K. Itonaga

Pi-mesonic decay of light Λ-hypernuclei

Abstract The π-mesonic decays of all p-shell Λ hypernuclei are studied using the shell model combined with density-dependent Hartree-Fock wavefunctions. The pion distortion is taken into account by using the optical potential. The summed decay rate of π0 and π− decays decreases with the mass number A, while each decay rate (Γπ0, Γπ−) exhibits a non-trivial and characteristic variation with A, reflecting the shell-structure effects. Among the π-mesonic decay partial rates some strong transition strengths are seen in, for example, π− decays of 9ΛLi and 9ΛBe and π0 decay of 12ΛC. Large-asymmetric pion angular patterns are predicted in π− decays from the polarized hypernuclei such as 8ΛLi(1−), 8ΛBe(1−) and 9 Λ Be( 1 2 + ) .

Four-Hole Structure in Fe Isotopes

Four-hole correlations seen in the Fe isotopes (A=52, 53, 54) are systematically inves· tigated in the framework of the shell model. The structure of the correlated four-holes in the 1f,1, orbit is understood as the cooperative interplay of the important pairing plus T=O, J!ru..x=7+ correlations and T=1, J=2+ correlations. The coupling scheme is very similar to the stretch-coupling one. Correlated four-holes changes its structure gradually when a few particles are added to it. However the weak-coupling-like features are seen for the lowest series of 4 hole-n particle states. The states of other types of configurations in the Fe isotopes are well reproduced. Renormalization techniques are employed for such physical quantities as the single particle energy, the hole-hole interaction and the particle-hole interaction.

pi-Mesonic decay of hypernuclei and pion wavefunction

The pi-mesonic decay of hypernuclei is studied by using the pion distorted waves which are the solutions of the Klein-Gordon equation with the optical potential. The distortions of the pion waves give rise to significant enhancement of theπ-decay rate compared with the pion free-wave case. Theπ-decay rates are very sensitive to the behavior of the pion wave deep inside the nucleus and therefore to the chosen pion optical potentials. There is a tendency that the enhancement is larger for theπ−-decay than for theπ0-decay due to the combined effects of the Coulomb and optical potentials.

Spectroscopy of Σ9Be

Shell-model calculation of Σ 9 Be structure is performed and the result is compared to the data from (K−, π−) experiment.

Pions in nuclear interior — sensitive test by hypernuclear decay

The effect of the pion wave distortion on the pi-mesonic weak decay ofΛ-hyperon in hypernuclei is studied by using two different pion optical potentials, one by Gmitro, Kamalov and Mach, which is given in momentum space, and the other by MSU group, which is in the standard Kisslinger form. The two potentials lead to a striking difference in the pi-mesonic decay, reflecting different behaviors of the pion wavefunctions deep inside the nucleus.

Polarization in P-Shell Λ-Hypernuclear Productions

The hypernuclear production by (π +, K +) and (K −, π −) reactions and its polarization of produced states are studied on p-shell targets by using the spin-nonflip and spin-flip amplitudes of the elementary process. The hypernuclear polarization and Λ-spin polarization in the hypernuclear states are discussed in accordance with their subsequent decay process.

Heavy Ion Cllision with Friction Model

16 0+ 16 0 collisions at intermediate energies. The fusion window appears for ECM=80 MeV. The temperature of 16 0 can reach ~4.5 (4.0) MeV for ECM=160 (80) MeV, when the heavy ion potential evaluated by using the density· dependent nucleon-nucleon interaction and the chosen friction coefficients estimated with the potential are employed in the equations. The time evolution of the nuclear temperature is obtained consistently with the damping of the relative motion. Important ingredients that control the heavy ion trajectories are discussed.