核系统的双π聚变和ABC效应--用排斥和运动学完全测量方法探索一个难题
Double-Pionic Fusion of Nuclear Systems and the ABCEffect -- Aproaching a Puzzle by Exclusive and Kinematically Complete Measurements
摘要：
ABC效应--$ππ$不变质谱中令人困惑的低质量增强--在核聚变反应中对2 π介子产生的包容性测量中是众所周知的。在这里，我们报告的第一次独家和运动学上完整的测量最基本的双介子融合反应$pn \to d π^0π^0$在1.03和1.35 GeV。的测量，这已经进行了在CELSIUS-WASA，揭示了ABC效应是一个$(ππ)_{I=L=0}$通道现象与一个共振类能量依赖的积分截面和形成的$ΔΔ$系统在中间状态。一个相应的简单的s-通道共振分析提供了一个令人惊讶的良好的数据描述。
英文摘要：
The ABC effect - a puzzling low-mass enhancement in the $ππ$ invariant mass spectrum - is well-known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on first exclusive and kinematically complete measurements of the most basic double pionic fusion reaction $pn \to d π^0π^0$ at 1.03 and 1.35 GeV. The measurements, which have been carried out at CELSIUS-WASA, reveal the ABC effect to be a $(ππ)_{I=L=0}$ channel phenomenon associated with both a resonance-like energy dependence in the integral cross section and the formation of a $ΔΔ$ system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data.
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