arXiv subjects

Albert Feijoo

Publications and source records attributed to Albert Feijoo.

18 recordsLinked to original sources

arXiv2026

Coulomb Effects in Momentum-Space Femtoscopy: A Case Study of the $\bar{K}\Omega$ System

We present a momentum-space framework for the consistent treatment of Coulomb interactions in femtoscopic correlation functions based on a modified Vincent--Phatak method that is more amenable to numerical implementation. The formalism provides a practical approach to incorporating Coulomb effects at the short distances relevant for femtoscopy within the Lippmann--Schwinger equation, while preserving a unified treatment of the strong interaction. As an application, we study the $S=-4$ pseudoscalar--baryon decuplet interaction in the $\bar{K}\Omega$ system and present predictions for the singly and doubly negatively charged channels, $\bar{K}^0\Omega^-$ and $K^-\Omega^-$. As an additional validation of the formalism, we have also applied it to the well-studied $pp$ system. We further assess the limitations of the asymptotic wave-function approximation and quantify corrections accounting for the short-distance structure of the interaction potential. We introduce a phenomenological parameter that effectively absorbs contributions from both the finite source size and the off-shell structure of the interaction, the latter being one of the main obstacles to extracting detailed information on hadron--hadron interactions from femtoscopic measurements in a model-independent way.

hep-ph↗

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.

hep-ph↗

arXiv2026

Signatures of the $\Omega(2012)^{-}$ state in $\Xi^*\bar K$ Correlation Functions

We investigate the $\Omega(2012)$ resonance in the strangeness $S=-3$ sector within a coupled-channel chiral unitary approach and present the first quantitative predictions for femtoscopic correlation functions directly sensitive to its dynamics. The $\Omega(2012)$ is dynamically generated as a quasi-bound $\Xi^{\ast}\bar K$-$\Omega\eta$ molecular state, with its coupling to the $\Xi\bar{K}$ channel driven by $d$-wave transitions. Model parameters are constrained by the measured mass, width, and the Belle determination of the branching fraction $\mathcal R^{\Xi\bar K\pi}_{\Xi\bar K}$, yielding $M_{\Omega(2012)}=(2012.53\pm0.73)$ MeV and $\Gamma_{\Omega(2012)}=(4.05\pm0.13)$ MeV. Within this framework, we compute the femtoscopic correlation functions of the $\Xi^{\ast0}K^-$, $\Xi^{\ast-}\bar K^0$, and $\Omega^-\eta$ systems. The $\Xi^{\ast}\bar K$ correlation functions exhibit pronounced near-threshold structures that arise from the proximity of the $\Omega(2012)$ pole, demonstrating an exceptional sensitivity to its position and coupled-channel composition. In particular, the $\Xi^{\ast0}K^-$ correlation function is identified as a clean and highly selective probe of the $\Omega(2012)$ resonance. These results establish femtoscopic correlation measurements as powerful tools for extracting resonance properties beyond conventional invariant-mass analyses and provide concrete theoretical benchmarks for upcoming experimental studies aimed at elucidating the molecular nature of the $\Omega(2012)$.

hep-ph↗

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.

hep-ph↗

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.

hep-ph↗

arXiv2025

Signatures of Odd-Parity $s$-wave $\Xi^*$ States in Femtoscopic Correlation Functions

We investigate the $\Xi^*$ resonances within the molecular picture, where these states are dynamically generated as poles in the unitarized scattering amplitudes arising from the coupled-channel interactions of $K^{*-} \Lambda$, $K^{*-} \Sigma^0$, $\rho^- \Xi^0$, $\overline{K}{}^{*0} \Sigma^-$, $\rho^0 \Xi^-$, $\omega \Xi^-$, and $\phi \Xi^-$. The interaction kernel is derived from the local hidden gauge formalism, while the unitarization procedure employs a hybrid method that combines cutoff and dimensional regularizations in the evaluation of the loop function. From a detailed spectroscopic analysis, we identify two $S = -2$ baryon states whose properties are compatible with some of the $\Xi^*$ resonances listed in the Review of Particle Physics. To explore their possible experimental signatures, we compute the femtoscopic correlation functions for all the vector-baryon pairs considered in the present study, using realistic estimates of production weights and varying source sizes $R = 1, 1.1, 1.2, 1.3, 1.5$ fm.

hep-ph↗

arXiv2025

Testing the nature of the $\Sigma^*(1430)$

We study the feasibility of having the $\Sigma^*(1430)$ 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 $\pi \Lambda$ channel, we allow the coupling to this state and relate the coupling to $\bar K N$ and $\pi \Sigma$ 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 $\Sigma^*(1430)$. 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.

hep-ph↗

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.

hep-ph↗

arXiv2024

On the possible existence of a $S=-3, \, I=1$ pentaquark

We analyze the possible existence of a strangeness $S=-3$, isospin $I=1$ pentaquark state $P_{sss}$ generated dynamically from the $\bar{K}\Xi$ interaction. We employ a unitarized scheme in coupled channels based on the chiral Lagrangian expanded up to next-to-leading order (NLO), and show that the inclusion of the NLO terms is crucial to provide the necessary attraction that favors the existence of such triply strange pentaquark. The $\bar{K}\Xi$ femtoscopic correlation functions are calculated as example of a possible experimental measurement in which a direct signal of the $P_{sss}$ state could be observed.

hep-ph↗

arXiv2024

Femtoscopy study of $\pi^-\Lambda$ and $K^-p$ interactions

We have calculated the femtoscopic correlation functions of meson-baryon pairs in the strangeness $S=-1$ sector, employing a unitarized chiral interaction model up to next-to-leading order. We will show preliminary results for the $\pi^-\Lambda$ correlation function, which is presently under analysis by the ALICE@LHC collaboration. We will also demonstrate that, within $2\sigma$, the employed interaction is perfectly capable of reproducing the $K^-p$ correlation function data measured by the same collaboration, without the need of changing the coupled-channel interactions, as has been suggested recently.

hep-ph↗

arXiv2023

A new look at the $P_{cs}$ states from a molecular perspective

We have a look at the $P_{cs}$ states generated from the interaction of $\bar D^{(*)} Ξ^{(\prime*)}_c$ coupled channels. We consider the blocks of pseudoscalar-baryon $({\frac12}^+, {\frac32}^+)$ and vector-baryon $({\frac12}^+, {\frac32}^+)$, and find $10$ resonant states coupling mostly to $\bar D Ξ_c, \bar D^* Ξ_c,\bar D Ξ'_c, \bar D^* Ξ'_c,\bar D Ξ^*_c$ and $\bar D^* Ξ^*_c$. A novel aspect of the work is the realization that the $\bar D Ξ_c,\bar D_sΛ_c$ or $\bar D^* Ξ_c,\bar D^*_sΛ_c$ channels, with a strong transition potential, collaborate to produce a larger attraction than the corresponding states $\bar D Σ_c,\bar DΛ_c$ or $\bar D^* Σ_c,\bar D^*Λ_c$ appearing in the generation of the strangenessless $P_{c}$ states, since in the latter case the transition potential between those channels is zero. The extra attraction obtained in the $\bar D Ξ_c,\bar D^* Ξ_c$ pairs preclude the association of these channels to the $P_{cs}(4338)$ and $P_{cs}(4459)$ states respectively. Then we find a natural association of the $P_{cs}(4338)$ state coupling mostly to $\bar D^* Ξ_c$ while the $P_{cs}(4459)$ is associated to the state found that couples mostly to $\bar D Ξ'_c$. Four more states appear, like in other molecular pictures, and some of the states are degenerate in spin. Counting different spin states we find $10$ states, which we hope can be observed in the near future.

hep-ph↗

arXiv2022

Molecular $Ω_{cc}$ , $Ω_{bb}$ and $Ω_{bc}$ states

We study the interaction of meson-baryon coupled channels carrying quantum numbers of $Ω_{cc}$ , $Ω_{bb}$ and $Ω_{bc}$ presently under investigation by the LHCb collaboration. The interaction is obtained from an extension of the local hidden gauge approach to the heavy quark sector that has proved to provide accurate results compared to experiment in the case of $Ω_{c}$ , $Ξ_{c}$ states and pentaquarks, $P_c$ and $P_{cs}$. We obtain many bound states, with small decay widths within the space of the chosen coupled channels. The spin-parity of the states are $J^P={\frac{1}{2}}^-$ for coupled channels of pseudoscalar-baryon (${\frac{1}{2}}^+$), $J^P={\frac{3}{2}}^-$ for the case of pseudoscalar-baryon (${\frac{3}{2}}^+$), $J^P={\frac{1}{2}}^-,{\frac{3}{2}}^-$ for the case of vector-baryon (${\frac{1}{2}}^+$) and $J^P={\frac{1}{2}}^-,{\frac{3}{2}}^-,{\frac{5}{2}}^-$ for the vector-baryon (${\frac{3}{2}}^+$) channels. We look for poles of the states and evaluate the couplings to the different channels. The couplings obtained for the open channels can serve as a guide to see in which reaction the obtained states are more likely to be observed.

hep-ph↗

arXiv2021

The ${\bar K}N$ interaction in higher partial waves

We present a chiral ${\bar K}N$ interaction model that has been developed and optimized in order to account for the experimental data of inelastic ${\bar K}N$ reaction channels that open at higher energies. In particular, we study the effect of the higher partial waves which originate directly from the chiral Lagrangian, as they could supersede the role of high-spin resonances employed in earlier phenomenological models to describe meson-baryon cross sections in the 2~GeV region. We present a detailed derivation of the partial wave amplitudes that emerge from the chiral SU(3) meson-baryon Lagrangian up to the d-waves and next-to-leading order in the chiral expansion. We implement a nonperturbative unitarization in coupled channels and optimize the model parameters to a large pool of experimental data in the relevant energy range where these new contributions are expected to be important. The obtained results are encouraging. They indicate the ability of the chiral higher partial waves to extend the description of the scattering data to higher energies and to account for structures in the reaction cross sections that cannot be accommodated by theoretical models limited to the s-waves.

hep-ph↗

arXiv2021

$Λ(1405)$ mediated triangle singularity in the $K^-d\to pΣ^-$ reaction

We study for the first time the $pΣ^-\to K^-d$ and $K^-d\to pΣ^-$ reactions close to threshold and show that they are driven by a triangle mechanism, with the $Λ(1405)$, a proton and a neutron as intermediate states, which develops a triangle singularity close to the $\bar{K}d$ threshold. We find that a mechanism involving virtual pion exchange and the $K^-p\toπ^+Σ^-$ amplitude dominates over another one involving kaon exchange and the $K^-p\to K^-p$ amplitude. Moreover, of the two $Λ(1405)$ states, the one with higher mass around $1420$ MeV, gives the largest contribution to the process. We show that the cross section, well within measurable range, is very sensitive to different models that, while reproducing $\bar{K}N$ observables above threshold, provide different extrapolations of the $\bar{K}N$ amplitudes below threshold. The observables of this reaction will provide new constraints on the theoretical models, leading to more reliable extrapolations of the $\bar{K}N$ amplitudes below threshold and to more accurate predictions of the $Λ(1405)$ state of lower mass.

nucl-th↗

arXiv2019

$S=-1$ meson-baryon interaction and the role of isospin filtering processes

A study of the meson-baryon interaction in the $S=-1$ sector is performed, employing a chiral SU(3) lagrangian up to next-to-leading order (NLO) and implementing unitarization in coupled channels. The model is constrained by a large set of experimental data, paying a especial attention to processes that are sensitive to the NLO contributions, such as the $K^- p\to K^+Ξ^-, K^0Ξ^0$ reactions. The consideration of additional cross sections in single isospin channels, $K^-p\to ηΛ, ηΣ$, has been found to provide more homogeneous and reliable values of the low-energy constants, the stability of which has also been tested by the inclusion of explicit resonant terms. Predictions for new isospin filtering processes, like the $I=1$ $K^0_L p \to K^+ Ξ^0$ reaction that could be measured at the proposed secondary $K^0_L$ beam at Jlab, or the weak decay of the $Λ_b$ into a $J/Ψ$ and different meson-baryon pairs in $I=0$, available at LHCb, are presented. The measurement of such reactions would put valuable constraints on the chiral models describing the $S=-1$ meson-baryon interaction.

hep-ph↗

arXiv2018

The molecular nature of some $Ω_c^0$ states

A vector meson exchange model based on effective Lagrangians is used to build the meson--baryon interaction in the charm $+1$, strangeness $-2$ and isospin $0$ sector. The s-wave scattering amplitudes resulting from the unitarization in coupled-channels show two resonances with masses and widths that are in very good agreement with those of the experimental $Ω_c(3050)^0$ and $Ω_c(3090)^0$ states observed by the LHCb collaboration. The interpretation of these resonances as pseudoscalar meson--baryon molecules would mean the assignment $J^P=1/2^-$ to their spin--parity.

hep-ph↗

arXiv2018

Exotic $Ω_c^0$ baryons from meson-baryon scattering

A meson-baryon interaction in the charm $+1$, strangeness $-2$ and isospin $0$ sector is built from a t-channel vector meson exchange model employing effective Lagrangians. The implementation of coupled-channel unitarization in the s-wave scattering amplitudes gives rise to two structures that have similar masses and widths to those of the $Ω_c(3050)^0$ and $Ω_c(3090)^0$ states recently observed by the LHCb collaboration. A meson-baryon molecular interpretation of these resonances would assign their spin-parity to be $J^P=1/2^-$.

hep-ph↗

arXiv2017

A meson-baryon molecular interpretation for some $Ω_c$ excited baryons

We explore the possibility that some of the five narrow $Ω_c$ resonances recently observed at LHCb could correspond to pentaquark states, structured as meson-baryon bound states or molecules. The interaction of the low-lying pseudoscalar mesons with the ground-state baryons in the charm $+1$, strangeness $-2$ and isospin 0 sector is built from t-channel vector meson exchange, using effective Lagrangians. The resulting s-wave coupled-channel unitarized amplitudes show the presence of two structures with similar masses and widths to those of the observed $Ω_c(3050)^0$ and $Ω_c(3090)^0$. The identification of these resonances with the meson-baryon bound states found in this work would also imply assigning the values $1/2^-$ for their spin-parity. An experimental determination of the spin-parity of the $Ω_c(3090)^0$ would help in disentangling its structure, as the quark-based models predict its spin-parity to be either $3/2^-$ or $5/2^-$.

hep-ph↗