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Molina, R., Liang, W. H., Xiao, C. W., Sun, Z. F., & Oset, E. (2024). Two states for the Ξ(1820) resonance. Phys. Lett. B, 856, 138872–4pp.
Abstract: We recall that the chiral unitary approach for the interaction of pseudoscalar mesons with the baryons of the decuplet predicts two states for the Xi(1820) resonance, one with a narrow width and the other one with a large width. We contrast this fact with the recent BESIII measurement of the K- Lambda mass distribution in the psi(3686) decay to K- Lambda Xi(+), which demands a width much larger than the average of the PDG, and show how the consideration of the two Xi(1820) states provides a natural explanation to the experimental data.
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Feng, Y. C., Gil, F., Döring, M., Molina, R., Mai, M., Shastry, V., et al. (2024). Unitary coupled-channel three-body amplitude with pions and kaons. Phys. Rev. D, 110(9), 094002–21pp.
Abstract: Three-body dynamics above threshold is required for the reliable extraction of many amplitudes and resonances from experiment and lattice QCD. The S-matrix principle of unitarity can be used to construct dynamical coupled-channel approaches in which three particles scatter off each other, rearranging two-body subsystems by particle exchange. This paper reports the development of a three-body coupled-channel, amplitude including pions and kaons. The unequal-mass amplitude contains two-body S- and P-wave subsystems (“isobars”) of all isospins, I = 0, 1/2, 1,3/2, 2, and it also allows for transitions within a given isobar. The f 0 ( 500 )( 6 ) ,f 0 ( 980 ) , p ( 700 ) ,K * 0 ( 700 )( K ) , and K * ( 892 ) resonances are included, apart from repulsive isobars. Different methods to evaluate the amplitude for physical momenta are discussed. Production amplitudes for a 1 quantum numbers are shown as a proof of principle for the numerical implementation.
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Aceti, F., Molina, R., & Oset, E. (2012). X(3872) -> J/psi gamma decay in the D(D)over-bar* molecular picture. Phys. Rev. D, 86(11), 113007–13pp.
Abstract: From a picture of the X(3872) where the resonance is a bound state of D (D) over bar*- c.c., we evaluate the decay width into the J/psi gamma channel, which is sensitive to the internal structure of this state. For this purpose we evaluate the loops through which the X(3872) decays into its components, and the J/psi and the photon are radiated from these components. We use the local hidden gauge approach extrapolated to SU(4) with a particular SU(4) breaking. The radiative decay involves anomalous couplings, and we obtain acceptable values which are compared to experiments and results of other calculations. Simultaneously, we evaluate the decay rate for the X(3872) into J/psi omega and J/psi rho, and the results obtained for the ratio of these decay widths are compatible with the experiment. We also show that considering only the (D) over bar D-0*(0) – c.c. component in the radiative decay reduces the partial decay width in more than three orders of magnitude, in large discrepancy with experiment.
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Ikeno, N., Molina, R., & Oset, E. (2022). Zcs states from the D*s over bar D* and J=psi K* coupled channels: Signal in B+ -> J=psi phi K+ decay. Phys. Rev. D, 105(1), 014012–13pp.
Abstract: We study the D*s over bar D* system in connection with the J=psi K* in coupled channels and observe that, within reasonable values of the cutoff used to regularize the loops, the system does not develop a bound state. However, the JP = 2+ channel has enough attraction to create a strong cusp structure that shows up in the J=psi K+ invariant mass distribution in the B+ -> J=psi phi K+ decay at the D*s over bar D* threshold. Such structure is results should stimulate further measurements around this region, given the fact that cusp effects provide as valuable information on hadron dynamics as resonances themselves.
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Liang, W. H., Molina, R., & Oset, E. (2024). Ωc→π+(π0, η)πΞ*, π+(π0, η)K¯Σ* reactions and the two Ξ(1820) states. Phys. Rev. D, 110(3), 036005–9pp.
Abstract: We have studied the Omega c-* pi+(pi 0, + ( pi 0 , eta)pi Xi ) pi Xi and Omega c-* pi+(pi 0, + ( pi 0 , eta ) K Sigma decays, where the final pi Xi Xi or K Sigma Sigma comes from the decay of two resonances around the nominal Xi ( 1820 ) , which are generated from the interaction of coupled channels made of a pseudoscalar and a baryon of the decuplet. The pi Xi Xi mass distributions obtained in the six different reactions studied are quite different, and we single out four of them, which are free of a tree level contribution, showing more clearly the effect of the resonances. The lower mass resonance is clearly seen as a sharp peak, but the higher mass resonance manifests itself through an interference with the lower one that leads to a dip in the mass distribution around 1850 MeV. Such a feature is similar to the dip observed in the S- wave pi pi cross section around the 980 MeV coming from the interference of the f 0 ( 500 ) and f 0 ( 980 ) resonances. Its observation in coming upgrades of present facilities will shed light on the existence of these two resonances and their nature. On the other hand, when the Omega c-* pi+(pi 0, + ( pi 0 , eta ) K Sigma reactions are studied, both peaks are observed.
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