Two-pion production in nucleon-nucleon collisions鈥擝ack to dibaryons?

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• 作者：H. Clement ^{clement@pit.physik.uni-tuebingen.de}
• 关键词：Two-pion production ; Nucleon&ndash ; nucleon collisions ; Baryon&ndash ; baryon systems ; Dibaryon resonance ; ABC effect
• 刊名：Progress in Particle and Nuclear Physics
• 出版年：2012
• 期刊代码：64_01466410
• 类别：ph
• 出版时间：April, 2012
• 卷：67
• 期：2
• 页码：486-490
• 文件大小：340 K

摘要

The two-pion production in nucleon-nucleon collisions has been investigated systematically by exclusive and kinematically complete measurements at CELSIUS/WASA and more recently at COSY-TOF and particularly WASA@COSY. The data for all -induced isovector production channels in the energy range from threshold up to = 1.4聽GeV can be well understood by -channel Roper, and possibly excitation. In contrast to that the purely isoscalar reaction channel exhibits a narrow resonance-like structure with and in the total cross section, which is correlated with an intriguing low-mass enhancement in the invariant mass spectrum (ABC effect) as well as with the formation of a system in the intermediate state. From the angular distributions the spin and parity of this structure have been derived resulting in . The consequences of the resonance hypothesis for other reaction channels are discussed. The fact that also the double-pionic fusion reactions to ³He and ⁴He exhibit a corresponding resonance-like structure in the total cross section correlated with the ABC effect suggests that the underlying conjectured resonance is obviously robust enough to survive in nuclei.