The radiative decay of the Hoyle state serves as the gateway to the production of heavier elements in a stellar environment. Here, we present an exclusive measurement of electric quadruple (E2) transitions of the Hoyle state to the ground state of 12C through the 12C(p, p′γγ)12C reaction. A triple coincidence measurement yields the radiative branching ratio Γrad/Γ = 4.01 (30) × 10−4. This result was corroborated by an independent experiment based on the complete kinematical measurement via12C(p, p′)12C reaction, yielding a consistent result of Γrad/Γ = 4.04 (30) × 10−4. Combining our results with the currently adopted values of Γπ(E0)/Γ and Γπ(E0), the radiative width of the Hoyle state is determined to be 3.75 (40) × 10−3 eV. It is important to note that our finding do not align with a recently reported 34% increase in the radiative decay width of the Hoyle state but is consistent with the currently accepted value.

中文翻译：

---

Hoyle 状态辐射过渡宽度的新测量


霍伊尔态的辐射衰变是在恒星环境中产生较重元素的门户。在这里，我们提出了通过 12C（p， p′γγ）12C 反应从 Hoyle 态到 12C 基态的电四元 （E2） 跃迁的独家测量。三重合测量得出辐射分支比 Γrad/Γ = 4.01 （30） × 10−4。这一结果得到了一项独立实验的证实，该实验基于通过 12C（p， p′）12C 反应的完整运动学测量，产生了 Γrad/Γ = 4.04 （30） × 10−4 的一致结果。将我们的结果与当前采用的 Γπ（E0）/Γ 和 Γπ（E0） 值相结合，霍伊尔态的辐射宽度确定为 3.75 （40） × 10−3 eV。需要注意的是，我们的发现与最近报道的霍伊尔态辐射衰变宽度增加 34% 不一致，但与目前接受的值一致。