What determines the driplines of atomic nuclei?, by Takaharu Otsuka (CNS + RIBF Seminar #295)

by Prof. Takaharu Otsuka (UT & RIKEN)




This seminar, What determines the driplines of atomic nuclei, is a set of two talks in Japanese and English. The contents are
basically the same.
   Speaker Prof. Takaharu Otsuka (UT and RNC)
                  大塚孝治 名誉教授 (東大、RNC)
   Japanese talk Nov5(Fri) 1030-
   English talk  Nov5(Fri) 2300-

<English> nov5 23:00 JST(+9)
    passcode: 739441

  abstract :
The establishment of the location of driplines and the clarification of related physics are among the most important research missions of RI-beam facilities. The recent measurement on F, Ne and Na isotopes at RIKEN RIBF is a significant achievement in this field.

Within conventional understanding, there are loosely bound neutrons in nuclei at neutron driplines, and these neutrons form neutron halo or skin depending on the situations. This is based upon the picture that single-particle states in the mean potential for neutrons are occupied from the lowest ones.
Our recent theoretical study*, however, suggests that this is not the case for F, Ne or Na isotopes. The correlations between nucleons, such as shape deformation, contribute to the nuclear binding energy. This effect changes from nucleus to nucleus. Such changes are directly related to the driplines, and can be evaluated by ab initio (-type) calculations these days. If this effect increases as a function of the neutron number, the dripline is shifted away. Beside this effect, the monopole effects from the nuclear forces push the dripline away. Once the correlation (or deformation mostly) starts to become weaker beyond the monopole, the dripline emerges. The nucleus then becomes unbound “suddenly” without having loosely bound neutrons.

I will explain this new mechanism as pedagogically as possible. I will touch upon its generality over heavier nuclei and possible experimental verifications.  In particular, I would like to discuss recent issues, for
instance, its relation to proton-density and neutron-density distributions, and to the existence of substantial neutron skin in deformed nuclei, as possible future topics of the physics of unstable nuclei.

* N. Tsunoda et al, Nature, 587, 66 (2020).