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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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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Ikeno, N., Bayar, M., & Oset, E. (2021). Combined theoretical study of the D+ -> pi(+) eta eta and D+ -> pi(+)pi(0) eta reactions. Eur. Phys. J. C, 81(4), 377–10pp.
Abstract: We study the D+ -> pi(+) eta eta and D+ -> pi(+)pi(0) eta reactions, which are single Cabibbo suppressed and can proceed both through internal and external emission. The primary mechanisms at quark level are considered, followed by hadronization to produce three mesons in the D+ decay, and after that the final state interaction of these mesons leads to the production of the a(0)(980) resonance, seen in the pi(+)eta, pi(0)eta mass distributions. The theory has three unknown parameters to determine the shape of the distributions and the ratio between the D+ -> pi(+) eta eta and D+ -> pi(+)pi(0) eta rates. This ratio restricts much the sets of parameters but there is still much freedom leading to different shapes in the mass distributions. We call for a measurement of these mass distributions that will settle the reaction mechanism, while at the same time provide relevant information on the way that the a(0)(980) resonance is produced in the reactions.
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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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Ikeno, N., Liang, W. H., Toledo, G., & Oset, E. (2022). Interpretation of the Omega(c) -> pi(+) Omega(2012) -> pi(+) ((K)over-bar Xi) relative to Omega(c) -> pi(+) (K)over-bar Xi from the Omega (2012) molecular perspective. Phys. Rev. D, 106(3), 034022–10pp.
Abstract: We present a mechanism for Omega(c) -> pi(+)Omega (2012) production through an external emission Cabibbo favored weak decay mode, where the Omega (2012) is dynamically generated from the interaction of (K) over bar Xi(*) (1530) and eta Omega, with (K) over bar Xi as the main decay channel. The Omega (2012) decays later to (K) over bar Xi. in this picture, with results compatible with Belle data. As a consequence, one can evaluate the direct decay Omega(0)(c) -> pi K-+(-)Xi(0) and the decay Omega(0)(c) -> pi(+)(K) over bar Xi* pi(+)eta Omega with direct couplings of (K) over bar Xi* and eta Omega to K-Xi(0). We show that, within uncertainties and using data from a recent Belle measurement, all three channels account for about (12-20)% of the total Omega(c) -> pi K-+(-)Xi(0) decay rate. The consistency of the molecular picture with all the data is established by showing that Omega(c) -> Xi(0)(K) over bar*(0) -> Xi K-0(-)pi(+) and Omega(c) -> pi(+)Omega* -> pi K-+(-Xi 0) account for about 85% of the total Omega(c) -> pi K-+(-)Xi(0).
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