Abstract
The existence of the and states around 10 MeV excitation energy in is confirmed by a fully microscopic cluster model. Firstly, a generator coordinate method (GCM) calculation is performed by superposing optimized Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave functions with the radius-constraint method. The obtained two excited states above the Hoyle state are consistent with the recently observed states by experiment. Secondly, a variational calculation using the single THSR wave function orthogonalized to the ground and Hoyle states is made and it also supports the existence of the state obtained by the GCM calculation. The analysis of the obtained state is made by studying its reduced width amplitude, its correlation function, and the large monopole matrix element between this state and the Hoyle state, which shows that this state is a breathing-like excited state of the Hoyle state. This character of the state is very different from the state which seems to have a bent-arm structure.
- Received 7 July 2016
DOI:https://doi.org/10.1103/PhysRevC.94.044319
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