Song, J., Feijoo, A., & Oset, E. (2022). Role of meson interactions in the D-s(+) -> pi(+) pi(+) pi(-) eta decay. Phys. Rev. D, 106(7), 074027–20pp.
Abstract: We perform a theoretical study of the D-s(+) ->pi(+)pi(+)pi(-)eta decay. We look first at the basic D-s(+) decay at the quark level from external and internal emission. Then we hadronize a pair or two pairs of q (q) over bar states to have mesons at the end. Posteriorly the pairs of mesons are allowed to undergo final state interaction, by means of which the a(0)(980), f(0)(980), a(1)(1260), and b(1)(1235) resonances are dynamically generated. The G parity is used as a filter of the possible channels, and from those with negative G parity only the ones that can lead to pi(+)pi(+)pi(-)eta at the final state are kept. Using transition amplitudes from the chiral unitary approach that generates these resonances and a few free parameters, we obtain a fair reproduction of the six mass distributions reported in the BESIII experiment.
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Song, J., Dai, L. R., & Oset, E. (2022). How much is the compositeness of a bound state constrained by a and r(0)? The role of the interaction range. Eur. Phys. J. A, 58(7), 133–10pp.
Abstract: We present an approach that allows one to obtain information on the compositeness of molecular states from combined information of the scattering length of the hadronic components, the effective range, and the binding energy. We consider explicitly the range of the interaction in the formalism and show it to be extremely important to improve on the formula of Weinberg obtained in the limit of very small binding and zero range interaction. The method allows obtaining good information also in cases where the binding is not small. We explicitly apply it to the case of the deuteron and the D-s0* (2317) and D-s1* (2460) states and determine simultaneously the value of the compositeness within a certain range, as well as get qualitative information on the range of the interaction.
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Song, J., Dai, L. R., & Oset, E. (2023). Evolution of compact states to molecular ones with coupled channels: The case of the X(3872). Phys. Rev. D, 108(11), 114017–11pp.
Abstract: We study the molecular probability of the X(3872) in the D0 over bar D*0 and D+D*- channels in several scenarios. One of them assumes that the state is purely due to a genuine nonmolecular component. However, it gets unavoidably dressed by the meson components to the point that in the limit of zero binding of the D0 over bar D*0 component becomes purely molecular. Yet, the small but finite binding allows for a nonmolecular state when the bare mass of the genuine state approaches the D0 over bar D*0 threshold, but, in this case the system develops a small scattering length and a huge effective range for this channel in flagrant disagreement with present values of these magnitudes. Next we discuss the possibility to have hybrid states stemming from the combined effect of a genuine state and a reasonable direct interaction between the meson components, where we find cases in which the scattering length and effective range are still compatible with data, but even then the molecular probability is as big as 95%. Finally, we perform the calculations when the binding stems purely from the direct interaction between the meson-meson components. In summary we conclude, that while present data definitely rule out the possibility of a dominant nonmolecular component, the precise value of the molecular probability requires a more precise determination of the scattering length and effective range of the D0 over bar D*0 channel, as well as the measurement of these magnitudes for the D+D*- channel which have not been determined experimentally so far.
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Song, J., Liang, W. H., & Oset, E. (2025). Determination of the K+K0 scattering length and effective range from the D+→K0π+η reaction. Eur. Phys. J. C, 85(5), 513–9pp.
Abstract: We study the scattering parameters of the K+K0 system through the analysis of the D+-> K0 pi+eta reaction, aiming at determining the scattering length a and effective range r0 of the K+K0 interaction. These parameters are extracted by analyzing and fitting the mass distributions of the pairs in the final K0 pi+eta 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+K0 interaction at low energies.
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Song, J., Duan, M. Y., Roca, L., & Oset, E. (2024). Pentaquark molecular states with hidden bottom and double strangeness. Eur. Phys. J. C, 84(10), 1055–8pp.
Abstract: We investigate the meson-baryon interaction in coupled channels with the quantum numbers of the pentaquarks Pbss and Pbsss. The interaction is derived from an extension of the local hidden gauge approach to the heavy quark sector, which has demonstrated accurate results compared to experiments involving Ωb, Ξb states, and pentaquarks Pc and Pcs. In our study, we identify several molecular states with small decay widths within the chosen set of coupled channels. The spin-parity (JP) of these states is as follows: JP=12− for pseudoscalar-baryon (12+) coupled channels, JP=32− for pseudoscalar-baryon (32+) coupled channels, JP=12− and 32− for vector-baryon (12+) coupled channels, and JP=12−, 32−, 52− for vector-baryon (32+) coupled channels. We search for the poles of these states and evaluate their couplings to the different channels.
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Song, J., Liang, W. H., Xiao, C. W., Dias, J. M., & Oset, E. (2024). Testing the molecular nature of the Ω (2012) with the ψ (3770) → (Ω)over-bar(K)over-barΞ and ψ (3770) → (Ω)over-bar(K)over-barΞ* (1530) ((Ω)over-bar(K)over-barπΞ) reactions. Eur. Phys. J. C, 84(12), 1311–7pp.
Abstract: We report on the reactions psi(3770) -> (Omega) over bar+(K) over bar Xi and psi(3770) -> (Omega) over bar (+)(K) over bar Xi*(1530) (Xi* (1530) -> pi Xi), and calculate the mass distributions d Gamma/dM(inv)((K) over bar Xi) and d Gamma/dM(inv)(K Xi*), respectively. We obtain clear peaks corresponding to the Omega(2012). From the decay of psi(3770) -> (Omega) over bar (+)(K) over bar Xi*, we also get a second, broader, peak around 2035MeV, which comes from the Omega(2012) decay to (K) over bar Xi*. This second peak is closely tied to the molecular picture of the Omega(2012) with the (K) over bar Xi* (1530) and eta Omega components. Its observation would provide a boost to the molecular picture of the Omega (2012).
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Song, J., Yang, Z. Y., & Oset, E. (2025). Searching for signals of an exotic I=1,JP=2+ state of D*K* nature and the structure of the Pc(4312) in the Λb→Σc plus plus D-K- reaction. Phys. Lett. B, 861, 139294–7pp.
Abstract: This paper investigates the decay process Lambda-Sigma++-- with the objective of finding a predicted molecular state with isospin = 1, = 2+ of nature, plus finding support for the (4312) state as made out of Sigma. The mass distribution of the -- system shows distinct features as a consequence of the existence of this 2+ state, while the Sigma distribution exhibits a significant peak near the threshold, much bigger than phase space expectations, which is linked to our assumed Sigma nature of the (4312) state below the Sigma threshold. The reaction has been measured at LHCb Collaboration, but only the branching ratio is measured. The present study shows that much valuable information can be obtained about the predicted 2+ (2834) of nature and the (4312) states from the measurements of the mass distributions in this reaction, which will be accessible in the planned updates of LHCb.
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Song, J., Yang, Z. Y., & Oset, E. (2025). Searching for the 2+partner of the Tcs0(2870) in the B- -> D- D0 K0S reaction. Phys. Rev. D, 111(9), 094004–7pp.
Abstract: We study the B- -> D- D0 K0S reaction, recently analyzed by the LHCb Collaboration, where a clear signal for the exotic Tcs0(2870) state was reported. We call attention to a small peak in the D0K0S mass distribution that could correspond to a state of the same nature as the Tcs0(2870) (D*K<overline>* nature in the molecular picture), but with JP = 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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Song, J., Yang, Z. Y., & Oset, E. (2025). Role of a0(1710) in the Ds plus -> ρ plus φ;ρ plus ω decays. Phys. Rev. D, 111(9), 094047–7pp.
Abstract: We look into the D+s-* rho+phi and D+s-* rho+omega weak decays recently measured by the BESIII collaboration, which proceed very differently in a first step of the weak decay. While the first reaction proceeds directly via external emission, the second one does not go via external nor internal emission, what prompted the experimental team to claim that it proceeds via W-annihilation. We show in this work that the unexpectedly large rate of the D+s-* rho+omega has a different explanation since is it naturally obtained once final state interaction of the rho+phi; rho+omega and K*+K*0 channels is taken into consideration. The interaction of these channels produces the a0(1710) resonance, predicted long ago as a molecular state of these coupled channels, and only recently observed, and it is the presence of this resonance what makes the effect of the final state interaction very important in the weak decays and provides a natural explanation of the experimental decay rates at a quantitative level. We also take into account the D+s-* rho+omega decay in P-and D-waves empirically, and show that a good reproduction of the experimental results is obtained in this case.
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Solevi, P., Muñoz, E., Solaz, C., Trovato, M., Dendooven, P., Gillam, J. E., et al. (2016). Performance of MACACO Compton telescope for ion-beam therapy monitoring: first test with proton beams. Phys. Med. Biol., 61(14), 5149–5165.
Abstract: In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verification techniques are necessary to detect deviations from the planned treatment. Efforts are currently oriented towards the development of devices for real-time range monitoring. Among the different detector concepts proposed, Compton cameras are employed to detect prompt gammas and represent a valid candidate for real-time range verification. We present the first on-beam test of MACACO, a Compton telescope (multi-layer Compton camera) based on lanthanum bromide crystals and silicon photo-multipliers. The Compton telescope was first characterized through measurements and Monte Carlo simulations. The detector linearity was measured employing Na-22 and Am-Be sources, obtaining about 10% deviation from linearity at 3.44 MeV. A spectral image reconstruction algorithm was tested on synthetic data. Point-like sources emitting gamma rays with energy between 2 and 7 MeV were reconstructed with 3-5 mm resolution. The two-layer Compton telescope was employed to measure radiation emitted from a beam of 150 MeV protons impinging on a cylindrical PMMA target. Bragg-peak shifts were achieved via adjustment of the PMMA target location and the resulting measurements used during image reconstruction. Reconstructed Bragg peak profiles proved sufficient to observe peak-location differences within 10 mm demonstrating the potential of the MACACO Compton Telescope as a monitoring device for ion-beam therapy.
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