论文标题
hoyle状态的直接3 $α$衰减的严格上限为$^{12} $ c
A stringent upper limit on the direct 3$α$ decay of the Hoyle State in $^{12}$C
论文作者
论文摘要
我们研究了第二个$ j^π= 2^+$状态的最新观察结果的含义，该$^{12} $ c是使用$^{12} $ c（$γ$，$α$）$^8 $ be $ _ {\ textrm {\ textrm {（G.S。）} $反应进行测量的。除了将$^{12} $ C分解为$α$ - 零件和$^8 $处于其基础状态外，一小部分事件（2％）被确定为$^8 $ be中激发态的直接衰减和衰减。这允许对直接3 $α$部分衰减宽度的限制确定为$γ_{3α} <32（4）$ kev。由于所有理论模型都预测了这个2 $^+$状态是对霍伊尔州的集体激发，因此，霍伊尔州的3 $α$部分宽度可以从霍伊尔的3 $α$衰减渗透率的比率和2 $^+$ state中计算出来。这是使用半古典WKB方法计算得出的，我们推断出$ {γ__{3α} \ yoctim ofγ} <5.7 \ times 10^{ - 6} $的Hoyle状态的直接衰减分支比的严格上限。该结果将这种罕见衰减模式的直接测量超出了当前的实验能力。
We investigate an implication of the most recent observation of a second $J^π= 2^+$ state in $^{12}$C, which was measured using the $^{12}$C($γ$,$α$)$^8$Be$_{\textrm{(g.s.)}}$ reaction. In addition to the dissociation of $^{12}$C to an $α$-particle and $^8$Be in its ground state, a small fraction of events (2%) were identified as direct decays and decays to excited states in $^8$Be. This allowed a limit on the direct 3$α$ partial decay width to be determined as $Γ_{3α} < 32(4)$ keV. Since this 2$^+$ state is predicted by all theoretical models to be a collective excitation of the Hoyle state, the 3$α$ partial width of the Hoyle state is calculable from the ratio of 3$α$ decay penetrabilities of the Hoyle and 2$^+$ states. This was calculated using the semi-classical WKB approach and we deduce a stringent upper limit for the direct decay branching ratio of the Hoyle state of ${Γ_{3α} \over Γ} < 5.7 \times 10^{-6}$, over an order of magnitude lower than previously reported. This result places the direct measurement of this rare decay mode beyond current experimental capabilities.
