标题： dd → 4He η 反应近阈值处 显示英文标题

标题： The dd -> 4He eta Reaction Near Threshold

摘要： 反应$dd\rightarrow \,^4\!H\!e\,\eta$在阈值附近的截面在两步模型中被估算，类似于成功描述近阈值$pd\rightarrow \,^3\!H\!e\,\eta$产生的模型。 一个$\pi$介子在靶氘核的一个核子上的$dp\rightarrow \,^3\!H\!e\,\pi^o$过程中产生，通过另一个核子上的二次$\pi^o n \to n\,\eta$反应转化为一个$\eta$介子。 运动学条件使得这两个过程几乎为真实过程，因此只需要较小的费米动量。 该模型的预测与最近萨克雷实验数据有良好一致。 一个类似的模型，当应用于近阈值$n\,^3\!H\!e\rightarrow \,^4\!H\!e\,\eta$反应时，预测了一个相当大小的截面，但实验上的困难使得这成为研究$\eta\, ^4\!H\!e$相互作用的一种可疑手段。 显示英文摘要

摘要： The cross section for the reaction $dd\rightarrow \,^4\!H\!e\,\eta$ close to threshold is estimated in a two-step model, similar to that which successfully describes near-threshold $pd\rightarrow \,^3\!H\!e\,\eta$ production. A $\pi$-meson, created in a $dp\rightarrow \,^3\!H\!e\,\pi^o$ process on one nucleon in the target deuteron, is converted into an $\eta$-meson by a secondary $\pi^o n \to n\,\eta$ reaction on the other nucleon. The kinematics are such that both processes are nearly physical so that only small Fermi momenta are required. The predictions of the model are in good agreement with recent Saclay experimental data. An analogous model, when applied to the near-threshold $n\,^3\!H\!e\rightarrow \,^4\!H\!e\,\eta$ reaction, predicts a cross section of a rather similar size, but experimental difficulties render this a doubtful means of studying the $\eta\, ^4\!H\!e$ interaction.