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Toledo, G., Ikeno, N., & Oset, E. (2021). Theoretical study of the D-0 -> K-pi(+)eta reaction. Eur. Phys. J. C, 81(3), 268–11pp.
Abstract: We develop a model to study the D-0 -> K-pi(+)eta weak decay, starting with the color favored external emission and Cabibbo favored mode at the quark level. A less favored internal emission decay mode is also studied as a source of small corrections. Some pairs of quarks are allowed to hadronize producing two pseudoscalar mesons, which posteriorly are allowed to interact to finally provide the K-pi(+)eta state. The chiral unitary approach is used to take into account the final state interaction of pairs of mesons, which has as a consequence the production of the kappa (K-0*(700)) and the a(0)(980) resonances, well visible in the invariant mass distributions. We also introduce the (K) over bar*(0)eta production in a phenomenological way and show that the s-wave pseudoscalar interaction together with this vector excitation mode are sufficient to provide a fair reproduction of the experimental data. The model provides the relative weight of the a(0)(980) to the kappa excitation, and their strength is clearly visible in the low energy part of the K pi spectrum.
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Tani, A., Ikeno, N., Jido, D., Nagahiro, H., Fujioka, H., Itahashi, K., et al. (2021). Structure of double pionic atoms. Prog. Theor. Exp. Phys., 2021(3), 033D02–16pp.
Abstract: We study theoretically the structure of double pionic atoms, in which two negatively charged pions (pi(-)) are bound in the atomic orbits. The double pionic atom is considered to be an interesting system from the point of view of the multi-bosonic systems. In addition, it could be possible to deduce valuable information on the isospin I = 2 pi pi interaction and the pionnucleus strong interaction. In this paper, we take into account the pi pi strong and electromagnetic interactions, and evaluate the effects on the binding energies by perturbation theory for the double pionic atoms in heavy nuclei. We investigate several combinations of two pionic states and find that the order of magnitude of the energy shifts due to the pi pi interaction is around 10 keV for the strong interaction and around 100 keV for the electromagnetic interaction for the ground states.
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Molina, R., Ikeno, N., & Oset, E. (2023). Sequential single pion production explaining the dibaryon “d*(2380)” peak. Chin. Phys. C, 47(4), 041001–10pp.
Abstract: In this study, we investigate the two step sequential one pion production mechanism, that is, np(I=0)->pi(-)pp followed by the fusion reaction pp ->pi(+)d, to describe the np ->pi(+)pi(-)d reaction with in state I = 0 . In this reaction, a narrow peak identified with a “ d(2380) ” dibaryon has been previously observed. We discover that the second reaction step pp ->pi(+)d is driven by a triangle singularity that determines the position of the peak of the reaction and the high strength of the cross section. The combined cross section of these two mechanisms produces a narrow peak with a position, width, and strength, that are compatible with experimental observations within the applied approximations made. This novel interpretation of the peak accomplished without invoking a dibaryon explains why this peak has remained undetected in other reactions.
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Liang, W. H., Ikeno, N., & Oset, E. (2020). Upsilon(nl) decay into B(*) (B)over-bar(*). Phys. Lett. B, 803, 135340–6pp.
Abstract: We have evaluated the decay modes of the Upsilon(4s), Upsilon(3d), Upsilon(5s), Upsilon(6s) states into B (B) over bar, B (B) over bar* + c.c., B* (B) over bar*, B-s(B) over bar (s), B-s(B) over bar (s)* + c.c., B-s* (B) over bar (s)* using the P-3(0) model to hadronize the bb vector seed, fitting some parameters to the data. We observe that the Upsilon(4s) state has an abnormally large amount of mesonmeson components in the wave function, while the other states are largely b (b) over bar. We predict branching ratios for the different decay channels which can be contrasted with experiment for the case of the Upsilon(5s) state. While globally the agreement is fair, we call the attention to some disagreement that could be a warning for the existence of more elaborate components in the state.
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Ikeno, N., Bayar, M., & Oset, E. (2018). Semileptonic decay of B-c(-) into X (3930), X (3940), X (4160). Eur. Phys. J. C, 78(5), 429–7pp.
Abstract: We study the semileptonic decay of B-c(-) meson into & Unknown;l(-) and the isospin zero X (3930) (2(++)), X(3940) (0(++)), X (4160) (2(++)) resonances. We look at the reaction from the perspective that these resonaces appear as dynamically generated from the vector-vector interaction in the charm sector, and couple strongly to D*& Unknown;D* and D-s*& Unknown;D-s*. We also look into the B-c(-) -> & Unknown;(l)l(-) D*& Unknown;* and B-c(-) -> & Unknown;(l)l(-) D-s*& Unknown;(s)* reactions close to threshold and relate the D*& Unknown;* and D-s*& Unknown;(s)* mass distribution to the rate of production of the X resonances.
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Ikeno, N., Dai, L. R., & Oset, E. (2020). Meson exchange between initial and final state and the R-D ratio in the B-bar -> D nu-bar l (nu_tau-bar tau) reactions. Eur. Phys. J. A, 56(2), 73–12pp.
Abstract: We perform a calculation of the strong interaction effects between the B and D mesons in the B -> D nu l reaction, as a crossing process of reactions with BD in the final state, where the strong interaction between the mesons leads to a bound BD state. We find corrections to the tree level amplitude of the order of 15-25%. We further see the effect of the corrections studied in the R-D ratio for the rates of B -> D nu and B. D decays and find corrections of the order of 10%. Given the claims of 1.5% precision in this ratio from fits to data within the standardmodel, any theoretical model aiming at describing this ratio within the same precision must take into account the corrections described in the present work.
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Ikeno, N., Liang, W. H., & Oset, E. (2024). Molecular nature of the Ωc(3120) and its analogy with the Ω(2012). Phys. Rev. D, 109(5), 054023–7pp.
Abstract: We make a study of the omega c(3120) , one of the five omega c states observed by the LHCb Collaboration, which is well reproduced as a molecular state from the Xi*cK over bar and omega*c17 channels mostly. The state with JP = 3/2- decays to Xi cK over bar in the D wave, and we include this decay channel in our approach, as well as the effect of the Xi*c width. With all these ingredients, we determine the fraction of the omega c(3120) width that goes into Xi cK over bar K , which could be a measure of the Xi*cK over bar molecular component, but due to a relatively big binding, compared to its analogous omega(2012) state, we find only a small fraction of about 3%, which makes this measurement difficult with present statistics. As an alternative, we evaluate the scattering length and effective range of the Xi*c K over bar and omega*c17 channels, which, together with the binding and width of the omega c(3120) state, could give us an answer to the issue of the compositeness of this state when these magnitudes are determined experimentally, something feasible nowadays, for instance, measuring correlation functions.
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Ikeno, N., Toledo, G., & Oset, E. (2020). Molecular picture for the Omega(2012) revisited. Phys. Rev. D, 101(9), 094016–9pp.
Abstract: We conduct a study of the interaction of the (K) over bar Xi*, eta Omega(s-wave), and (K) over bar Xi(d-wave) channels within a coupled channel unitary approach where the transition potential between the (K) over bar Xi* and eta Omega channels is obtained from chiral Lagrangians. The transition potential between (K) over bar Xi*, eta Omega, and (K) over bar Xi is taken in terms of free parameters, which together with a cutoff to regularize the meson-baryon loops are fitted to the Omega(2012) data. We find that all data including the recent Belle experiment on Gamma(Omega*->pi(K) over bar Xi)/Gamma(Omega*->(K) over bar Xi), are compatible with the molecular picture stemming from meson baryon interaction of these channels.
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Ikeno, N., Molina, R., & Oset, E. (2021). The Z(cs)(3985) as a threshold effect from the (D)over-bar(s)*D + (D)over-bar(s)D* interaction. Phys. Lett. B, 814, 136120–5pp.
Abstract: We study the e(+)e(-) -> K+(D-s*D--(0) + Ds-D*(0)) reaction recently measured at BESIII, from where a new Z(cs) state has been reported. We study the interaction of (D) over bar D-s* with the coupled channels J/psi K-, K*(-)eta(c), Ds-D*(0), D-s*D--(0) by means of an extension to the charm sector of the local hidden gauge approach. We find that the Ds-D*(0) + D-s*D--(0) combination couples to J/psi K- and K*(-)eta(c), but the Ds-D*(0 ) -D-s*D--(0) combination does not. The coupled channels help to build up strength in the Ds-D*(0) + D-s*D--(0) diagonal scattering matrix close to threshold and, although the interaction is not strong enough to produce a bound state or resonance, it is sufficient to produce a large accumulation of strength at the (D) over bar D-s* threshold in the e(+)e(-) -> K+(D-s*D--(0) + Ds-D*(0)) reaction in agreement with experiment.
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Ikeno, N., Molina, R., & Oset, E. (2021). Triangle singularity mechanism for the pp -> pi(+)d fusion reaction. Phys. Rev. C, 104(1), 014614–16pp.
Abstract: We develop a model for the pp -> pi(+)d reaction based on the pp -> Delta(1232)N transition followed by Delta(1232) -> pi N' decay and posterior fusion of NN' to give the deuteron. We show that the triangle diagram depicting this process develops a triangle singularity leading to a large cross section of this reaction compared to ordinary fusion reactions. The results of the calculation also show that the process is largely dominated by the pp system in L = 2 and S = 0, which transfers J = 2 to the final pi(+)d system. This feature is shown to be well suited to provide L = 2, S = 1, and J(tot) = 3 for np in the np(I = 0) pi(-)pp reaction followed by the pp -> pi(+)d reaction, which has been proposed recently, as a means of describing the so far assumed dibaryon d* (2380) peak.
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