Bayar, M., Feijoo, A., & Oset, E. (2023). X(3960) seen in Ds plus Ds- as the X(3930) state seen in D plus D. Phys. Rev. D, 107(3), 034007–5pp.
Abstract: We perform a calculation of the interaction of the D over bar D, Ds over bar Ds coupled channels and find two bound states, one coupling to DD over bar and another one at higher energies coupling mostly to D+s D-s . We identify this latter state with the X0(3930) seen in the D+D- mass distribution in the B+ -D+D-K+ decay, and also show that it produces an enhancement of the D+s D-s mass distribution close to threshold which is compatible with the recent LHCb observation in the B+ -D+s D-s K+ decay which has been identified as a new state, X0(3960).
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Feijoo, A., Dai, L. R., Abreu, L. M., & Oset, E. (2024). Correlation function for the Tbb state: Determination of the binding, scattering lengths, effective ranges, and molecular probabilities. Phys. Rev. D, 109(1), 016014–8pp.
Abstract: We perform a study of the (B*+B0), (BB+)-B-*0 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*+B0), (BB+)-B-*0 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.
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Mantovani Sarti, V., Feijoo, A., Vidana, I., Ramos, A., Giacosa, F., Hyodo, T., et al. (2024). Constraining the low-energy S =-2 meson-baryon interaction with two-particle correlations. Phys. Rev. D, 110(1), L011505–8pp.
Abstract: In this paper we present a novel method to extract information on hadron-hadron interactions using for the first time femtoscopic data to constrain the low-energy constants of a QCD effective Lagrangian. This method offers a new way to investigate the nonperturbative regime of QCD in sectors where scattering experiments are not feasible, such as the multistrange and charm ones. As an example of its application, we use the very precise K-Lambda correlation function data, recently measured in pp collisions at LHC, to constrain the strangeness S = -2 meson-baryon interaction. The model obtained delivers new insights on the molecular nature of the Xi(1620) and Xi(1690) states.
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Albaladejo, M., Feijoo, A., Nieves, J., Oset, E., & Vidaña, I. (2024). Femtoscopy correlation functions and mass distributions from production experiments. Phys. Rev. D, 110(11), 114052–21pp.
Abstract: 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 (DD)-D-0*(+) and D+D*(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 behavior of the LL CF in the punctual source-size limit.
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Feijoo, A., Mantovani Sarti, V., Nieves, J., Ramos, A., & Vidaña, I. (2025). Bridging correlation and spectroscopy measurements to access the hadron interaction behind molecular states: The case of the Ξ(1620) and Ξ(1690) in the K – Λ system. Phys. Rev. D, 111(1), 014022–15pp.
Abstract: We study the compatibility between the K-A correlation function, recently measured by the ALICE collaboration, and the LHCb K-A invariant mass distribution obtained in the -b -> J/psi AK- decay. The K-A invariant mass distribution associated with the – b decay has been calculated within the framework of unitary effective field theories using two models, one of them constrained by the K-A correlation function. We consider two degenerate pentaquark PAs states in the J/psi A scattering amplitude which allows us to investigate their impact on both the K-A and J/psi A mass distributions assuming different spin-parity quantum numbers and multiplicity. Without any fitting procedure, the K-A model is able to better reproduce the experimental K-A mass spectrum in the energy region above 1680 MeV as compared to previous unitarized scattering amplitudes constrained to a large amount of experimental data in the neutral S = -1 meson-baryon sector. We observe a tension between our model and the LHCb K-A distribution in the region close to threshold, largely dominated by the presence of the still poorly known (1620) state. We discuss in detail the different production mechanisms probed via femtoscopy and spectroscopy that could provide valid explanations for such disagreement, indicating the necessity to employ future correlation data in other S = -2 channels such as pi and K<overline>Sigma.
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