Search

The effects of three nucleon force (3NF) have been actively studied via the nucleon–deuteron (Nd) scattering states. The differential cross sections and the vector analyzing powers A y of the 2H(p, n) inclusive breakup reaction at 170 MeV were measured for the study of 3NF effects in the intermediate energy region. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD2) target and the energy of scattered neutrons were measured by using TOF method. The data were compared with the Faddeev calculations based on modern nucleon–nucleon (NN) forces with and without the 3NF. Concerning the differential cross sections, we can see large discrepancies between the data and the calculations in the region of scattered neutron energies are low, which is similar to the results of the 2H(p, p) inclusive breakup reaction at 250 MeV.

The triple α reaction rate in stars is quite important in many astrophysical scenarios including the stellar evolution and carbon synthesis in stars. Recently the non-resonant triple α reaction rate has been reevaluated using a calculation with the continuum-discretized coupled-channels (CDCC) method, which dramatically increased the rate at low temperature compared to the widely-used NACRE compilation. Since the enhancement influences strongly on astrophysical model simulations, we have planned an experiment for drawing conclusion on the non-resonant triple α reaction rate at low temperature by measuring the three-α continuum state in 12C. We report the present situation of the experiment.

Tensor correlations in 4He were studied via the (p, dp) reaction at the incident energy of 392 MeV with a focus on spin configurations of correlated pn pairs in 4He at high relative momenta \({(P_{\rm rel}^{\rm cor})}\). The preliminary results show that the correlated pn pair at \({P_{\rm rel}^{\rm cor} = 310 {\rm MeV/c}}\) predominantly has the channel spin S = 1, which is consistent with the characteristics of tensor correlations.

Spectroscopy for neutron-rich nuclei 9He and 12Be has been performed by means of heavy-ion double charge exchange (HIDCX) (18O, 18Ne) reaction on stable target nuclei 9Be and 12C, respectively. Several clear peaks in 12Be at low excitation energy region even above neutron separation energy have been observed in one-shot measurement, whereas no prominent signals of 9He have been observed owing to the small cross section. It is shown that the HIDCX reaction is a new powerful spectroscopic tool for study of unstable neutron-rich nuclei.

For the study of three nucleon force (3NF) effects in the intermediate energy region, the differential cross sections and the vector analyzing power Ay were measured for the 2H(p, n) inclusive breakup reaction at 170 MeV. The polarized proton beam of 170 MeV was injected to the deuterated polyethylene (CD2) target and the energy of scattered neutrons were deduce by TOF method. The data was compared with the results of the Faddeev calculations with and without 3NFs. Concerning about the differential cross sections, we can see large discrepancies between the data and the calculations in the region where the energies of scattered neutrons are low, which are similar to the results of the 2H(p, p) inclusive breakup reaction at 250 MeV.

Cross sections of pd breakup reaction at E p = 250 MeV were measured systematically in single-proton detection and in two-proton coincidence detection. Measured cross section is up to two times higher than calculated ones. The enhancement of breakup cross section is similar to reported enhancement in pd elastic scattering cross section. Origins of this enhancement are discussed.

The alpha inelastic scattering from 24Mg was measured to obtain the isoscalar natural-parity excitation strengths and to search for the α-condensed states. The multipole decomposition analysis for the measured cross sections was performed. The strength distributions for the \({{\Delta}L=0{-}3}\) were successfully obtained and the possible candidates for the α-condensed states around the 16O core were found.

The effects of three-nucleon force (3NF) has been actively studied by using the nucleon–deuteron (Nd) scattering states. The differential cross sections of the elastic Nd scattering at the energy below 150 MeV can be well reproduced by incorporating 3NF in the Faddeev calculation based on modern nucleon–nucleon (NN) interactions. On the other hand, the differential cross sections of Nd elastic and inelastic scatterings at 250 MeV show large discrepancies between the data and the Faddeev calculations with 3NF. It indicates the presence of the missing features of the three nucleon system at this energy region. For the systematic study about the energy dependence of this large discrepancies, we measured the differential cross sections and the vector analyzing power A y for the 2H(p, n) inclusive breakup reaction at 170 MeV. The experiment was carried out at RCNP by detecting scattered neutrons by using the neutron detector NPOL3. The data was compared with the results of the Faddeev calculations with and without the 3NF.

Inclusive measurements of the D(p, p)pn reaction were made at incident proton energies of 248 MeV and 13 MeV, to investigate the global feature of the pd breakup reaction at intermediate and low energies. At 248 MeV, the cross section and analyzing power A y were measured at four angles from 7° to 20°. The data largely disagree with Faddeev calculations even if 2π-exchange three-nucleon force (2π3NF) or Δ-isobar is included, and the disagreement increases at forward angles. At 13 MeV, the cross section was measured at eight angles from 10° to 70°. The data are well reproduced by a recent pd Faddeev calculation, and the effects of Δ-isobar at 13 MeV are very small.

In our previous inclusive experiment on 2H(p, p)pn at 247 MeV, the measured cross section at forward angles is about twice larger than 3N calculation with ππ 3NF. Therefore, we have made an exclusive experiment on 2H(p, p1 p2)n at the same energy. The preliminary data suggest that the cross section was enhanced at forward angle of θ1 and θ2.

In our previous measurement of pd radiative capture at Ed = 137 and 196 MeV, we found an interesting fact that the measured tensor analyzing powers show the relation Axx ≈ Ayy, although calculated Axx and Ayy are apparently different, Axx ≠ Ayy. The measured Ayy agrees fairly well with the 3N calculations, and the measured Axx largely disagrees with calculated Axx. Similar experiments on pd capture have been made at KVI at nearly the same energies of 130–180 MeV. The KVI data also support Axx ≈ Ayy relation, but absolute values of Axx and Ayy at KVI are about half of RCNP data. Therefore, we made a new experiment of pd capture at Ed = 196 MeV. Azz was measured in three different ways, and data analysis is in progress. Preliminary data seem to support our previous data.