T. Taguchi

Development of Neutron Polarization Measurement System for Studying NN interaction in Nuclear Medium

We have developed the neutron polarization measurement system to perform the first polarization-transfer measurement for the exclusive (p,np) reaction. For the neutron polarization measurement, we have reconstructed the neutron polarimeter NPOL3. The NPOL3 system has been calibrated by using the polarized neutron from the 2H(p→,n→) reaction, and the resulting effective analyzing power is Ay:eff = 0.127. For the exclusive measurement, the Large Acceptance Spectrometer (LAS) has been used for the recoil proton detection. The energy resolution of 6 MeV is achieved for separation energy, which is sufficient to separate the 1s and 1p orbits for light nuclei.

Study of Three-Nucleon Force Effect via Few-Nucleon Scattering

A complete set of deuteron analyzing powers for elastic deuteron-proton(dp) scattering at 250 and 294 MeV/nucleon has been measured. The obtained data are compared with the Faddeev calculations based on the modern nucleon-nucleon forces together with three-nucleon forces.

Complete Set of Deuteron Analyzing Powers for dp Elastic Scattering at Intermediate Energies and Three Nucleon Forces

Few-nucleon scattering at intermediate energies (E/A ∼ 200 MeV) is one attractive approach to investigate the dynamical aspects of 3NFs, such as momentum and/or spin dependences. Direct comparison between the data and the rigorous numerical calculations based on bare nuclear potentials provides information of 3NFs. So far large 3NF effects are theoretically predicted and experimentally confirmed in the cross section minimum for dp scattering at ∼ 100 MeV/nucleon. With the aim of clarifying roles of the 3NFs in nuclei the experimental programs with polarized deuterons beams at intermediate energies are in progress at RIKEN RI Beam Factory (RIBF) [1]. We have measured all deuteron analyzing powers (iT11, T20, T21, and T22) for deuteron–proton (dp) elastic scattering at 70–300 MeV/nucleon, typically in step of 50 MeV/nucleon. The vector and tensor polarized deuteron beams were accelerated by three cyclotrons, AVF, RRC and SRC. The measurement of deuteron analyzing powers for elastic dp scattering was carried out using the polarimeter BigDpol installed at the extraction beam line of the SRC. The deuteron beams bombarded a polyethylene (CH2) target in the scattering chamber. Scattered deuterons and recoil protons were detected by plastic scintillators in kinematical coincidence conditions. The obtained high precision data are compared with the results of three-nucleon Faddeev calculations based on the nucleon-nucleon (NN) potentials; i.e. CD Bonn, Argonne V18, Nijmegen I, and II, alone or combined with the Tucson-Melbourne’99 and the Urbana IX 3NFs. Large discrepancies between the pure NN theory and the data, which are not resolved even by adding the current 3NFs, are found at the c.m. backward angles for almost all the deuteron analyzing powers with increasing an incident energy. In the conference the comparison between the data and the calculations based on the χ EFT potentials [2] will also be presented.

Complete set of deuteron analyzing powers for dp elastic scattering at intermediate energies

With the aim of clarifying roles of the 3NFs in nuclei experimental programs with polarized deuterons beams at intermediate energies are in progress at RIKEN RI Beam Factory. As the first step, we have measured a complete set of deuteron analyzing powers (iT11, T20, T21, T22) in deuteron-proton elastic scattering at 250 and 294 MeV/nucleon. The obtained data are compared with the Faddeev calculations based on the modern nucleon-nucleon forces together with the Tucson-Melbourne’99, and UrbanaIX three nucleon forces.