Anthropic Importance of the “Bretscher State” in DT Fusion

Abstract

The term “Bretscher state” may not be as familiar as “Hoyle state,” but its anthropic importance cannot be overstated. In Big Bang nucleosynthesis, the deuterium-tritium (DT) fusion reaction 3H ( d , n ) 4 He, enhanced by the 3/2+ resonance due to the Bretscher state, is responsible for ∼ 99 % of primordial 4He. While this fact has been known for decades, it has not been widely appreciated, and we recently proposed that its significance be commemorated by naming the 3/2+ state after Egon Bretscher, its discoverer. The importance of the resonant nature of the DT fusion reaction has been amplified by recent activities related to the production and use of terrestrial fusion including recent, net gain shots at the National Ignition Facility. Here, we aim to highlight the anthropic importance of the 4He-producing DT reaction that plays such a prominent role in models of nucleosynthetic processes occurring in the early universe. This primordial helium serves as a source for the subsequent creation of ≥ 25 % of the carbon, 12C and other heavier elements that comprise a substantial fraction of the human body. Further studies are required to determine a better characterization of the amount of 12C than this lower limit of 25%. Some scenarios of core stellar nucleosynthetic yield of 12C suggest that even higher percentages of carbon from primordial helium are possible.