R. Matsumiya

An EDM measurement with a new comagnetometer and a high density UCN source

We discuss a new neutron EDM measurement of 10−28 e cm. For the improved UCN density, we will apply a new spallation UCN source of superfluid He. For magnetometry, 129Xe nuclear spins are injected into a EDM cell, to supress GPE. Performance of the prototype KEK-RCNP UCN source, and the obtained Ramsey resonance spectra are presented.

Precise Studies of Nucleon Density Distribution of 6He and 8He

Reaction cross sections (σR) for 6He and 8He have been measured on 9Be, 12C, and 27Al targets at intermediate energies. We deduced the nucleon density distribution of 6He and 8He through our data with the use of modified Glauber calculation. This method is a sensitive probe for dilute nucleon density and we successfully clarified the halo structure of 6He and the neutron skin‐type density distribution of 8He.

New Study of Reaction Cross Sections and the Nucleon Density Distribution

Reaction cross sections (σR) for 12C beam on 9Be, 12C, and 27Al targets and for 11Be beam on 9Be target were precisely measured systematically in the intermediate energy range. It is indicated that these all σR data were successfully reproduced by a modified Glauber calculation, which is expected to be applied for the determination of density distributions of other exotic nuclei.

Measurement of nEDM with a He-II Spallation UCN Source

A neutron EDM measurement by means of a He-II spallation UCN source is discussed. For an improvement in the statistical error, a proton beam power is increased up to 20 kW so that a UCN density in an EDM measurement cell becomes 800 UCN/cm. The  heating in a He-II bottle is removed by using a He cryostat. Polarized UCN are extracted from the He-II bottle through an aluminum window by using a superconducting magnet for Ramsey resonance in the EDM cell. For an improvement in the systematic error, Xe nuclear spins are used for magnetic field monitoring in the EDM cell. A geometric phase effect is suppressed by a buffer gas effect.

Reaction cross section studies at NIRS and RIBF

Reaction cross sections for stable nuclei at intermediate energies have been measured precisely and systematically. The data have been found to be reproduced nicely by the optical‐limit approximation of Glauber theory modified to include the nucleon multiple scattering effect and the Fermi‐motion effect. Applying this prescription, the nucleon density distribution of 17Ne has been studied. The surface structure of 8B and 11Be has been also studied using this prescription and hydrogen targets. Using the RIBF that has just started application to studies of exotic nuclei, neutron‐rich Ne isotopes around the Island of Inversion have been investigated through measurements of their interaction cross sections.

Decay curve study in a standard electron capture decay

We have searched for a time‐modulated decay in a standard electron capture experiment for 140Pr, in order to confirm a report from GSI, where an oscillatory decay has been observed for hydrogen‐like 140Pr and 142Pm ions in the cooler storage ring. 140Pr has been produced with the 140Ce(p, n) reaction by a pulsed proton beam accelerated from the Van de Graaff accelerator at Osaka University. Resultant time dependence of the Kα and Kβ X‐ray intensities from the daughter shows no oscillatory behavior.

Electromagnetic Moments of Proton-Rich {sup 28}P and Decomposition of Its Spin

The magnetic moment of 28P(Iπ = 3+, T1/2 = 270.3 ms) has been measured precisely by means of β‐NMR technique. The obtained magnetic moment is |μ(28P)| = 0.3115 (34) μN. Combined with the magnetic moment of its mirror partner 28Al, the nuclear spin I = 3 is decomposed into its 4 components. The measurement of the Q moment has also been tried. From the preliminary NQR spectrum, it was found that the quadrupole coupling constant eqQ/h may be slightly larger than the prediction, which may show enhancement of the Q moment.

Polarization and momentum distribution of 23Ne and 25Al produced in one nucleon pickup reactions at 10A MeV

We measured the polarization of the β‐emitting 23Ne (Iπ = 5/2+, T1/2 = 37.24 s) and 25Al(Iπ = 5/2+, T1/2 = 7.18 s), produced through the one nucleon pickup reactions in the intermediate energy heavy ion collisions, and was compared with those from the projectile fragmentation process. The larger polarization which seems to persistently be positive throughout the momentum distribution, and sharper momentum distributions suggest nuclear friction mechanism to be responsible for the polarization phenomena. Using such a large polarization, magnetic moment of 23Ne and the quadrupole moment of 25Al were measured. The obtained values are |μ(23Ne)| = 1.0817(9) μN and |Q(25Al)| = (240 ± 20) mb.

Alignment Correlation Terms In β‐Ray Angular Distributions From Spin Aligned 20F And 20Na

The β‐ray angular distribution from the purely aligned nuclei, 20F(Iπ = 2+, T1/2 = 11.00s) and 20Na(Iπ = 2+, T1/2 = 447.9ms), have been measured to test the G symmetry in the weak nuclear currents. The alignment terms α∓ of mirror pair in the mass number A = 20 system have been obtained as a function of β‐ray energy with the preliminary analysis.

Measurement of the spin and magnetic moment of {sup 23}Al

For the first time, we obtained the g factor for the ground state of {sup 23}Al by use of a {beta}-NMR measurement. {sup 23}Al has a small proton separation energy and is a potential proton-halo candidate. The obtained g factor, vertical bar g vertical bar =1.557{+-}0.088, clearly shows the spin and parity, J{sup {pi}}=5/2{sup +}, for {sup 23}Al, which is the same as that of its mirror partner, {sup 23}Ne. The possible nuclear structure of {sup 23}Al is also discussed.