$^3$ He双介子聚变中的ABC效应和共振结构
ABC Effect and Resonance Structure in the Double-Pionic Fusion to $^3$He
摘要：
在所谓的ABC效应的能量区域中对$^3$ He的双π介子融合进行了排他性和运动学上完整的测量，这表示在$ππ$不变质谱中有明显的低质量增强。实验是在COSY的WASA探测器上进行的。与基本$pn \to d π^0π^0$反应和$dd \to ^4$ He $π^0π^0$反应中的观察结果类似，数据揭示了ABC效应和总截面中共振样能量依赖性之间的相关性。微分截面很好地描述了假设的$d^*$共振形成的反应过程中，除了传统的$t$通道$ΔΔ$机制。推导出的$d^*$共振宽度可以从初核和终核中核子的费米运动引起的碰撞增宽来理解。
英文摘要：
Exclusive and kinematically complete measurements of the double pionic fusion to $^3$He have been performed in the energy region of the so-called ABC effect, which denotes a pronounced low-mass enhancement in the $ππ$-invariant mass spectrum. The experiments were carried out with the WASA detector setup at COSY. Similar to the observations in the basic $pn \to d π^0π^0$ reaction and in the $dd \to ^4$He$π^0π^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. Differential cross sections are well described by the hypothesis of $d^*$ resonance formation during the reaction process in addition to the conventional $t$-channel $ΔΔ$ mechanism. The deduced $d^*$ resonance width can be understood from collision broadening due to Fermi motion of the nucleons in initial and final nuclei.
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