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Bayar, M., Molina, R., Oset, E., Liu, M. Z., & Geng, L. S. (2024). Subtleties in triangle loops for Ds+ → ρ+ η → π+ π0 η in a0(980) production. Phys. Rev. D, 109(7), 076027–7pp.
Abstract: We address a general problem in the evaluation of triangle loops stemming from the consideration of the range of the interaction involved in some of the vertices, as well as the energy dependence of the width of some unstable particles in the loop. We find sizeable corrections from both effects. We apply that to a loop relevant to the D + s -> pi + pi 0 eta decay, and find reductions of about a factor of 4 in the mass distribution of invariant mass of the pi eta in the region of the a 0 ( 980 ) . The method used is based on the explicit analytical evaluation of the q 0 integration in the d 4 q loop integration, using Cauchy 's residues method, which at the same time offers an insight on the convergence of the integrals and the effect of form factors and cutoffs.
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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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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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Gil-Domínguez, F., Giachino, A., & Molina, R. (2025). Quark mass dependence of the Tcc(3875) + pole. Phys. Rev. D, 111(1), 016029–21pp.
Abstract: Recently, several LQCD simulations have proven that the interaction in the isoscalar channel in DD* scattering is attractive. This channel is naturally connected to the Tcc(3875)+ which is observed in the D0D0,c+ invariant mass distribution. However, it remains an open question whether the virtual bound state found in these several LQCD simulations is actually linked to the LHCb experimental observation. In this article we perform an EFT-based analysis of the LQCD data and demonstrate that a proper chiral extrapolation leads to a Tcc pole compatible with experiment. At the physical pion mass, we find a virtual bound state with a binding energy Delta E = -0.06(+1.30 -2.20)(+0.5-1.110).Moreover, we extract from a global analysis both the light and heavy quark mass dependence of the Tcc pole and study the role of the p- and i-meson exchanges.
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Zhai, Q. Y., Molina, R., Oset, E., & Geng, L. S. (2025). Study of the exotic three-body ND*Kbar* system. Phys. Rev. D, 111(3), 034039–6pp.
Abstract: We have studied the ND*K<overline>* system in the framework of the fixed center approximation to the Faddeev equations, taking the exotic D*K<overline>* system as the cluster and allowing the N to interact with the components of the cluster. Previous studies have determined the existence of three states of spin 0, 1, 2 for the D*K<overline>* system, the one of spin 0 associated to the X0(2900) state observed by the LHCb Collaboration. From this perspective, we find five states with total spin 1/2, 3/2, 5/2, with bindings from 10 to 30 MeV and widths below 60 MeV, which could be well identified. We also discuss the decay channels of these states that should help in future experimental searches for these states.
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Shi, P. P., Gil-Dominguez, F., Molina, R., & Du, M. L. (2025). Pole analysis for the D*K-DK* coupled-channel system. Phys. Lett. B, 868, 139699–8pp.
Abstract: By solving the Lippmann-Schwinger equation, possible hadronic molecules in the D*K-DK* coupled-channel system are investigated with the one-meson exchange potentials, where both vector and pseudoscalar mesons are considered as exchange particles. We find an S-wave virtual state with mass M = 2487 MeV, and a resonance with M = 2759 and width Gamma= 18 MeV. In the D*K invariant mass distribution, the virtual state appears as a cusp at the D*K threshold, while the resonance potentially manifests as a dip. In particular, we take into account the DK pi three-body dynamics due to the on-shell pion exchange and the finite decay width for K*.
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Zhuang, Z. J., Molina, R., Lu, J. X., & Geng, L. S. (2025). Pole trajectories of the A 1405 help establish its dynamical nature. Sci. Bull., 70(12), 1953–1961.
Abstract: The A 1405 has been one of the most controversial exotic baryons. If the A 1405 possesses a two-pole molecular structure, these poles are expected to evolve differently towards the SU(3) limit. From an analysis of a recent LQCD simulation on the pi Sigma -(K) over barN scattering for I 0 and the study of the quark mass dependence of the octet baryon masses, we determine for the first time the trajectories of these poles towards the symmetric point over the Tr[M] = C trajectory accurately. At m(pi) similar or equal to 200 MeV, our results are consistent with the lattice simulations, and the extrapolations to the physical point, based on the NLO chiral Lagrangians, agree well with existing experimental analyses. We predict qualitatively similar trajectories at LO and up to NLO, consistent with the LO interaction's dominance. At the SU(3) symmetric point of this trajectory, both poles are on the physical sheet, and the lower pole is located at E(1) =1573(6)(6) MeV, becoming a SU(3) singlet, while the higher pole at E ((8a)) = 1589 (7) (5) MeV couples to the octet representation. Moreover, we make predictions in I = 1 for the E resonance. We find a resonance pole that evolves into a bound state around m(pi) = 415 MeV in this sector. The results presented here are crucial to shed light on the molecular nature of exotic strange baryon resonances and can be tested in future LQCD simulations.
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Li, Y. Y., Song, J., Oset, E., Liang, W. H., & Molina, R. (2025). The Λc plus →Λπ plus π plus π- reaction, and a triangle singularity producing the Σ* state. Eur. Phys. J. C, 85(9), 1086–12pp.
Abstract: We study the decay Lambda c+->Lambda pi+pi+pi-, focusing on the production of the Sigma*(1430) resonance observed by the Belle Collaboration. Interpreted as a dynamically generated state from meson-baryon interactions in the chiral unitary approach, the Sigma*(1430) signal is shown to be enhanced by a triangle singularity involving intermediate K*-, p, and K0 states. This mechanism leads to a sharp peak near 1434 MeV in the pi+Lambda invariant mass distribution, in agreement with the experimental observations, and predicts a secondary peak around 1875 MeV in the pi-Sigma*(1430) spectrum tied to the triangle singularity. We also estimate the branching ratio of Lambda c+->pi+pi-Sigma*(1430) to be about 3.5x10-4. The results for the branching ratio and the pi-Sigma*(1430) mass distributions are predictions of the theoretical approach, which could be tested with reanalysis of existing data.
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