Seigo Kato

Experimental determination of the Ne-19(p, gamma)Na-20 reaction rate and the breakout problem from the hot CNO cycle

The nuclear levels of Na-20 are studied experimentally using the (He-3, t) and (p, n) reactions on Ne-20. The spin parities and excitation energies are determined for the states near and above the p + Ne-19 threshold. The stellar reaction rate of the Ne-19(p, gamma) process is evaluated based on the data. The calculation shows a more than two orders of magnitude larger rate than the previous theoretical predictions. The finding of s-wave resonance just above the capture threshold may change the onset temperature of breakout from the CNO cycle and explains the strong enhancement of Ne and heavier elements in observations of nova V1370 Aql 1982. 16 refs.

A broad range spectrometer PIK for medium-energy meson spectroscopy

Abstract A broad range spectrometer, PIK, has been constructed for the study of Λ hypernuclei via the ( π + , K + ) reaction. The spectrometer can also be used for nuclear spectroscopy with medium-energy meson beams. It consists of two independent spectrometers: one analyzes the incident beam momentum, and the other determines the momentum of the scattered particle. The latter spectrometer is characterized by a large solid angle of 15–22 msr, a broad range momentum acceptance of 0.55–1.1 GeV/ c , a wide angular acceptance of 11°, and a short flight path length of 4.5 m. The scattered particle is identified by the use of silica aerogel Cherenkov counters and Lucite Cherenkov counters and by measuring its time-of-flight. The performance of the spectrometer is examined by the ( π + , K + ) reaction on a 12 C target at P π = 1.05 GeV/ c and by the ( π + , p) reaction on a CH 2 target.

Trojan Horse method and radioactive ion beams: Study of 18F(p,α)15O reaction at astrophysical energies

The Trojan Horse Method was applied for the first time to a Radioactive Ion Beam induced reaction to study the reaction 18F(p,α)15O via the three body reaction 18F(d,α 15O)n at the low energies relevant for astrophysics. The abundance of 18F in Nova explosions is an important issue for the understanding of this astrophysical phenomenon. For this reason it is necessary to study the nuclear reactions that produce or destroy 18F in Novae. 18F(p,α)15O is one of the main 18F destruction channels. Preliminary results are presented in this paper.

Kaon, pion, and proton associated photofission of Bi nuclei

The first measurement of proton, pion, and kaon associated fission of Bi nuclei has been performed in a photon energy range 1. 45 < Eγ < 1. 55 GeV. The fission probabilities are compared with an inclusive fission probabilities obtained with photons, protons and pions. The fission probability of Bi nuclei in coincidence with kaons is 0. 18 ± 0. 06 which is ∼3 times larger than the proton and pion associated fission probabilities and ∼2 times larger than inclusive ones. The kaon associated excess fission events are explained in terms of bound Λ residual states and their weak nonmesonic decays.

Angular Distribution for the Reaction 16O(p, t)14O* (6.27 MeV) and Channel Coupling Effects

Angular distribution for the 16 O( p , t ) 14 O * (6.27 MeV) reaction obtained at E p =52 MeV has confirmed a previous observation that it cannot be fitted by L =3 DWBA. An explanation in terms of couple-channel Born approximation is presented.

Proton-rich sd-shell nuclei for astrophysical interest

Abstract Experimental study of proton rich sd-shell nuclei, especially the nuclei which locate on the breakout processes of Hot-CNO cycle and NeNa cycle, i.e., 20 Na and 24 Al are discussed. Considerable level shifts are observed in the 24 Al levels, including some new states above the proton threshold. The previous reaction rate of 23 Mg(p,γ) 24 Al was found to be underestimated more than 80 %. The result indicates an importance of the experiment for the sd-shell proton-rich nuclei for the astrophysical interest.

Observation of the Lowest T=2 State in 24Al through the 27Al(3He,6He)24Al Reaction

The lowest T=2 state in 24 Al was observed through the 27 Al( 3 He, 6 He) 24 Al rection. The mass excess (5.919±0.010 MeV) of the state supports the quadratic form of the isobaric multiplet mass equation.