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Debastiani, V. R., Liang, W. H., Xie, J. J., & Oset, E. (2017). Predictions for eta(c) -> eta pi(+)pi(-) producing f(0)(500), f(0)(980) and a(0)(980). Phys. Lett. B, 766, 59–64.
Abstract: We perform calculations for the eta(c) -> eta pi(+)pi(-) decay using elements of SU(3) symmetry to see the weight of different trios of pseudoscalars produced in this decay, prior to the final state interaction of the mesons. After that, the interaction of pairs of mesons, leading finally to eta pi(+)pi(-), is done using the chiral unitary approach. We evaluate the pi(+)pi(-) and pi eta mass distributions and find large and clear signals for f(0)(500), f(0)(980) and a(0)(980) excitation. The reaction is similar to the chi(c1) -> eta pi(+)pi(-), which has been recently measured at BESIII and its implementation and comparison with these predictions will be very valuable to shed light on the nature of the low mass scalar mesons.
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Liang, W. H., Sakai, S., Xie, J. J., & Oset, E. (2018). Triangle singularity enhancing isospin violation in (B)over-bar(s)(0)-> J/psi pi(0)f(0)(980). Chin. Phys. C, 42(4), 044101–9pp.
Abstract: We perform calculations for the (B) over bar (0)(s)-> J/psi pi(0)f(0)(980) and (B) over bar (0)(s)-> J/psi pi(0)a(0)(980) reactions, showing that the first is isospin-suppressed while the second is isospin-allowed. The reaction proceeds via a triangle mechanism, with (B) over bar (0)(s)-> J/psi K*(K) over bar +c.c., followed by the decay K*-> K pi and a further fusion of K (K) over bar into the f(0)(980) or a(0)(980). We show that the mechanism develops a singularity around the pi(0)f(0)(980) or pi(0)a(0)(980) invariant mass of 1420 MeV, where the pi(0)f(0) and pi(0)a(0) decay modes are magnified and also the ratio of pi(0)f(0) to pi(0)a(0) production. Using experimental information for the (B) over bar (0)(s)-> J/psi K*(K) over bar +c.c. decay, we are able to obtain absolute values for the reactions studied which fall into the experimentally accessible range. The reactions proposed and the observables evaluated, when contrasted with actual experiments, should be very valuable to obtain information on the nature of the low lying scalar mesons.
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Feijoo, A., Liang, W. H., & Oset, E. (2021). (DD0)-D-0 pi(+) mass distribution in the production of the T-cc exotic state. Phys. Rev. D, 104(11), 114015–7pp.
Abstract: We perform a unitary coupled channel study of the interaction of the D*D-+(0), D*D-0(+) channels and find a state barely bound, very close to isospin I = 0. We take the experimental mass as input and obtain the width of the state and the (DD0 pi-)-D-0+ mass distribution. When the mass of the T-cc state quoted in the experimental paper from raw data is used, the width obtained is of the order of the 80 keV, small compared to the value given in that work. Yet, when the mass obtained in an analysis of the data considering the experimental resolution is taken, the width obtained is about 43 keV and both the width and the (DD0 pi+)-D-0 mass distribution are in remarkable agreement with the results obtained in that latter analysis.
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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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Jiang, S. J., Sakai, S., Liang, W. H., & Oset, E. (2019). The chi c J decay to phi K*(K)over-bar, phi h(1)(1380) testing the nature of axial vector meson resonances. Phys. Lett. B, 797, 134831–5pp.
Abstract: We perform a theoretical study of the chi(cJ) -> phi K*(K) over bar -> phi K pi(K) over bar reaction taking into account the K*(K) over bar final state interaction, which in the chiral unitary approach is responsible, together with its coupled channels, for the formation of the low lying axial vector mesons, in this case the h(1)(1380) given the selection of quantum numbers. Based on this picture we can easily explain why in the chi(c0) decay the h(1)(1380) resonance is not produced, and, in the case of chi(c1) and chi(c2) decay, why a dip in the K+ pi K-0(-) mass distribution appears in the 1550-1600 MeV region, that in our picture comes from a destructive interference between the tree level mechanism and the rescattering that generates the h(1)(1380) state. Such a dip is not reproduced in pictures where the nominal h(1)(1380) signal is added incoherently to a background, which provides support to the picture where the resonance appears from rescattering of vector-pseudoscalar components.
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