Abstract
Historically the double-pionic fusion to 3 He is the reaction, where the ABC effect (low-mass enhancement of the ππ -invariant mass spectrum) was observed for the first time more than 50 years ago. Meanwhile exclusive and kinematically complete high-statistics measurements with WASA at COSY revealed a strict correlation between the ABC effect and a narrow resonance structure with I (J P ) = 0(3+ ) in the total cross section of the most basic double-pionic fusion, the pn → dπ 0 π 0 reaction. In order to investigate the situation in the double-pionic fusion to 3 He the energy dependence of the ABC effect in the fusion to 3 He has been measured by fixed energy measurements of the type pd →3 Heππ as well as by quasifree and coherent measurements of the type dd →3 He n ππ .
Highlights
The ABC effect – an intriguing low-mass enhancement in the ππ invariant mass spectrum – is known from inclusive measurements of two-pion production in nuclear fusion reactions to the few-body systems d, 3He and 4He
Exclusive and kinematically complete highstatistics measurements with WASA at COSY revealed a strict correlation between the ABC effect and a narrow resonance structure with I(JP) = 0(3+) in the total cross section of the most basic double-pionic fusion, the pn → dπ0π0 reaction
In order to investigate the situation in the double-pionic fusion to 3He the energy dependence of the ABC effect in the fusion to 3He has been measured by fixed energy measurements of the type pd →3Heππ as well as by quasifree and coherent measurements of the type dd →3He n ππ
Summary
The ABC effect – an intriguing low-mass enhancement in the ππ invariant mass spectrum – is known from inclusive measurements of two-pion production in nuclear fusion reactions to the few-body systems d, 3He and 4He. The double-pionic fusion to 3He is the reaction, where the ABC effect (low-mass enhancement of the ππ-invariant mass spectrum) was observed for the first time more than 50 years ago.
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