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Brandao, P. C. S., Song, J., Abreu, L. M., & Oset, E. (2023). B+ decay to K+ ηη with (ηη) from the D bar-D(3720) bound state. Phys. Rev. D, 108(5), 054004–6pp.
Abstract: We search for a B decay mode where one can find a peak for a DD bound state predicted in effective theories and in lattice QCD calculations, which has also been claimed from some reactions that show an accumulated strength in D D over bar production at threshold. We find a good candidate in the B+-> K+eta eta reaction, by looking at the eta eta mass distribution. The reaction proceeds via a first step in which one has the B+-> D*+ D-0 reaction followed by D*(+) (s) decay to (DK+)-K-0 and a posterior fusion of D-0 over bar D-0 to eta eta, implemented through a triangle diagram that allows the D-0 over bar D-0 to be virtual and to produce the bound state. The choice of eta eta to see the peak is based on results of calculations that find the eta eta among the light pseudoscalar channels with stronger coupling to the D D over bar bound state. We find a neat peak around the predicted mass of that state in the eta eta mass distribution, with an integrated branching ratio for B+-> K+ (D D, bound); (D D, bound) -> eta eta of the order of 1.5 x 10(-4), a large number for hadronic B decays, which should motivate its experimental search.
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Li, H. P., Zhang, G. J., Liang, W. H., & Oset, E. (2023). Theoretical interpretation of the Ξ(1620) and Ξ(1690) resonances seen in Ξc+ → Ξ-π+π+ decay. Eur. Phys. J. C, 83(10), 954–7pp.
Abstract: We study the Belle reaction Xi(+)(c) -> Xi(-)pi(+)pi(+) looking at the mass distribution of pi(+)Xi, where clear signals for the Xi(1620) and Xi(1690) resonances are seen. These two resonances are generated dynamically from the interaction in coupled channels of pi Xi, (K) over bar Lambda, (K) over bar Xi and eta Xi within the chiral unitary approach. Yet, the weak decay process at the quark level, together with the hadronization to produce pairs of mesons, does not produce the pi pi Xi final state. In order to produce this state one must make transitions from the (K) over bar Lambda, (K) over bar Xi and eta Xi components to pi Xi, and this interaction is what produces the resonances. So, the reaction offers a good test for the molecular picture of these resonances. Adding the contribution of the Xi*(1530) and some background we are able to get a good reproduction of the mass distribution showing the signatures of the two resonances as found in the experiment.
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Vidaña, I., Feijoo, A., Albaladejo, M., Nieves, J., & Oset, E. (2023). Femtoscopic correlation function for the Tcc(3875)+ state. Phys. Lett. B, 846, 138201–9pp.
Abstract: We have conducted a study of the femtoscopic correlation functions for the D0D*+ and D+D*0 channels that build the Tcc state. We develop a formalism that allows us to factorize the scattering amplitudes outside the integrals in the formulas, and the integrals involve the range of the strong interaction explicitly. For a source of size of 1 fm, we find values for the correlation functions of the D0D*+ and D+D*0 channels at the origin around 30 and 2.5, respectively, and we see these observables converging to unity already for relative momenta of the order of 200 MeV. We conduct tests to see the relevance of the different contributions to the correlation function and find that it mostly provides information on the scattering length, but should the correlation functions be measured with the precision of the latest experiments, the effective range of the D0D*+ could also be obtained.
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Dai, L. R., Abreu, L. M., Feijoo, A., & Oset, E. (2023). The isospin and compositeness of the Tcc(3875) state. Eur. Phys. J. C, 83(10), 983–11pp.
Abstract: We perform a fit to the LHCb data on the T-cc(3875) state in order to determine its nature. We use a general framework that allows to have the (DD & lowast;+)-D-0, (D+D & lowast;0) components forming a molecular state, as well as a possible nonmolecular state or contributions from missing coupled channels. From the fits to the data we conclude that the state observed is clearly of molecular nature from the (DD & lowast;+)-D-0, (D+D & lowast;0) components and the possible contribution of a nonmolecular state or missing channels is smaller than 3%, compatible with zero. We also determine that the state has isospin I=0 with a minor isospin breaking from the different masses of the channels involved, and the probabilities of the (DD & lowast;+)-D-0, (D+D & lowast;0) channels are of the order of 69% and 29% with uncertainties of 1%. The differences between these probabilities should not be interpreted as a measure of the isospin violation. Due to the short range of the strong interaction where the isospin is manifested, the isospin nature is provided by the couplings of the state found to the (DD & lowast;+)-D-0, (D+D & lowast;0) components, and our results for these couplings indicate that we have an I=0 state with a very small isospin breaking. We also find that the potential obtained provides a repulsive interaction in I=1, preventing the formation of an I=1 state, in agreement with what is observed in the experiment.
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Abreu, L. M., Ikeno, N., & Oset, E. (2023). Role of f0(980) and a0(980) in the B- → π-K+K- and B- → π-K0Kbar0 reactions. Phys. Rev. D, 108(1), 016007–9pp.
Abstract: In this work we study the role of the f(0)(980) and a(0)(980) resonances in the low K+K- and K-0(K) over bar (0) invariant-mass region of the B- -> pi-K+K- and B- -> pi K--(0)(K) over bar (0) reactions. The amplitudes are calculated by using the chiral unitary SU(3) formalism, in which these two resonances are dynamically generated from the unitary pseudoscalar-pseudoscalar coupled-channel approach. The amplitudes are then used as input in the evaluation of the mass distributions with respect to the K+K- and K-0(K) over bar (0) invariant masses, where the contributions coming from the I = 0 and I = 1 components are explicitly assessed. Furthermore, the contribution of the K*(892)K-0(-) production and its influence on the pi K--(+) and K+K- systems are also evaluated, showing that there is no significant strength for small K+K- invariant mass. Finally, the final distributions of M-inv(2) ((KK -/+)-K-+/-) for the B--/+ -> pi(KK -/+)-K--/+-K-+/- reactions are estimated and compared with the LHCb data. Our results indicate that the I = 0 component tied to the f(0)(980) excitation generates the dominant contribution in the range of low K+K- invariant mass.
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Ikeno, N., Toledo, G., & Oset, E. (2023). Model independent analysis of femtoscopic correlation functions: An application to the D∗s0(2317). Phys. Lett. B, 847, 138281–6pp.
Abstract: We face the inverse problem of obtaining the interaction between coupled channels from the correlation functions of these channels. We apply the method to the interaction of the (DK+)-K-0, (D+K0), and D-s(+)eta channels, from where the D-s0(& lowast;)(2317) state emerges. We use synthetic data extracted from an interaction model based on the local hidden gauge approach and find that the inverse problem can determine the existence of a bound state of the system with a precision of about 20 MeV. At the same time, we can determine the isospin nature of the bound state and its compositeness in terms of the channels. Furthermore, we evaluate the scattering length and effective range of all three channels, as well as the couplings of the bound state found to all the components. Lastly, the size parameter of the source function, R, which in principle should be a magnitude provided by the experimental teams, can be obtained from a fit to the data with relatively high accuracy. These findings show the value of the correlation function to learn about the meson-meson interaction for systems which are difficult to access in other present facilities.
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Lin, J. X., Li, J. T., Liang, W. H., Chen, H. X., & Oset, E. (2024). J/ψ decays into ω(φ) f1(1285) and ω(φ) “f1(1420)”. Eur. Phys. J. C, 84(1), 52–8pp.
Abstract: We perform a theoretical study of the J/psi -> omega (Phi)K* K + c.c. -> omega(Phi)K-0 pi+ K- reactions with the assumption that the f1(1285) is dynamically generated from a single channel K*K + c.c interaction in the chiral unitary approach. Two peaks in the K-0 pi+ K- invariant mass distribution are observed, one clear peak locates at the f(1)(1285) nominal mass, the other peak locates at around 1420MeV with about 70MeV width. We conclude that the former peak is associated with the f(1)(1285) and the latter peak is not a genuine resonance but a manifestation of the kinematic effect in the higher energy region caused by the K* K + c.c. decay mode of the f(1)(1285).
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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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Molina, R., Xiao, C. W., Liang, W. H., & Oset, E. (2024). Correlation functions for the N*(1535) and the inverse problem. Phys. Rev. D, 109(5), 054002–10pp.
Abstract: The N*(1535) can be dynamically generated in the chiral unitary approach with the coupled channels, K0E+; K+E0; K+A, and eta p. In this work, we evaluate the correlation functions for every channel and face the inverse problem. Assuming the correlation functions to correspond to real measurements, we conduct a fit to the data within a general framework in order to extract the information contained in these correlation functions. The bootstrap method is used to determine the uncertainties of the different observables, and we find that, assuming errors of the same order than in present measurements of correlation functions, one can determine the scattering length and effective range of all channels with a very good accuracy. Most remarkable is the fact that the method predicts the existence of a bound state of isospin 12 nature around the mass of the N*(1535) with an accuracy of 6 MeV. These results should encourage the actual measurement of these correlation functions (only the K+A one is measured so far), which can shed valuable light on the relationship of the N*(1535) state to these coupled channels, a subject of continuous debate.
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Molina, R., Liu, Z. W., Geng, L. S., & Oset, E. (2024). Correlation function for the a0(980). Eur. Phys. J. C, 84(3), 328–8pp.
Abstract: We have conducted a model independent analysis of the (K+K0) pair correlation function obtained from ultra high energy pp collisions, with the aim of extracting the information encoded in it related to the KK interaction and the coupled channel pi(+)eta. With the present large errors at small relative (K+K0) 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 KK threshold. We also mention that the measurement of the pi(+)eta correlation function will be essential in order to constrain more the information on KK dynamics that can be obtained from correlation functions.
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