arXiv subjects

Eulogio Oset

Publications and source records attributed to Eulogio Oset.

At least 19 recordsLinked to original sources

arXiv2026

Theoretical description of the $D^{+} \to \bar{K}^{0} \pi^{+} \pi^{0} \pi^{0}$ reaction

We study the $D^{+} \rightarrow \bar{K}^{0} \pi^{+} \pi^{0} \pi^{0}$ reaction, which shows two clear structures: the $\bar{K}^{*0}$ and $\rho^{+}$ in the $\bar{K}^{0} \pi^{0}$ and $\pi^{+} \pi^{0}$ mass distributions, respectively. The study is done starting from the quark level with external and internal emission and hadronizing a pair of quarks to produce a vector and two pseudoscalars. We also consider another mechanism, which does not require hadronization of quark pairs: the direct production of $\bar{K}^{*0}$ and $\rho^{+}$. With the help of six unknown parameters which are fitted to the data, we are able to get a very good agreement with experimental data for the $\bar{K}^{0} \pi^{0}$ and $\pi^{+} \pi^{0}$ mass distributions and a qualitative one for the rest of mass distributions which do not show any particular structure experimentally.

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arXiv2026

Role of the $\Sigma(1430)(1/2^-)$ in the $J/\psi \to \Lambda \bar{\Lambda} \pi^0$ reaction

We study the $J/\psi \to \bar{\Lambda} \Lambda \pi^0$ reaction, an isospin violating reaction, by looking at the trios of baryon-antibaryon-pseudoscalar meson that conform a singlet of $\text{SU}(3)$ in the $u, d, s$ quarks. These terms conserve isospin; however, once the final-state interactions of meson-baryon and meson-antibaryon are taken into account, isospin is violated due to the different masses of particles within the same isospin multiplets. Since the reaction is tied to the interaction of particles, only resonances that are dynamically generated by these interactions show up in the reaction. In this sense, our approach produces the $\Sigma(1430)(1/2^-)$ state, but not the $\Sigma(1385)(3/2^+)$. Comparing with the BESIII data we observe that, within the limited statistics of the experiment, the data show a structure {around $M_{\pi\Lambda} = 1430$ MeV} that is reproduced by the theory, and no signal is seen for the $\Sigma(1385)(3/2^+)$ as the theory predicts. We call for a future update of the experiment once better statistics become available.

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arXiv2026

$KX(3872)$ interaction and correlation function

We investigate the $K X(3872)$ interaction and the corresponding correlation function, assuming the $X(3872)$ to be a molecular state of $D \bar D^*$ and $D^* \bar D$ with isospin $I=0$ and positive $C$-parity. The interaction is treated within the fixed-center approximation (FCA) to the Faddeev equations, in which the $X(3872)$ is taken as a cluster of its constituents and the kaon interacts with the $D^*$ and $D$ components. The three-body scattering amplitude is evaluated using the Fixed Center Approximation (FCA) to the Faddeev equations, improved by taking the FCA amplitude as an optical potential which is later unitarized by means of the Lippmann-Schwinger equation. We find a narrow resonant structure about 50~MeV below the $K^+ X(3872)$ threshold with a width of approximately 1~MeV, and determine the $K X(3872)$ scattering length $a = (0.39 - i\,0.00)$~fm and effective range $r_0 = (1.16 - i\,1.66)$~fm. The corresponding correlation function is evaluated and shows a clear deviation from unity at low momenta, characteristic of a strongly attractive interaction leading to a bound state. These predictions are tied to the molecular nature of the $X(3872)$ and can be measured experimentally via measurements of the $K X(3872)$ correlation function and three-body invariant mass distributions.

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arXiv2026

Identifying $\Sigma(1380)$ and $\Sigma(1430)$ in the $J/\psi \to \Lambda \pi \bar{\Sigma}$ reaction

We study the $J/\psi \to \Lambda \pi \bar{\Sigma}$ reaction by looking at the $\pi^+ \Lambda$ mass distribution at low energies, in search of signals for the low lying $\Sigma^+$ states. Apart from a clear signal of the $\Sigma(1385) (3/2^+)$ state, we find a smaller peak for the predicted $\Sigma(1430) (1/2^-)$, which has already been confirmed by the Belle Collaboration. A first analysis, considering only the $\pi\Lambda$ interaction, shows that the low energy part of the spectrum is better reproduced including contributions from the $\Sigma(1430)$ and the predicted $\Sigma(1380)(1/2^-)$ state that has been claimed before from analyses of different experiments. However, when we consider the $\pi\bar{\Sigma}$ interaction the need for the $\Sigma(1380)$ disappears.

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arXiv2026

In search for signals of the $D\bar{D}$ bound state $X(3700)$ from study of the $B^+ \to D^+ D^- K^+$, $B^0 \to D^+ D^- K^0$ and $\Lambda_b \to D^+ D^- \Lambda$ reactions

We perform a theoretical study of the $B^+ \to D^+ D^- K^+$, $B^0 \to D^+ D^- K^0$ and $\Lambda_b \to D^+ D^- \Lambda$ reactions by looking at the production mechanisms, with special emphasis in the final state interaction of the charmed mesons, which gives rise to the $X(3930)$, coupling strongly to $D_s\bar{D}_s$, and another state that we call $X(3700)$, coupling strongly to $D \bar D$ that qualifies as a $D \bar D$ bound state. The combined study of all these reactions shows that the final state interaction responsible for the production of these resonances is more important in the $B^+ \to D^+ D^- K^+$ reaction than in the $\Lambda_b \to D^+ D^- \Lambda$ one. We have taken this into account and shown that normalizing the $D^+ D^-$ mass distributions to the same value at the peak of the $\psi(3770)$ production, the two mass distributions are quite different in a range of 10 MeV above the $D^+ D^-$ threshold, with a value about an order of magnitude bigger for the $B^+ \to D^+ D^- K^+$ reaction than for the $\Lambda_b \to D^+ D^- \Lambda$ one. The $D^+D^-$ mass distribution by itself also shows an enhancement of about one order of magnitude in the presence of the $X(3700)$ with respect to a calculation where this resonance is absent. We make a call to measure these magnitudes in the coming LHCb upgrades, which would bring great support to the existence of the bound $D^+ D^-$ state.

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arXiv2026

$\Lambda(1670)$ production in the $\psi(3686) \to \Lambda \bar \Lambda \eta$ reaction

We perform a calculation of the invariant mass distributions in the $\psi(3686) \to \Lambda \bar \Lambda \eta$ reaction, where a neat peak for the excitation of the $\Lambda(1670)$ and $\bar \Lambda(1670)$ in the $\eta \Lambda$ and $\eta \bar \Lambda$ mass distributions, respectively, is observed. Our approach uses the fact that the $\psi(3686)$, a $c \bar c$ state, is a singlet of SU(3) in the $u,d,s$ quarks and constructs the two flavor structures allowed with a pseudoscalar meson, a baryon and an antibaryon. The resonance peaks come from the final state interaction of meson baryon pairs, which generate the $ \Lambda(1670)$ in our approach. With a reasonable relative weight of the two flavor structures, the only free parameter of the theory, we are able to get the three mass distributions in good agreement with experiment, giving extra support to the molecular structure of the $ \Lambda(1670)$ resonance. The agreement with data improves with an extra resonant contribution with mass around 2200 MeV, possibly accounting for some resonances.

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arXiv2026

Predicted Exotic Doubly Heavy-Strange Pentaquarks

We predict exotic doubly heavy--strange pentaquarks with minimal quark content $u\bar d sQQ'$ ($QQ'=cc,bc,bb$) within a coupled-channel unitary framework where the interaction is derived from an extension of the local hidden gauge approach to the heavy-quark sector. We obtain a robust spectrum of manifestly exotic states; two states appear in the $u\bar d scc$ sector, three in $u\bar d scb$, and four in $u\bar d sbb$. These emerge either as bound states or resonances, along with five additional virtual states manifested as threshold cusps. The binding mechanism is dominated by off-diagonal transitions among heavy-baryon--light-meson channels, while diagonal interactions are strongly suppressed. These results extend exotic hadron spectroscopy into the doubly heavy--strange sector and provide concrete targets for future experimental searches.

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arXiv2026

Interaction and correlation functions for $\pi f_1(1285)$, $\eta f_1(1285)$

We have studied the interaction of $\pi^0 (\eta) f_1(1285)$ assuming the $f_1(1285)$ to be a molecular state of $K^* \bar K - \bar K^* K$. We use a framework in which a $\pi^0 (\eta) f_1(1285)$ optical potential is obtained, which is later used as the kernel of the Lippmann-Schwinger equation, following the standard method for the interaction of particles with nuclei. The optical potential is obtained using the fixed center approximation to the Faddeev equations, where a cluster, here the $f_1(1285)$, remains unchanged during the interaction, appropriate to the situation that one has here. We have obtained the scattering matrix for this system, the scattering length and effective range, plus the correlation functions. The framework used has been previously tested in the study of the $p f_1(1285)$ interaction and has been shown to give results in agreement with the recent experimental measurement of the $p f_1(1285)$ correlation function. On the other hand, from this interaction we do not obtain clear signals for the $\pi_1(1400)$ or $\pi_1(1600)$, nor for the $\eta_1(1855)$ resonances, which in other approaches have been claimed to arise from the same dynamics. We, however, obtain a structure in the $\pi^0 f_1(1285)$ amplitude around $1500-1600{\; \rm MeV}$ and a strong cusp at the $\eta f_1(1285)$ threshold of $1833 {\; \rm MeV}$.

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arXiv2026

Role of $a_0(1710)$ in the $J/\psi\to\rho^+\rho^-\omega$ and $J/\psi\to\gamma\rho^0\omega$ reactions

We investigate the strong decay $J/\psi\to\rho^+\rho^-\omega$ and the radiative decay $J/\psi\to\gamma\rho^0\omega$, taking into account the $S$-wave $K^*\bar{K}^*$, $\rho \omega$ and $\rho \phi$ final-state interactions, which dynamically generate the scalar meson $a_0(1710)$. Our results demonstrate that a clear peak structure emerges around 1.8~GeV in the $\rho^+\omega$~($\rho^-\omega$) invariant mass distribution of the strong decay, which can be associated with the $a_0(1710)$ resonance. Similarly, a distinct peak is predicted in the $\rho^0\omega$ invariant mass distribution of the radiative decay. Our results indicate that clear signals of $a_0(1710)$ production could be observed in future measurements of these processes at BESIII, Belle II, and the planned Super Tau-Charm Facility, thereby helping to determine its mass and width more precisely.

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arXiv2026

Correlation function and bound state from the $K D_{s0}^*(2317)$ interaction

In anticipation of the new wave of ALICE experiments on particle-resonance correlation functions, we study the interaction of a kaon with the $D_{s0}^*(2317)$ resonance. Assuming the $D_{s0}^*(2317)$ to be a $DK$ molecular state in isospin $I=0$, we employ the fixed center approximation (FCA) to describe the kaon scattering off the $DK$ cluster, and implement elastic unitarity in the $K D_{s0}^*(2317)$ amplitude via an optical potential and the Lippmann-Schwinger equation. We evaluate the scattering length, effective range, and correlation function, which exhibits a shape characteristic of a strongly attractive interaction. Notably, the amplitude develops a narrow resonant peak about 40~MeV below the $K D_{s0}^*(2317)$ threshold, signaling a three-body bound state. We discuss the experimental feasibility of observing this state through the invariant mass distribution of $K D_s^+ \pi^0$, and argue that such three-body states, predicted by various theoretical approaches, offer promising targets for future experimental searches, providing valuable insights into the nature of exotic hadronic resonances.

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arXiv2026

Role of $\Xi(1690)$ in the $J/\psi\to\Xi^0\bar{\Lambda}K^0$ reaction

Motivated by the recent BESIII measurements of the $J/\psi \to \Xi^0 \bar{\Lambda}K_S^0 + c.c.$ process, we investigate this reaction by considering the contributions from the $\Xi(1690)$, $\Lambda(1890)$ and $\Lambda(1830)$ resonances. The $\Xi(1690)$ state is dynamically generated from the $S$-wave pseudoscalar meson-octet baryon interactions within the chiral unitary approach. Our theoretical model provides a good description of the $\bar{\Lambda}K^0$, $\Xi^0 K^0$, and $\bar{\Lambda}\Xi^0$ invariant mass distributions. The results indicate that the $\Xi(1690)$ resonance, which was neglected in the experimental analysis by BESIII, plays a crucial role in this process. Furthermore, we evaluate the theoretical uncertainties of our model using the parametric bootstrap method. Future high-precision measurements of this process will further help to elucidate the properties of the $\Xi(1690)$, $\Lambda(1890)$ and $\Lambda(1830)$ states.

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arXiv2026

Scattering observables and correlation function for $p ~f_1(1285)$ revisited

In view of the recent theoretical developments in the fixed center approximation for the scattering of a particle with a a two-body cluster, implementing elastic unitarity on the standard fixed center formalism, and the imminent availability of ALICE data on the correlation function of the $p~f_1(1285)$ system, we update the results of a previous work for this correlation function and the low-energy scattering observables. The new results show appreciable changes in some observables and should provide valuable input for comparison with the forthcoming experimental data. Such a comparison is expected to yield relevant information on the nature of the axial-vector meson states.

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arXiv2026

Scattering data and correlation function for the $K f_1(1285)$ interaction

We study the interaction of a kaon with the $f_1(1285)$ resonance, assuming that the $f_1(1285)$ is a molecular state generated by the $K \bar K^*, \bar K K^*$ interaction, evaluating the scattering amplitude, the scattering length and effective range of the $K f_1$ system. The scattering amplitude develops a resonant structure approximately \R{$56$ MeV} below the $K f_1$ threshold, with a width of around \R{$123$ MeV} MeV. The corresponding correlation function has the distinctive shape of a system with a bound state close to threshold. We also show that the interaction of the $K f_1$ system differs significantly from the one obtained assuming that the $f_1(1285)$ is an \R{ordinary, non-molecular,} particle. This provides motivation to continue the search for these observables, already initiated by the measurement of the $p f_1(1285)$ correlation function by the ALICE collaboration.

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arXiv2026

The $\Omega(2380)$ as a partner of the $\Omega(2012)$

We present a study of the $\Omega(2380)$ resonance and show that it is consistent with a dynamically generated state arising from the $\bar{K}^*\Xi^*$, $\omega\Omega$, and $\phi\Omega$ interactions. In this picture, the $\Omega(2380)$ is analogous to the $\Omega(2012)$, which is generated from the $\bar{K}\Xi^*$ and $\eta\Omega$ channels. The resulting mass, total width, and partial decay widths into the $\bar{K}\Xi^*$ and $\bar{K}^*\Xi$ channels are compatible with the available experimental data. We also discuss possible experimental observables that could provide further insight into the nature of this state.

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arXiv2026

Searching for a $P_{cs}(4200)$ state in the $\Lambda_b\to\phi\eta_c\Lambda$ reaction

We propose the $\Lambda_b\to\phi \eta_c \Lambda$ reaction to observe a $P_{cs}$ state around $4200$ MeV, predicted at lower masses than expected from comparison with the $P_c$ states, stemming as a consequence of the important role played by coupled channels in the $P_{cs}$ case, which does not appear in the $P_c$ case. That state decays to $\eta_c \Lambda$ with a width of about $200$ keV. The reaction is related to $\Lambda_b^0\to\phi D_s^- \Lambda_c^+$, which has already been observed. We predict a branching fraction for $\Lambda_b\to\phi P_{cs}(4200)$; $P_{cs}\to\eta_c \Lambda$ of the order of $10^{-5}$, which is within present capabilities of the LHCb collaboration. The observation of this state would bring valuable light on the nature of the $P_c$ and $P_{cs}$ states and the role played by coupled channels in hadron structure and hadron reactions.

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arXiv2025

The $B^{+(0)} \to \bar D^{0(-)} D^{}_{s0}(2317)^+$ decays and the molecular structure of $D^_{s0}(2317)$

We have conducted a study of the $B^{+(0)} \to \bar D^{0(-)} D^{*}_{s0}(2317)^+$ reactions from the perspective that the $D^*_{s0}(2317)$ resonance is a molecular state of the $DK$ and $D_s \eta$ components. We have followed a method to evaluate the branching fractions obtaining information from the experimental data on the $B^+\to \bar D^0 K^+ D^0$, $B^+\to \bar D^0 K^0 D^+$, $B^0 \to D^- K^+ D^0$, $B^0 \to D^- K^0 D^+$ reactions, which have the $D^0 K^+$ and $D^+ K^0$ pairs in the final state. The approach concentrates the dynamics of the weak process in the branching ratios of these reactions and pays attention to the propagation of the $DK$ components and their strong interaction to form the $D^*_{s0}(2317)$ resonance. By means of two free parameters, we are able to describe these six rates, showing consistency with the molecular picture of the $D^*_{s0}(2317)$ state.

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arXiv2025

$a_0(980)$ production, triangle singularity, and non-$\phi$ background in the $J/\psi \to \phi \eta \pi^0$ reaction

We study the $J/\psi\to\phi\eta\pi^{0}$ 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 $\pi^0\eta$ mass distributions, with the typical narrow width observed in isospin violating processes; 2) The origin of two peaks in the $\phi\pi^{0}$ mass distributions that were branded as ``non $\phi$" contribution in the experimental analysis; 3) The existence of two triangle mechanisms developing a triangle sigularity at the same energy where the ``non $\phi$" 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 $\phi$ looking at $K^+K^-$ in a narrow window of invariant mass around the $\phi$ mass. We suggest that these triangle singularities could be observed with other methods to identify the $\phi$.

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arXiv2025

The $D_{s0}^(2317)^+$ decay to $D_s^+\pi^0$ and $D_s^{+}\gamma$

We study the strong decay of $D_{s0}^*(2317)^+$ to $D_s^+ \pi^0$ considering the coupled channels of $D^0 K^+, D^+ K^0, D_s^+ \eta$ and $D_s^+ \pi^0$ within a picture for the interaction based on the local hidden gauge approach. We also address the problem of the radiative decay to $D_s^{*+} \gamma$, 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 $\pi^0-\eta$ 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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