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Structure and rotations of the Hoyle state
Evgeny Epelbaum1, Hermann Krebs, Timo A Lähde
1Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44870 Bochum, Germany.
Physical Review Letters
|February 2, 2013
Summary
Researchers used ab initio lattice calculations to reveal the structure of the Hoyle state in carbon-12 nuclei. This state is crucial for carbon production in stars, showing a distinct "bent-arm" alpha cluster configuration.
Area of Science:
- Nuclear Physics
- Astro-nuclear Physics
- Computational Physics
Background:
- The Hoyle state in carbon-12 is fundamental for stellar nucleosynthesis, enabling carbon production via triple-alpha fusion in red giant stars.
- Understanding its unique structure is a long-standing challenge in nuclear physics, crucial for astrophysical models.
Purpose of the Study:
- To elucidate the microscopic structure of the Hoyle state and other low-lying states in carbon-12 using advanced computational methods.
- To investigate the alpha cluster configurations and electromagnetic transition rates between these states.
Main Methods:
- Employed ab initio lattice quantum chromodynamics (Lattice QCD) calculations to simulate the carbon-12 nucleus.
- Analyzed the spatial arrangement of alpha clusters within the nucleus for different energy states.
- Computed electromagnetic transition rates to characterize the excited states.
Main Results:
- Identified a compact triangular alpha cluster configuration for the carbon-12 ground state and its first excited spin-2 state.
- Revealed a 'bent-arm' or obtuse triangular alpha cluster configuration for the Hoyle state and its second excited spin-2 state.
- Calculated electromagnetic transition rates between the low-lying states of carbon-12.
Conclusions:
- The study provides unprecedented insight into the structural properties of the Hoyle state, confirming its non-conventional 'bent-arm' alpha cluster arrangement.
- These findings have significant implications for understanding carbon formation in stars and refining astrophysical models.
- The calculations offer a benchmark for future theoretical and experimental investigations of light nuclei.
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