)$ threshold, which leads to a depletion in the $p ~ f_1(1285)$ correlation function for small values of the proton momentum. The discussion presented shows that these type of studies can provide much information on the nature of some resonances and the existence of three-body bound states involving mesons and baryons.

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arXiv2025

The $Λ_c^+\toΛπ^+π^+π^-$ reaction, and a triangle singularity producing the $Σ^*(1430)$ state

We study the decay $Λ_c^+ \to Λπ^+ π^+ π^-$, focusing on the production of the $Σ^*(1430)$ resonance observed by the Belle Collaboration. Interpreted as a dynamically generated state from meson-baryon interactions in the chiral unitary approach, the $Σ^*(1430)$ signal is shown to be enhanced by a triangle singularity involving intermediate $K^{*-}$, $p$, and $\bar K^0$ states. This mechanism leads to a sharp peak near 1434 MeV in the $π^+ Λ$ invariant mass distribution, in agreement with the experimental observations, and predicts a secondary peak around 1875 MeV in the $π^- Σ^*(1430)$ spectrum tied to the triangle singularity. We also estimate the branching ratio of $Λ_c^+ \to π^+ π^- Σ^*(1430)$ to be about $3.5 \times 10^{-4}$. The results for the branching ratio and the $π^- Σ^*(1430)$ mass distributions are predictions of the theoretical approach, which could be tested with reanalysis of existing data.

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arXiv2025

Testing the nature of the $Σ^*(1430)$

We study the feasibility of having the $Σ^*(1430)$ state, predicted within the chiral unitary approach and recently reported by the Belle Collaboration, as corresponding to a state of non-molecular nature. Starting from this assumption, since the state is observed in the $πΛ$ channel, we allow the coupling to this state and relate the coupling to $\bar K N$ and $πΣ$ using $SU(3)$ symmetry arguments. We find that it is possible to have such a state with negligible coupling to the molecular components with a bare mass of the state very close to the physical mass of the $Σ^*(1430)$. Yet, this has consequences on other observables, since the width obtained is extremely small and incompatible with the Belle observations, and it leads to abnormally large values of the $\bar K N$ effective range. Conversely, such mismatches do not appear for large values of the bare mass of the state, but in this case we observe that the state develops large molecular components. While one can rule out a largely non-molecular nature for this state, its properties and detailed nature will need further experimental developments which one can anticipate will be coming in the near future.

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arXiv2025

Determination of the $K^+\bar{K}^0$ scattering length and effective range from the $D^+\to\bar{K}^0π^+η$ reaction

We study the scattering parameters of the $K^+\bar{K}^0$ system through the analysis of the $D^+\to\bar{K}^0π^+η$ reaction, aiming at determining the scattering length $a$ and effective range $r_0$ of the $K^+\bar{K}^0$ interaction. These parameters are extracted by analyzing and fitting the mass distributions of the pairs in the final $\bar{K}^0π^+η$ state. To ensure the reliability of the results, we apply resampling techniques to evaluate statistical uncertainties and improve the precision of the scattering parameters. The obtained results are compared with previous theoretical predictions and experimental data, providing new insights into the $K^+\bar{K}^0$ interaction at low energies.

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arXiv2025

Searching for the $2^+$ partner of the $T_{cs0}(2870)$ in the $B^- \to D^- D^0 K^0_S$ reaction

We study the $B^- \to D^- D^0 K^0_S$ reaction, recently analyzed by the LHCb collaboration, where a clear signal for the exotic $T_{cs0}(2870)$ state has been reported. We call the attention to a small peak in the $D^0 K^0_S$ mass distribution that could correspond to a state of the same nature as the $T_{cs0}(2870)$ ($D^* \bar K^*$ nature in the molecular picture) but with $J^P= 2^+$. In order to magnify the signal for the state, we calculate the moments of the angle-mass distribution, which are linear in the resonance signal, rather than quadratic for the angle integrated mass distribution. We find spectra for the moments with a strength far bigger than that for the angle integrated mass distribution, which should encourage the evaluation of these moments from the present measurements of the reaction.

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