Radiative decay branching ratio of the Hoyle state

In 1954 Fred Hoyle postulated that a 7.65 MeV excited state in ¹²C had to exist for carbon-based life to develop on Earth. During stellar helium burning, such a state allows a short-lived ⁸Be, formed from two α particles, to resonantly react with a third α particle to form this state which can decay to the ¹²C ground state via γ or electron-positron pair emission. The branching fraction for this radiative decay determines the amount of ¹²C produced in stars. A recent experiment suggested that the decay was significantly different from previous results from the 1960's and 1970's, adding considerable uncertainty to this important reaction. This paper uses modern detection technology to remeasure the branching ratio with reduced uncertainties compared with the new result and confirms that the earlier results were correct, thus significantly reducing the uncertainty in stellar ¹²C production.