Toy model for the Hoyle decay of 12C

The Hoyle decay of 12C is the opposite effect of the important triple-alpha process in the hotter stars. Researchers at IFA are studying one in other to better understand the other.

2018.04.09 | Ole J. Knudsen

The Triple-alpha-proces. Astrophysicists, please read from left to right. Physicists from right to left, thank you!

In stars hotter than our Sun some of the energy production occurs as the 'triple-alpha-process' whereby 3 alpha particles fusion, most often sequentially via an intermediate state of 8Be, ending up as a 12C nucleus. Knowledge of this process, and especially how often it bypasses the intermediate state is critical for understanding the state and development of these stars. By 'thinking backwards' physicists can help by studying the decay of an exited 12C nucleus - in the socalled Hoyle state -

 12C(Hoyle) -> 8Be + alfa; 8Be->alfa+alfa

Phase space distribution for direct decay from the Hoyle stade according to model 1

In Physics Letters B 10 April 2018 IFA researchers J. Refsgaard, H. O. U. Fynbo, O. S. Kirsebom and K. Riisager, study what they call a toy model for both the sequential and the rarer direct decay. They are using a well tested phenomenological model to predict the decay, a.o. how the electromagnetic repulsion from the three charged particles influence on the process.

The paper, titeled 'Three-body effects in the Hoyle-state decay' shows what deviations are to be expected from the naive sequential idea in one out of some 1000 decay events. This is close to the presently obtainable experimental sensitivity, making it so much more desirable to try to actually measure these effects. And there are plans for doing this at a later time.

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