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HK: Fachverband Hadronen und Kerne
HK 42: Few-body physics
HK 42.4: Talk
Tuesday, March 17, 2009, 17:30–17:45, H-ZO 100
The role of general symmetries in the three-alpha decay of 12C resonances — •Oliver Kirsebom — Institut for Fysik og Astronomi, Aarhus Universitet, 8000 Århus C, Denmark
We use the Dalitz plot to study the decay of 12C resonances into three alpha particles. The requirement of a symmetric three-alpha final state together with conservation of spin, parity and isospin forces the density to vanish in certain regions of the Dalitz plot thereby inducing general structures that do not in any way depend on the details of the interaction Hamiltonian except, of course, its ability to conserve spin, parity and isospin. The implications of this understanding is twofold. First, the observed density of the Dalitz plot can be used to determine or at least impose constraints on the spin and parity of the decaying 12C resonance. Second, once the inevitable structures due to symmetries have been identified the remaining structures in the Dalitz plot can be understood as resulting from the dynamical interactions at play, thus allowing for an understanding of the decay mechanism. In this contribution I present experimental Dalitz plots extracted from complete kinematics studies of the 10B(3He,pααα) and the 11B(3He,dααα) reactions. I show how our measurements allow us to determine the spin and parity of 12C states whose quantum numbers were hitherto unknown. Finally, I compare the measured Dalitz distributions to theoretical calculations and discuss the implications for our understanding of the decay mechanism, in particular the validity of the model of a sequential decay through the broad 2+ resonance in 8Be.