Speaker
Dr
Tomohiro Uesaka
(RIKEN Nishina Center)
Description
A level splitting between a spin doublet, spin-orbit splitting, can be a good measure of spin- orbit coupling in nuclei. Ando-Bando and Pieper-Pandharipande investigated microscopic origins of the 1p spin-orbit splitting in ^{16}O and showed that about half of the splitting originates from the NN spin-orbit interaction and the remaining part from the NN tensor and three- nucleon interactions. According to recent works by Otsuka et al., the tensor force is responsible for the change of proton (neutron) spin-orbit splitting depending on the neutron (proton) number.
We are planning to perform (p(pol), 2p) knockout experiments at RIBF to determine the proton spin-orbit splitting in unstable oxygen isotopes, ^{14,22−24}O. At RIBF energies, quasi-free knockout (p, pN ) reactions can be a good spectroscopic tool to study single hole states. Experiments with spin polarized proton target make it possible to determine spin-parity of the single-hole state with less ambiguity. Thus the experiment will clearly exhibit how the proton spin-orbit split- ting changes from the values of about 6 MeV for ^{16}O when neutrons are added (removed) to d5/2 s1/2 and s1/2 orbits (from a p1/2 orbit). This neutron-number dependence of the spin-orbit splitting is expected to provide a unique opportunity to pin down the relevance of tensor and three-body interactions to nuclear structure clearly.
Prior to the RIBF experiment, we have carried out a ^{18}O(p(pol),2p) experiment at the ring cyclotron facility of RCNP, Osaka University and found that the proton spin-orbit splitting in ^{18}O is smaller by about 0.5 MeV than that in ^{16}O.
In the symposium, results from the ^{18}O(p(pol),2p) experiment at RCNP and the future plan of the ^{14,22−24}O(p(pol),2p) experiment at RIBF will be discussed.
Primary author
Dr
Tomohiro Uesaka
(RIKEN Nishina Center)
Co-author
Mr
Shoichiro Kawase
(Center for Nuclear Study, University of Tokyo)
