Study of nuclear excited states through quantised angular momentum

by Dr Makito Oi (Institute of Natural Sciences, Senshu University)

Friday 22 Jun 2012, 11:00 → 11:40 Europe/Zurich

26-1-022 (CERN)

The study of yrast states, a group of lowest energy states for given angular momentum, has been a primary interest to nuclear structure physics since the 1970s, when “backbending” was discovered as a possible phase transition phenomenon in nuclear finite many-body systems. Nuclear rotation is regarded to have a role analogous to a “magnetic field” in triggering structural changes. Multi-quasiparticle states and rotational alignment were intensively investigated to provide a physical interpretation of the transition. After 2000, more exotic interpretations were proposed in addition to these conventional ideas. The best known case is “nuclear chiral rotation”. As a possible configuration, angular momentum vectors for valence protons, valence neutrons and collective rotation of the core all point in different directions to produce the nuclear chirality. However, the present model for nuclear chirality is based on a static and classical model, where angular momentum is not quantised. It is thus interesting to know whether nuclear chirality can survive quantum fluctuations, which counteract to destabilize the chiral configuration. One can study such exotic nuclear rotations with quantised spin by means of quantum number projection methods. I have recently derived a new formula to help carrying out the relevant calculations using these methods. I would like to explain how helpful the formula is in order to understand excited states at high angular momentum, which is quantised.