Y. Satou

Identification of 45 New Neutron-Rich Isotopes Produced by In-Flight Fission of a 238U Beam at 345 MeV/nucleon

A search for new isotopes using in-flight fission of a 345 MeV/nucleon 238 U beam has been carried out at the RI Beam Factory at the RIKEN Nishina Center. Fission fragments were analyzed and identi...

Analyzing power in elastic scattering of 6He from a polarized proton target at 71 MeV/nucleon

The vector analyzing power has been measured for the elastic scattering of neutron-rich {sup 6}He from polarized protons at 71 MeV/nucleon making use of a newly constructed solid polarized proton target operated in a low magnetic field and at high temperature. Two approaches based on local one-body potentials were applied to investigate the spin-orbit interaction between a proton and a {sup 6}He nucleus. An optical model analysis revealed that the spin-orbit potential for {sup 6}He is characterized by a shallow and long-ranged shape compared with the global systematics of stable nuclei. A semimicroscopic analysis with an {alpha}+n+n cluster folding model suggests that the interaction between a proton and the {alpha} core is essentially important in describing the p+{sup 6}He elastic scattering. The data are also compared with fully microscopic analyses using nonlocal optical potentials based on nucleon-nucleon g matrices.

Unbound excited states in 19,17C

The neutron-rich carbon isotopes 19,17C have been investigated via proton inelastic scattering on a liquid hydrogen target at 70 MeV/nucleon. The invariant mass method in inverse kinematics was employed to reconstruct the energy spectrum, in which fast neutrons and charged fragments were detected in coincidence using a neutron hodoscope and a dipole magnet system. A peak has been observed with an excitation energy of 1.46(10) MeV in C, while three peaks with energies of 2.20(3), 3.05(3), and 6.13(9) MeV have been observed in C. Deduced cross sections are compared with microscopic DWBA calculations based on p-sd shell model wave functions and modern nucleon-nucleus optical potentials. Jπ assignments are made for the four observed states as well as the ground states of both nuclei.

Analyzing power for proton elastic scattering from the neutron-rich He6 nucleus

Vector analyzing power for the proton-{sup 6}He elastic scattering at 71 MeV/nucleon has been measured for the first time, with a newly developed polarized proton solid target, which works at a low magnetic field of 0.09 T. The results are found to be incompatible with a t-matrix folding model prediction. Comparisons of the data with g-matrix folding analyses clearly show that the vector analyzing power is sensitive to the nuclear structure model used in the reaction analysis. The {alpha}-core distribution in {sup 6}He is suggested to be a possible key for understanding the nuclear structure sensitivity.

Measurement of the tensor analyzing power T20 in the dd→He3n and dd→H3p at intermediate energies and at zero degree

The data on the tensor analyzing power T20 in the dd->^3Hen and dd->^3Hp reactions at 140, 200 and 270 MeV of the deuteron kinetic energy and at zero degree obtained at RIKEN Accelerator Research Facility are presented. The observed positive sign of T20 clearly demonstrates the sensitivity to the D/S wave ratios in the ^3He and ^3H in the energy domain of the measurements. The T20 data for the ^3He-n and ^3H-p channels are in agreement within experimental accuracy.

Search for low lying dipole strength in the neutron rich nucleus 26Ne

Coulomb excitation of the exotic neutron-rich nucleus 26Ne on a natPb target was measured at 58 A.MeV in order to search for low-lying E1 strength above the neutron emission threshold. Data were also taken on an natAl target to estimate the nuclear contribution. The radioactive beam was produced by fragmentation of a 95 A.MeV 40Ar beam delivered by the RIKEN Research Facility. The set-up included a NaI gamma-ray array, a charged fragment hodoscope and a neutron wall. Using the invariant mass method in the 25Ne+n channel, we observe a sizable amount of E1 strength between 6 and 10 MeV. The reconstructed 26Ne angular distribution confirms its E1 nature. A reduced dipole transition probability of B ( E 1 ) = 0.49 ± 0.16 e2fm2 is deduced. For the first time, the decay pattern of low-lying strength in a neutron-rich nucleus is obtained. The results are discussed in terms of a pygmy resonance centered around 9 MeV.

MEASUREMENT OF p+d ELASTIC SCATTERING AT EP = 392 MEV

The cross sections and spin observables of the p+d elastic scattering have been measured at 392 MeV. The results are compared with the results of Faddeev calculations with and without including the three nucleon force.

Reaction mechanism and characteristics ofT20ind+3Hebackward elastic scattering at intermediate energies

For backward elastic scattering of deuterons by ^3He, cross sections \sigma and tensor analyzing power T_{20} are measured at E_d=140-270 MeV. The data are analyzed by the PWIA and by the general formula which includes virtual excitations of other channels, with the assumption of the proton transfer from ^3He to the deuteron. Using ^3He wave functions calculated by the Faddeev equation, the PWIA describes global features of the experimental data, while the virtual excitation effects are important for quantitative fits to the T_{20} data. Theoretical predictions on T_{20}, K_y^y (polarization transfer coefficient) and C_{yy} (spin correlation coefficient) are provided up to GeV energies.

Total Spin Transfer in Continuum for 90Zr(p,n) Reaction at 295 MeV

A complete set of polarization transfer observables has been measured for the 90 Zr( p , n ) reaction at T p = 295 MeV and θ lab = 0°. The measurement can yield the total spin transfer Σ(0°) which is independent of nuclear reaction mechanisms such as the effective nucleon–nucleon interaction or distortions. The deduced Σ(0°) values indicate the strong spin-flip characteristics of the continuum up to 50 MeV excitation. A predominance of unnatural-parity transitions in the continuum is also observed from polarization transfer observables.

THE ANGULAR DISTRIBUTIONS OF THE VECTOR Ay AND TENSOR Ayy, Axx, Axz ANALYZING POWERS IN THE dd → 3Hp AND dd → 3Hen REACTIONS AT Ed = 200 AND 270 MeV

The data on the vector Ay and tensor Ayy, Axx, Axz analyzing powers for the and reactions at Ed = 200 and 270 MeV are presented. The data demonstrate large values of analyzing powers and their strong variation versus the scattering angle. The observed negative sign of the tensor analyzing powers for these reactions at small angles clearly demonstrate the sensitivity to the D/S ratio of the 3H and 3He wave functions, respectively. The calculations performed within one-nucleon exchange model with the use of the standard three-nucleon bound state wave functions fail to reproduce the data on the tensor analyzing powers.