T. Kawabata

The Giant Monopole Resonance in the Sn Isotopes: Why is Tin so "Fluffy"?

The isoscalar giant monopole resonance (GMR) has been investigated in a series of Sn isotopes (A=112-124) using inelastic scattering of 400-MeV a particles at extremely forward angles (including 0 degrees). The primary aim of the investigation has been to explore the role of the symmetry-energy term in the expression for nuclear incompressibility. It is found that the excitation energies of the GMR in the Sn isotopes are significantly lower than those expected from the nuclear incompressibility previously extracted from the available data on the compressional-mode giant resonances.

Precision measurement of vector and tensor analyzing powers in elastic deuteron-proton scattering

Abstract.High-precision vector and tensor analyzing powers of elastic deuteron-proton ( d + p) scattering have been measured at intermediate energies to investigate effects of three-nucleon forces. Angular distributions in the range of 70°-120° in the center-of mass frame for incident-deuteron energies Edlab = 130 and 180 MeV were obtained using the RIKEN facility. The beam polarization was unambiguously determined by measuring the ^12C (d, α)^10B(2+) reaction at 0°. Results of the measurements are compared with state-of-the-art three-nucleon calculations. The present modeling of nucleon-nucleon forces and its extension to the three-nucleon system is not sufficient to describe the high-precision data consistently and requires, therefore, further investigation.

2α+t cluster structure in 11B

Abstract The cluster structures of the excited states in 11B are studied by analyzing the isoscalar monopole and quadrupole strengths in the B 11 ( d , d ′ ) reaction at E d = 200 MeV . The excitation strengths are compared with the predictions by the shell-model and antisymmetrized molecular-dynamics (AMD) calculations. The large monopole strength for the 3 / 2 3 − state at E x = 8.56 MeV is well described by the AMD calculation and is suggested to be an evidence for a well developed 2 α + t cluster structure.

The (t,He-3) and (He-3, t) reactions as probes of Gamow-Teller strength

It is shown via a study on a {sup 26}Mg target that the (t,{sup 3}He) reaction at 115 MeV/nucleon reaction is an accurate probe for extracting Gamow-Teller transition strengths. To do so, the data are complemented by results from the {sup 26}Mg({sup 3}He, t) reaction at 140 MeV/nucleon that allows for a comparison of T=2 analog states excited via the mirror reactions. Extracted Gamow-Teller strengths from {sup 26}Mg(t,{sup 3}He) and {sup 26}Mg({sup 3}He, t) are compared with those from {sup 26}Mg(d,{sup 2}He) and {sup 26}Mg(p,n) studies, respectively. A good correspondence is found, indicating probe independence of the strength extraction. Furthermore, we test shell-model calculations using the new USD-05B interaction in the sd-model space and show that it reproduces the experimental Gamow-Teller strength distributions well. In anticipation of further (t,{sup 3}He) experiments on medium-heavy nuclei aimed at determining weak-interaction rates of relevance for stellar evolution, a second goal of this work is to improve the understanding of the (t,{sup 3}He) and ({sup 3}He, t) reaction mechanisms at intermediate energies because detailed studies are scarce. The distorted-wave Born approximation is employed, taking into account the composite structures of the {sup 3}He and triton particles. The reaction model provides the means to explainmorexa0» systematic uncertainties at the 10%-20% level in the extraction of Gamow-Teller strengths as being because of interference between Gamow-Teller {delta}L=0,{delta}S=1 and {delta}L=2,{delta}S=1 amplitudes that both contribute to transitions from 0{sup +} to 1{sup +} states.«xa0less

Performance of the neutron polarimeter NPOL3 for high resolution measurements

Abstract We describe the neutron polarimeter NPOL3 for the measurement of polarization transfer observables D ij with a typical high resolution of ∼ 300xa0keV at T n ≃ 200 MeV . The NPOL3 system consists of three planes of neutron detectors. The first two planes for neutron polarization analysis are made of 20 sets of one-dimensional position-sensitive plastic scintillation counters with a size of 100xa0cm × 10xa0cm × 5xa0cm, and they cover the area of 100 × 100 cm 2 . The last plane for detecting doubly scattered neutrons or recoiled protons is made of the two-dimensional position-sensitive liquid scintillation counter with a size of 100 cm × 100 cm × 10 cm . The effective analyzing powers A y ; eff and double scattering efficiencies e D . S . were measured by using the three kinds of polarized neutrons from the 2 H ( p ⇒ , n ⇒ ) pp , 6 Li ( p ⇒ , n ⇒ ) 6 Be ( g . s . ) , and 12 C ( p ⇒ , n ⇒ ) 12 N ( g . s . ) reactions at T p = 198 MeV . The performance of NPOL3 defined as e D . S . ( A y ; eff ) 2 are similar to that of the Indiana Neutron POLarimeter by taking into account for the counter configuration difference between these two neutron polarimeters.

Measurement of the Gamow-Teller strength distribution in Co-58 via the Ni-58(t,He-3) reaction at 115 MeV/nucleon

Electron capture and beta decay play important roles in the evolution of presupernovae stars and their eventual core collapse. These rates are normally predicted through shell-model calculations. Experimentally determined strength distributions from charge-exchange reactions are needed to test modern shell-model calculations. We report on the measurement of the Gamow-Teller strength distribution in Co-58 from the Ni-58(t,He-3) reaction with a secondary triton beam of an intensity of similar to 10(6) pps at 115 MeV/nucleon and a resolution of similar to 250 keV. Previous measurements with the Ni-58(n,p) and the Ni-58(d,He-2) reactions were inconsistent with each other. Our results support the latter. We also compare the results to predictions of large-scale shell-model calculations using the KB3G and GXPF1 interactions and investigate the impact of differences between the various experiments and theories in terms of the weak rates in the stellar environment. Finally, the systematic uncertainties in the normalization of the strength distribution extracted from Ni-58(He-3, t) are described and turn out to be nonnegligible due to large interferences between the Delta L=0,Delta S=1 Gamow-Teller amplitude and the Delta L=2,Delta S=1 amplitude.

Charge-changing cross-section measurements of

We have measured for the first time the charge-changing cross sections (

^{12-16}

sigma_{text{CC}}

C at around

) of

45A

^{12-16}