Seminar Details

Recent Controversial Results Regarding the Hoyle State Decay

Christopher Prokop, NSCL
Thursday, December 13, 11:00 AM - Research Discussion
NSCL Lecture Hall

During the helium burning phase of stellar nucleosynthesis, the production of 12C proceeds via a two-step process called the triple alpha reaction. In this reaction, two alpha particles react to form 8Be which is followed by the capture of a third alpha particle onto 8Be forming 12C. The second step of this reaction is enhanced by a narrow resonance with a 7.65 MeV 0+ state in 12C, the Hoyle state. The production rate of 12C is sensitive to the properties of the Hoyle state [1-4]. The work of Ref. [1] suggested the decay of Hoyle state proceeds almost exclusively through a sequential 8Beg.s. + α channel and placed an upper limit of 4% on the contribution of the direct decay to three alpha particles [1]. Recent controversial results of the decay properties of the Hoyle state identify two new exotic direct three alpha decay modes with a combined decay branch of 17%, which implies a decrease of 17% in the production rate of 12C at temperatures of 108 to 109 K [2]. Subsequent studies attempting to resolve the apparent discrepancy between the previous investigations support the findings of Ref. [1] and find little evidence of the two newly proposed direct three alpha decay modes [3,4]. The experimental details and results will be presented along with conclusions regarding the Hoyle state decay controversy.

References:
1. M. Freer et al., Phys. Rev. C 49 R1751 (1994)
2. A. R. Raduta et al., Phys. Lett. B 65 705 (2011)
3. O. S. Kirsebom et al., Phys. Rev. 108 202501 (2012)
4. J. Manfredi et al., Phys Rev. C 85 037603 (2012)