M. Segawa

62Ni(n, γ)63Ni Reaction and Overproduction of Ni Isotopes

The neutron capture cross section of 62Ni has been measured in the energy range from 5.5 to 90 keV by employing a prompt discrete γ-ray detection method with the use of an anti-Compton NaI(Tl) spectrometer. The Maxwellian-averaged capture cross section at 30 keV is derived as being 37.0 ± 3.2 mbarn, 3 times larger than the value currently used for the nucleosynthetic yield estimations in massive stars. The result could provide crucial information for the long-standing problem of the largest overproduction of 62Ni. The intense discrete γ-ray feeding from a neutron capture state to the ground state of 63Ni was for the first time observed at stellar neutron energy. This observation and the neutron energy dependence of the total neutron capture cross section of 62Ni indicate clearly that the dominant capture process of 62Ni is a nonresonant direct s-wave capture process and not a p-wave capture process as previously predicted.

Differential cross section and analyzing power of the p → p → pp π 0 reaction at a beam energy of 390 MeV

Y. Maeda, 2, ∗ M. Segawa, † T. Ishida, ‡ A. Kacharava, M. Nomachi, Y. Shimbara, § Y. Sugaya, K. Tamura, T. Yagita, K.Yasuda, H.P.Yoshida, ¶ and C. Wilkin Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan Institut für Kernphysik, Forschungszentrum Jülich, 52425 Jülich, Germany Department of Physics, Kyushu University, Fukuoka 812-8581, Japan High Energy Physics Institute, Tbilisi State University, 0186 Tbilisi, Georgia Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan Physics Division, Fukui Medical University, Fukui 910-1193, Japan The Wakasa Wan Energy Research Center, Fukui 914-0192, Japan Physics and Astronomy Department, UCL, Gower Street, London WC1E 6BT, United Kingdom (Dated: May 11, 2010)

Differential cross section and analyzing power of the p-vectorp{yields}pp{pi}{sup 0} reaction at a beam energy of 390 MeV

The differential cross section and analyzing power A{sub y} of the p-vectorp{yields}pp{pi}{sup 0} reaction have been measured at RCNP in coplanar geometry at a beam energy of 390 MeV and the dependence on both the pion emission angle and the relative momentum of the final protons has been extracted. The angular variation of A{sub y} for the large values of the relative momentum studied here shows that this is primarily an effect of the interference of pion s and p waves and this interference can also explain the momentum dependence. Within the framework of a very simple model, these results would suggest that the pion-production operator has a significant long-range component.

Probing universe with fast neutrons

Fast neutrons play crucial roles as a probe to trace the history of the universe. The present paper describes our recent work on the measurement of the neutron capture and neutron inelastic scattering cross sections of various nuclei from primordial and stellar nucleostyntheses point of view, which have been carried out by developing a high sensitive measurement system. The obtained results are compared to previous works and theoretical calculations.

Preparation for the 12C(α,γ)16O experiment using pulsed α beam

Abstract We have installed a new experiment system to measure the 12 C(α,γ) 16 O reaction cross section accurately below E cm = 1.75 MeV. Using the system, we will also measure the γ-angular distributions of reaction to determine the σ E2 σ E1 ratio with high accuracy.

Analyzing power of the reaction pp→ppπ0 at a beam energy of 390 MeV

Abstract The analyzing power of the reaction p p→ppπ 0 has been measured at a beam energy of 390 MeV. The dependences of the analyzing power on the pion emission-angle and the relative momentum of two outgoing protons have been obtained. The angular dependence could be decomposed by Legendre polynomial and the relative contribution of the P 21 to the P 11 function is less than 4%. The momentum dependence of the analyzing power has been studied to obtain information about the pion-production mechanism. It has been deduced that pion production due to the long-range interaction plays an important role in the momentum dependence of the P -state amplitude.

84Kr(n,γ)85Kr reaction cross section measured by an NaI(T1) spectrometer between 10 and 80 keV

Abstract A discrete γ-ray emitted promptly from the 84 Kr(n,γ) 85 Kr reaction in the keV energy region has been detected for the first time and thereby the reaction cross section has been accurately determined. The obtained cross section is consistent with the previously accepted data.

Measurement of analyzing power for pp→ppπ0 reaction at 392 MeV

The angular dependence of analyzing power for pp→ppπ0 reaction was measured at 392 MeV using a polarized proton beam and liquid hydrogen target. It is demonstrated that meson exchange model fails to reproduce observed behavior of the analyzing power.