Tamotsu Ueda

N̄N annihilation at low energies in a quark rearrangement model and decay widths of N̄N bound states

Abstract Using NN annihilation data at rest, we make a quark rearrangement model for annihilation into three mesons. This model describes the decay branching ratios of the pp and pn annihilations at rest satisfactorily. With this model we find considerable dependence of the annihilation on the isospin and spin of the initial NN system. By calculating the energy dependence due to the phase space of three mesons, we extend the model in the energy range E c.m. . = 1400 MeV –2300 MeV where E c.m. is the total energy in the c.m.s. We find the strong energy dependence of the annihilation, with the annihilation probability below the NN threshold reduced drastically, compared to that at threshold. Based on the result for the quantum number and energy dependence, we discuss the possibility of the existence of NN bound states with narrow decay widths.

Dibaryon resonances in πNN dynamics

Abstract The pp 3 F 3 resonance is explained as a resonance of the πNN system where π makes Δ with both nucleons in the 3 P 2 state. A similar mechanism causes also four quasi-bound states of I = 1 and 2 πNN systems with J P = 2 + , J P = 1 + and mass 2.14–2.18 GeV.

Dibaryon resonances in πNN and ππNN dynamics

Abstract Dibaryon resonances are predicted in the mechanism that the sum of the nuclear force and the attractive force caused by two nucleons keeping in common one or two real pions in the Δ state generates πNN and ππNN resonances.

The pole structure of the 1D2 and 3F3 NN-amplitudes in the Faddeev πNN dynamics

Abstract The strong energy-dependent structures in the 3F3 and 1D2 pp-phase parameters are explained as a manifestation of the pole structures of the NN amplitudes generated by the Faddeev πNN dynamics.

πNN dynamics and the 3F3 diproton anomaly appearing in pp-pp, pp-πd and πd-πd processes

Abstract A three-body calculation of πNN systems with I = 1 and J P = 3 − is made in the energy range of the incident proton laboratory energies T L = 400–1400 MeV. We use a semi-relativistic formulation where a pion is relativistic and two nucleons are non-relativistic, and assume two-body potentials as input of πN-P 11 , πN-P 33 , NN- 3 P 2 and NN- 3 S 1 interactions. Three different πN-P 33 interactions are employed which are phase-equivalent up to 400 MeV of the incident pion laboratory energy, but differ from each other in the off-shell structure. The result is compared with partial-wave analysis results of pp-pp, pp-πd and πd-πd processes. Concerning the 3 F 3 diproton anomaly we find that the theoretical result depends largely on the off-shell structure of the πN-P 33 interaction. With a reasonable choice of the πN-P 33 interaction the pp- 3 F 3 diproton anomaly, appearing in the phase-shift analysis result, is approximately reproduced, and simultaneously we obtain a result which is qualitatively consistent with the partial-wave analysis results of pp-πd and πd-πd processes within the uncertainty of the analyses.

NN-scattering at 400–1000 MeV in OBE-πNN dynamics and dibaryons

Abstract Including the 1 D 2 and 3 F 3 dibaryon anomalies, NN scattering below 1 GeV is likely to be described in terms of OBE- π NN dynamics.

A quark rearrangement model with spatial overlap function for low energy NN annihilation

Abstract The major part of the branching ratios for the N N annihilation at rest is explained by the quark rearrangement in the N and N into three SU(6) mesons. This is shown by using the spin, isospin, and spatial overlap function derived theoretically from quark dynamics.

Three-nucleon interactions and nuclear matter

Abstract We derive the three-nucleon potentials due to π, S (isoscalar-scalar-meson) and ω, which are exchanged between two nucleons via the third nucleon. The off-mass-shell πN amplitude needed for the calculation is constructed on the basis of the chiral invariance and the πN scattering data. Uncertainties caused by the uncertainties inherent in boson-vertices are considerably reduced by requiring that the three-nucleon potentials due to S and ω become the same as the one-S and one-ω exchange two-nucleon potentials, respectively, if the interactions of S and ω with the third nucleon are switched off. We calculate the binding energy per nucleon in nuclear matter using the three-nucleon potentials thus obtained with the two-nucleon OBEP of Ueda and Green (UGI), and find 0.4, 4.3 and −1. 3MeV at k F = 1.4 fm −1 for the net contributions from the three-nucleon potentials due to π, S and ω, respectively. The sum of the two- and three-nucleon potentials gives approximately correct binding energy at the normal density. However, its density dependence is such that it produces overbinding at higher density. A suggestion for removing this difficulty is made.

Elastic and inelastic nucleon-nucleon scatterings in the πNN dynamics

Abstract pp-pp, np-np, pp- π + d and pp- π + pn processes are studied in a unitary model of the πNN dynamics in a unified way. The origin for the anomalous phenomena in the J P =2 + and 3 − channels is clarrified.

Off-shell structure of the πN-P33 interaction and its effect on the NN 3F3 phase parameter

Abstract The large off-shell freedom of the πN-P33 interaction is pointed out and also its remarkable effect on the anomalous pp-3F3 phase parameter in the πNN dynamics. A correspondence with the NN-NΔ transition potential is also made.