4 He双π聚变中的ABC共振结构
ABC Resonance Structure in the Double-Pionic Fusion to 4He
摘要：
在0.8 - 1.4 GeV能量范围内对双π介子聚变反应$dd \to ^4$ He $π^0π^0$进行了排他性的和运动学上完全的高统计测量，从而覆盖了ABC效应的区域，这表明在$ππ$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$pn \to d π^0π^0$反应中的观察结果相似，数据揭示了ABC效应和总截面中的共振样能量依赖性之间的相关性。最大值出现在m=2.37 GeV + 2 $m_N$处，即与碱性反应中相同的位置。观察到的共振宽度$Γ\approx$ 160 MeV可以理解的加宽由于费米运动的核子在初始和最终的核与碰撞阻尼。微分截面同样很好地描述了一个$pn$共振形成在反应过程中的假设。
英文摘要：
Exclusive and kinematically complete high-statistics measurements of the double pionic fusion reaction $dd \to ^4$He$π^0π^0$ have been performed in the energy range 0.8 - 1.4 GeV covering thus the region of the 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 observation in the basic $pn \to d π^0π^0$ reaction, the data reveal a correlation between the ABC effect and a resonance-like energy dependence in the total cross section. The maximum occurs at m=2.37 GeV + 2$m_N$, i.e. at the same position as in the basic reaction. The observed resonance width $Γ\approx$ 160 MeV can be understood from broadening due to Fermi motion of the nucleons in initial and final nuclei together with collision damping. Differential cross sections are described equally well by the hypothesis of a $pn$ resonance formation during the reaction process.
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