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Xie, J. J., Liang, W. H., & Oset, E. (2019). eta-He-4 interaction from the dd->eta He-4 reaction near threshold. Eur. Phys. J. A, 55(1), 6–8pp.
Abstract: .We analyze the data on the total cross sections for the dd4 He reaction close to threshold and look for possible 4 He bound states. We develop a framework in which the 4 He optical potential is the key ingredient, rather than parameterizing the scattering matrix, as is usually done. The strength of this potential, together with some production parameters, are fitted to the available experimental data. The relationship of the scattering matrix to the optical potential is established using the Bethe-Salpeter equation and the 4 He loop function incorporates the range of the interaction given by the experimental He-4 density. However, when we look for poles of the scattering matrix, we get poles in the bound region, poles in the positive energy region or no poles at all. If we further restrict the results with constraints from a theoretical model with all its uncertainties the bound states are not allowed. However, we find a bump structure in |T|2 of the 4 He 4 He scattering amplitude below threshold for the remaining solutions.
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Wang, E., Liang, W. H., & Oset, E. (2021). Analysis of the e(+)e(-) -> J/psi D(D)over-bar reaction close to the threshold concerning claims of a chi(c0)(2P) state. Eur. Phys. J. A, 57(1), 38–9pp.
Abstract: We analyze the D (D) over bar mass distribution from a recent Belle experiment on the e(+)e(-) -> J/.D (D) over bar reaction, and show that the mass distribution divided by phase sp(c)e does not have a clear peak above the D (D) over bar threshold that justifies the experimental claim of chi(c0)(2P) state from those data. Then we use a unitary formalismwith coupled channels D+ D-, D-0 (D) over bar (0), D-s(D) over bar (s), and eta eta, with some of the interactions taken from a theoretical model, and use the data to fix other parameters. We then show that, given the poor quality of the data, we can get different fits leading to very different D (D) over bar amplitudes, some of them supporting a D (D) over bar bound state and others not. The main conclusion is that the claim for the chi(c0)(2P) state, already included in the PDG, is premature, but refined data can provide very valuable information on the D (D) over bar scattering amplitude. As side effects, we warn about the use of a Breit-Wigner amplitude parameterization close to threshold, and show that the D-s(D) over bar (s) channel plays an important role in this reaction.
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Liang, W. H., Xie, J. J., & Oset, E. (2015). (B)over-bar(0), B- and (B)over-bar(S)(0) decays into J/psi and K (K)over-bar or pi eta. Eur. Phys. J. C, 75(12), 609–8pp.
Abstract: We study the (B) over bar (0)(S) -> J/psi K+ K-, (B) over bar (0) -> J/psi K+ K, B- -> J/psi K+ K-, (B) over bar (0) -> J/psi pi(0)eta(-), decays and compare their mass distributions with those obtained for the (B) over bar (0)(S) -> J/psi pi(+) pi(-) and (B) over bar (0)(S) -> J/psi pi(+)pi(-). The approach followed consist in a factorization of the weak part and the hadronization part into a factor which is common to all the processes. Then what makes the reactions different are some trivial CabibboKobayashi- Maskawa matrix elements and the weight by which the different pairs of mesons appear in a primary step plus their final state interaction. These elements are part of the theory and thus, up to a global normalization factor, all the invariant mass distributions are predicted with no free parameters. Comparison is made with the limited experimental information available. Further comparison of these results with coming LHCb measurements will be very valuable to make progress in our understanding of the meson- meson interaction and the nature of the low lying scalar meson resonances, f(0)(500), f(0)( 980) and a(0)(980).
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Liang, W. H., Xie, J. J., & Oset, E. (2016). f(0)(500), f(0)(980), and a(0)(980) production in the chi(c1) -> eta pi(+)pi(-) reaction. Eur. Phys. J. C, 76(12), 700–7pp.
Abstract: We study the chi(c1) -> eta pi(+)pi(-) decay, paying attention to the production of f(0)(500), f(0)(980), and a(0)(980) from the final state interaction of pairs of mesons that can lead to these three mesons in the final state, which is implemented using the chiral unitary approach. Very clean and strong signals are obtained for the a(0)(980) excitation in the eta pi invariant mass distribution and for the f(0)(500) in the pi(+)pi(-) mass distribution. A smaller, but also clear signal for the f(0)(980) excitation is obtained. The results are contrasted with experimental data and the agreement found is good, providing yet one more test in support of the picture where these resonances are dynamically generated from the meson-meson interaction.
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Pavao, R. P., Liang, W. H., Nieves, J., & Oset, E. (2017). Predictions for Xi(-)(b) -> pi-(D-S(-)) Xi(0)(C) (2790) (Xi(0)(C)(2815) and Xi(-)(b) -> (v)over-bar (l)l Xi(0)(C)(2790) (Xi(0)(C)(2815). Eur. Phys. J. C, 77(4), 265–12pp.
Abstract: We have performed calculations for the non-leptonic Xi(-)(b) -> pi-(D-S(-)) Xi(0)(C) (2790)(J = 1/2) Xi(-)(b) -> pi(-) Xi(0)(C)(2815) (J = 3/2) and decays and the same reactions replacing the pi- by a D-s(-). At the same time we have also evaluated the semileptonic rates for and Xi(-)(b) -> pi-(D-S(-)) Xi(0)(C) (2790). We look at the reactions from the perspective that the Xi(0(2790))(c) and Xi(0)(c)(2815()) resonances are dynamically generated from the pseudoscalar-baryon and vector-baryon interactions. We evaluate ratios of the rates of these reactions and make predictions that can be tested in future experiments. We also find that the results are rather sensitive to the coupling of the Xi(c)* resonances to the D*Sigma and D*A components.
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Liang, W. H., Bayar, M., & Oset, E. (2017). Lambda(b) -> pi(-)(D-S(-)) Lambda(C)(2595), pi(-)(D-S(-)) Lambda(C)(2625) decays and DN, D*N molecular components. Eur. Phys. J. C, 77(1), 39–9pp.
Abstract: From the perspective that Lambda(C)(2595) and Lambda(C)(2625) are dynamically generated resonances from the DN, D*N interaction and coupled channels, we have evaluated the rates for Lambda(b) -> pi(-)Lambda(C)(2595) and Lambda(b) -> pi(-)Lambda(C)(2625) up to a global unknown factor that allows us to calculate the ratio of rates and compare with experiment, where good agreement is found. Similarly, we can also make predictions for the ratio of rates of the, yet unknown, decays of Lambda(b) -> D-s(-)Lambda(C)(2595) and Lambda(b) -> D-s(-)Lambda(c)(2625) and make estimates for their individual branching fractions.
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Liang, W. H., & Oset, E. (2018). Pseudoscalar or vector meson production in non-leptonic decays of heavy hadrons. Eur. Phys. J. C, 78(6), 528–26pp.
Abstract: We have addressed the study of non-leptonic weak decays of heavy hadrons (Lambda b, Lambda c, B and D), with external and internal emission to give two final hadrons, taking into account the spin-angular momentum structure of the mesons and baryons produced. A detailed angular momentum formulation is developed which leads to easy final formulas. By means of them we have made predictions for a large amount of reactions, up to a global factor, common tomany of them, that we take from some particular data. Comparing the theoretical predictions with the experimental data, the agreement found is quite good in general and the discrepancies should give valuable information on intrinsic form factors, independent of the spin structure studied here. The formulas obtained are also useful in order to evaluate meson-meson or meson-baryon loops, for instance of B decays, in which one has PP, PV, VP or VV intermediate states, with P for pseudoscalar mesons and V for vector meson and lay the grounds for studies of decays into three final particles.
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Liang, W. H., Chen, H. X., Oset, E., & Wang, E. (2019). Triangle singularity in the J/psi -> K+K- f(0)(980)(a(0)(980)) decays. Eur. Phys. J. C, 79(5), 411–11pp.
Abstract: We study the J/psi -> K+K- f(0)(980)(a(0)(980)) reaction and find that the mechanism to produce this decay develops a triangle singularity around M-inv(K- f(0)/K- a(0)) approximate to 1515 MeV. The differential width d Gamma/dM(inv)(K- f(0)/K- a(0)) shows a rapid growth around the invariant mass being 1515 MeV as a consequence of the triangle singularity of this mechanism, which is directly tied to the nature of the f(0)(980) and a(0)(980) as dynamically generated resonances from the interaction of pseudoscalar mesons. The branching ratios obtained for the J/psi -> K+K- f(0)(980)(a(0)(980)) decays are of the order of 10(-5), accessible in present facilities, and we argue that their observation should provide relevant information concerning the nature of the low-lying scalar mesons.
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Yu, Q. X., Dias, J. M., Liang, W. H., & Oset, E. (2019). Molecular Xi(bc) states from meson-baryon interaction. Eur. Phys. J. C, 79(12), 1025–13pp.
Abstract: We have studied the meson-baryon interaction in coupled channels with the same quantum numbers of Xi bc. The interaction is attractive in some channels and of sufficient intensity to lead to bound states or resonances. We use a model describing the meson-baryon interaction based on an extrapolation of the local hidden gauge approach to the heavy sector, which has been successfully used in predicting omega c and hidden charm states. We obtain many states, some of them narrow or with zero width, as a consequence of the interaction, which qualify as molecular states in those channels. The success in related sectors of the picture used should encourage the experimental search for such states.
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Liang, W. H., & Oset, E. (2020). Testing the origin of the f1(1420) with the Kbar p -> Lambda(Sigma) K Kbar pi reaction. Eur. Phys. J. C, 80(5), 407–8pp.
Abstract: We study the K¯p→YKK¯π reactions with K¯=K¯0,K− and Y=Σ0,Σ+,Λ, in the region of KK¯π invariant masses of 1200−1550 MeV. The strong coupling of the f1(1285) resonance to K∗K¯ makes the mechanism based on K∗ exchange very efficient to produce this resonance observed in the KK¯π invariant mass distribution. In addition, in all the reactions one observes an associated peak at 1420 MeV which comes from the K∗K¯ decay mode of the f1(1285) when the K∗ is placed off shell at higher invariant masses. We claim this to be the reason for the peak of the K∗K¯ distribution seen in the experiments which has been associated to the “f1(1420)” resonance.
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