arXiv subjects

E. Oset

Publications and source records attributed to E. Oset.

At least 19 recordsLinked to original sources

arXiv2026

Meson-baryon final-state interactions in the $ψ(3686)\to pK^-K_S^0\barΞ^0$ decay

We study the decay $ψ(3686)\to p K^- \bar K^0 \barΞ^0$, treating the $ψ(3686)$ as a $c\bar c$ state and therefore as a singlet under SU(3) transformations in the light-quark sector. We consider all possible combinations of a baryon, an antibaryon, and two pseudoscalar mesons that form an SU(3) singlet, retaining the terms that can lead to the $p K^- \bar K^0 \barΞ^0$ final state through $S$-wave final-state interactions. Three independent SU(3)-singlet structures are identified and assigned different weights. We also include the contribution of the $Λ(1520)$ in the meson-baryon $D$-wave. A fit to the data provides a good description of all six invariant-mass distributions. In addition to the $Λ(1520)$ contribution, we find a small contribution from the $Λ(1670)$ in the $K^-p$ invariant-mass distribution, generated by final-state interactions, and a contribution from the $Σ(1430)$, which produces a significant distortion of the $\bar K^0p$ invariant-mass distribution relative to phase space. This study demonstrates the value of investigating charmonium decays into a baryon-antibaryon pair and two pseudoscalar mesons, complementing the more commonly studied decays into a baryon-antibaryon pair and a single pseudoscalar meson.

hep-ph↗

arXiv2026

A glueball puzzle explained in terms of $ϕh_1(1380)$ dynamics: Aka $X(2370)$

We study the interaction of $ϕ$ with $h_1(1380)$, considering the latter as a $K^*\bar K$ molecular state, and find the generation of a state with the same quantum numbers, together with a mass and width compatible with the experimental results, as those of $X(2370)$, recently advocated as a candidate for a glueball. Within our description, the suppressed decay modes of $X(2370)$ to $γω$, $ωϕ$ and $K^*\bar K$, reported in the experimental paper as clues to its glueball nature, are naturally explained. Conversely, the non $K^* \bar K$ decay to $K \bar K π$ (the latter being the invariant mass where the resonance is observed) is shown to be largely enhanced due to the combination of a triangle singularity and the presence of $K(1630)$ in the $ρϕ\to \bar K$ vertex involved in the triangle loop.

hep-ph↗

arXiv2026

$ \bar K^0 d $ Bound State and Correlation Function

We study the $\bar{K}^0d$ system using a new formulation of the fixed-center approximation that preserves elastic unitarity. The resulting scattering amplitude predicts a bound state below threshold, which can be interpreted as a $Λ(1380)N$ configuration complementary to the $K^-pp$ state associated with the higher $Λ(1405)$ pole. The interaction is attractive, with scattering parameters of the same order as recent $K^-d$ determinations. We further calculate the $\bar{K}^0d$ correlation function, which exhibits a characteristic structure associated with the bound state and provides a Coulomb-free observable that can be tested in future ALICE measurements. Results obtained with two different $\bar{K}N$ models are very similar, indicating the robustness of the predictions against the choice of the underlying interaction.

hep-ph↗

arXiv2026

Exotic states with charm and/or strangeness

In this talk, I will discuss the properties of several exotic states with charm and/or strangeness. These states can be interpreted either as being generated from two- or three-hadron dynamics. In particular, I will focus on $D_1(2420)$ and some predictions of three-body states obtained from $n\bar

hep-ph↗

arXiv2026

Study of the $J/ψ\to Λ\barΣ^0η$ reaction

We study the isospin violating $J/ψ\to Λ\bar Σ^0 η$ reaction, recently measured by the BESIII collaboration, by looking at the dominant terms with $\bar Σ^0$ and a pair of pseudoscalar-baryon particles that form together an SU(3) singlet and can thus couple to the $J/ψ$. Next we allow these pairs to undergo final state interaction to produce the final $ηΛ$. We find that the relevant original channels are $\bar K N$ and $K Ξ$, and the non cancelation of terms involving charged and neutral particles, because of their different masses, is responsible for the reaction. With that mechanism we find a good agreement with the three experimental mass distributions.

hep-ph↗

arXiv2025

Study of hidden-charm, doubly-strange pentaquarks in $Λ_b\to J/ψΞ^- K^+$ and $Ξ_b\to J/ψΞ^- π^+$

Hidden-charm pentaquark states with double strangeness, $P_{css}$, have been predicted within the framework of unitary coupled-channel dynamics. In this work, we theoretically investigate the potential to observe these states in the decays $Λ_b\to J/ψΞ^-K^+$ and $Ξ_b\to J/ψΞ^-π^+$. In this framework, these pentaquark configurations couple strongly to the $J/ψΞ$ channel, as well as to other vector-baryon channels with the $\bar c c s s n$ flavor structure, making these decay modes promising for their observation through the corresponding invariant-mass distributions. Our analysis begins with the identification of the dominant weak decay mechanisms, followed by hadronization into meson-baryon channels, connected through flavor symmetry. Final-state interactions are then incorporated to dynamically generate the full amplitude, accounting for the formation of the pentaquark states. We compare our results with recent LHCb measurements of the $J/ψΞ^-$ mass distribution and find that, given the predicted pentaquark width of about 10 MeV in this channel, the state is too narrow to be resolved with the current experimental resolution, but it would become visible with significantly improved mass precision.

hep-ph↗

arXiv2025

Correlation functions for $n\,\bar{D}_{s1}(2460)$ and $n\,\bar{D}_{s1}(2536)$

We study the interaction of the $n \bar {D}_{s1}(2460)$ and $n \bar {D}_{s1}(2536)$ systems from the perspective that the $D_{s1}(2460)$ and $D_{s1}(2536)$ states are molecular states of $K D^*$ and $K^*D$, respectively. We use an improved version of the fixed center approximation to the Faddeev equations which fulfills exact elastic unitarity at the threshold of the systems. We predict the existence of resonant states below threshold and also determine the scattering length, effective range and correlation functions of these systems, showing that the results contain important information to test the assumed molecular nature of the two $D_{s1}$ states.

hep-ph↗

arXiv2025

Off-shell ambiguities in correlation functions: strategies to minimize them

We face here the problem of uncertainties in correlation functions due to the freedom in the off-shell dependence of the wave functions, or equivalently, off-shell ambiguities in the scattering matrices. We make the study for the case of meson baryon interaction, choosing the $KΛ$, $K Σ$, $ηN$ coupled channels, which are related to the $N^*(1535)$ resonance. We find that using realistic interactions based on chiral dynamics the uncertainties are small, of the order of $2-3$~\%, but could be much bigger if other methods are used. However, our study shows the way to optimally overcome these uncertainties in the analysis of correlation functions, and we provide a series of recommendations for any general analysis.

hep-ph↗

arXiv2025

The $D_{s1}(2460) \to D_s π^+ π^- $ decay from a $D_{s1}$ molecular perspective

We conduct a theoretical study of the $ D_{s1}(2460) \to D_s π^+ π^- $ decay from the perspective that the $D_{s1}$ is a molecular state, built mostly from the $D^* K$ and $D_s^* η$ components. The $D^*$ and $D_s^*$ mesons are allowed to decay into two pseudoscalars, with one of them merging with the other pseudoscalar that forms the $D_{s1}$ state, ultimately leading to the $π^+ π^- D_s$ final state. This results in a triangle diagram mechanism where all theoretical ingredients are well-known, leading to a free parameter framework. We evaluate the mass distributions of particle pairs and find good agreement with the experimental distributions of a recent LHCb experiment, providing strong support to the molecular picture of the $D_{s1}(2460)$ state. We also discuss the role played by the scalar mesons $f_0(500)$ and $f_0(980)$, at odds with the interpretation of the experimental analysis.

hep-ph↗

arXiv2024

Femtoscopy correlation functions and mass distributions from production experiments

We discuss the relation between the Koonin-Pratt femtoscopic correlation function (CF) and invariant mass distributions from production experiments. We show that the equivalence is total for a zero source-size and that a Gaussian finite-size source provides a form-factor for the virtual production of the particles. Motivated by this remarkable relationship, we study an alternative method to the Koonin-Pratt formula, which connects the evaluation of the CF directly with the production mechanisms. The differences arise mostly from the $T$-matrix quadratic terms and increase with the source size. We study the case of the $D^0 D^{\ast +}$ and $D^+ D^{\ast 0}$ correlation functions of interest to unravel the dynamics of the exotic $T_ {cc}(3875)^+$, and find that these differences become quite sizable already for 1 fm sources. We nevertheless conclude that the lack of coherence in high-multiplicity-event reactions and in the creation of the fire-ball source that emits the hadrons certainly make much more realistic the formalism based on the Koonin-Pratt equation. We finally derive an improved Lednicky-Lyuboshits (LL) approach, which implements a Lorentz ultraviolet regulator that corrects the pathological behaviour of the LL CF in the punctual source-size limit.

hep-ph↗

arXiv2024

One or two poles for the $Ξ(1820)$?

In this talk, we present a new interpretation for the recently observed $Ξ(1820)$ resonance. We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the $Ξ(1820)$ resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the $K^- Λ$ mass distribution in the $ψ(3686)$ decay to $K^- Λ\barΞ^+ $, which demands a width much larger than the average of the PDG, and show how the consideration of the two $Ξ(1820)$ states provides a natural explanation to this apparent contradiction.

hep-ph↗

arXiv2024

Production of pentaquarks with hidden charm and double strangeness in $Ξ_b$ and $Ω_b$ decays

Recently, several pentaquark states $P_{css}$, with global flavor $\bar c c s s n$, have been predicted within a theoretical framework based on unitary coupled channels. We study theoretically the feasibility to observe the $P_{css}$ with $I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$ in the decays $Ξ_b^0\to ηη_c Ξ^0$ and $Ω_b^-\to K^- η_c Ξ^0$. Indeed, within the model, the $η_c Ξ^0$ channel is the lowest mass pseudoscalar-baryon channel to which this pentaquark state couples, thus we can expect to observe its signal in the $η_c Ξ^0$ invariant mass distribution of the mentioned decays. We identify the dominant weak decay processes and then implement the hadronization into the different meson-baryon channels in the final state, linked by flavor symmetry. The dominant meson-baryon final state interaction is then implemented to generate the full amplitude, implicitly accounting for the dynamical emergence of the pentaquark states. We obtain a clear Breit-Wigner-like resonant signal in the spectrum of the $Ω_b^-$ decay, exceeding that in the $Ξ_b^0$ decay by two to three orders of magnitude. In the case of the latter decay, the resonant state would manifest as a significant dip in the spectrum. We study the feasibility of searching for these $b$-hadron decay modes and analysing their resonant components using the current and future data samples from the LHCb experiment.

hep-ph↗

arXiv2024

Searching for the two poles of the $Ξ(1820)$ in the $ψ(3686) \to \barΞ^+ \bar{K}^0 Σ^{*-}(π^- Λ)$ decay

We propose the reaction $ψ(3686) \to \barΞ^+ \bar{K}^0 Σ^{*-}$, with the $Σ^{*-}$ decaying to $π^- Λ$ in order to show evidence for the existence of two $Ξ(1820)$ states, one around $1824$ MeV and narrow, and another one around $1875$ MeV and wide. The phase space for $\bar{K}^0 Σ^{*-}$ production reduces the effect of the lower mass resonance, magnifying the effect of the higher mass resonance that shows clearly over the phase space. The estimated rate of the production is bigger than the one of the $ψ(3686) \to \barΞ^+ K^- Λ$ reaction, where a clear peak for $Ξ(1820)$ was observed by the BESIII collaboration, what makes the Beijing facility ideal to carry out the reaction proposed.

hep-ph↗

arXiv2024

Triangle singularity in the $J/ψ\to ϕπ^+ a_0^-(π^- η),\; ϕπ^- a_0^+(π^+ η)$ decays

We study the $J/ψ\to ϕπ^+ a_0(980)^- (a_0^- \to π^- η)$ decay, evaluating the double mass distribution in terms of the $π^- η$ and $π^+ a^-_0$ invariant masses. We show that the $π^- η$ mass distribution exhibits the typical cusp structure of the $a_0(980)$ seen in recent high statistics experiments, and the $π^+ a^-_0$ spectrum shows clearly a peak around $M_{\rm inv}(π^+ a^-_0)=1420 \,{\rm MeV}$, corresponding to a triangle singularity. When integrating over the two invariant masses we find a branching ratio for this decay of the order of $10^{-5}$, which is easily accessible in present laboratories. We also call attention to the fact that the signal obtained is compatible with a bump experimentally observed in the $ηπ^+π^-$ mass distribution in the $J/ψ\to ϕηπ^+π^-$ decay and encourage further analysis to extract from there the $ϕπ^+ a_0^-$ and $ϕπ^- a_0^+$ decay modes.

hep-ph↗

arXiv2024

Molecular pentaquarks with hidden charm and double strangeness

We analyze theoretically the coupled-channel meson-baryon interaction with global flavor $\bar c c s s n$ and $\bar c c s s s$, where mesons are pseudoscalars or vectors and baryons have $J ^P=1/2^+$ or $3/2^+$. The aim is to explore whether the nonlinear dynamics inherent in the unitarization process within coupled channels can dynamically generate double- and triple-strange pentaquark-type states ($P_{css}$ and $P_{csss}$ respectively), for which there is no experimental evidence to date. We evaluate the s-wave scattering matrix by implementing unitarity in coupled channels, using potential kernels obtained from t-channel vector meson exchange. The required $PPV$ and $VVV$ vertices are obtained from Lagrangians derived through appropriate extensions of the local hidden gauge symmetry approach to the charm sector, while capitalizing on the symmetry of the spin and flavor wave function to evaluate the $BBV$ vertex. We find four different poles in the double strange sector, some of them degenerate in spin. For the triple-strange channel we find the meson-baryon interaction insufficient to generate a bound or resonance state through the unitary coupled-channel dynamics.

hep-ph↗

arXiv2024

Contrasting observables related to the $N^*(1535)$ from the molecular or a genuine structure

In this work we compare the predictions for the scattering length and effective range of the channels $K^0 Σ^+, K^+ Σ^0 , K^+ Λ$ and $ηp$, assuming the $N^*(1535)$ state as a molecular state of these channels, or an original genuine state, made for instance from three quarks. Looking at very different scenarios, what we conclude is that the predictions of these two pictures are drastically different, to the point that we advise the measurement of these magnitudes, accessible for instance by measuring correlation functions, in order to gain much valuable information concerning the nature of this state.

hep-ph↗

arXiv2023

Correlation function for the $T_{bb}$ state: Determination of the binding, scattering lengths, effective ranges and molecular probabilities

We perform a study of the $B^{*+}B^0,B^{*0}B^+$ correlation functions using an extension of the local hidden gauge approach which provides the interaction from the exchange of light vector mesons and gives rise to a bound state of these components in $I=0$ with a binding energy of about $21$~MeV. After that, we face the inverse problem of determining the low energy observables, scattering length and effective range for each channel, the possible existence of a bound state, and, if found, the couplings of such a state to each $B^{*+}B^0,B^{*0}B^+$ component as well as the molecular probabilities of each of the channels. We use the bootstrap method to determine these magnitudes and find that, with errors in the correlation function typical of present experiments, we can determine all these magnitudes with acceptable precision. In addition, the size of the source function of the experiment from where the correlation functions are measured can be also determined with a high precision.

hep-ph↗

arXiv2023

Correlation function for the $a_0(980)$

We have conducted a model independent analysis of the $K^+ \bar{K}^0$ pair correlation function obtained from ultra high energy $pp$ collisions, with the aim of extracting the information encoded in it related to the $K\bar{K}$ interaction and the coupled channel $π^+ η$. With the present large errors at small relative $K^+\bar{K}^0$ momenta, we find that the information obtained about the scattering matrix suffers from large uncertainties. Even then, we are able to show that the data imply the existence of the $a_0$ resonance, $a_0(980)$, showing as a strong cusp close to the $K\bar{K}$ threshold. We also mention that the measurement of the $π^+ η$ correlation function will be essential in order to constrain more the information on $K\bar{K}$ dynamics that can be obtained from correlation functions.

hep-ph↗