Low-mass pi pi enhancement in baryonic pi pi production: ABC effect revised by exclusive measurements

M. Bashkanov*, O. Khakimova, T. Skorodko, C. Bargholtz, D. Bogoslowsky, H. Calen, F. Cappellaro, H. Clement, C. Ekstroem, K. Fransson, L. Geren, L. Gustafsson, B. Hoeistad, G. Ivanov, M. Jacewicz, E. Jiganov, T. Johansson, M. M. Kaskulov, S. Keleta, I. KochF. Kren, S. Kullander, A. Kupsc, A. Kuznetsov, K. Lindberg, P. Marciniewski, R. Meier, B. Morosov, W. Oelert, C. Pauly, Y. Petukhov, A. Povtoreyko, R. J. M. Y. Ruber, A. Schwick, W. Scobel, R. Shafigullin, B. Shwartz, V. Sopov, J. Stepaniak, P. -E. Tegner, V. Tchernyshev, P. Thoerngren-Engblom, V. Tikhomirov, A. Turowiecki, G. J. Wagner, M. Wolke, A. Yamamoto, J. Zabierowskin, I. Zartova, J. Z. Loman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The ABC effect - a puzzling threshold enhancement in the pi pi invariant mass spectrum of double-pionic fusion to nuclear bound states - has been investigated since 40 years by inclusive measurements without providing a conclusive interpretation. First exclusive measurements to this topic have now been carried out at CELSIUS-WASA. They confirm a huge pi pi threshold enhancement, prove it to be of scalar-isoscalar nature, i.e., a sigma-channel phenomenon and reveal the theoretically predicted high-mass enhancement in inclusive spectra to be of pi pi pi rather than of pi pi nature - falsifying thus corresponding model predictions for the ABC effect. From the kinematically complete data samples we infer that the interaction between the two. particles created in this process is of crucial importance.

Original languageEnglish
Pages (from-to)625-628
Number of pages4
JournalInternational Journal of Modern Physics A
Issue number2-3
Publication statusPublished - 30 Jan 2007
Event9th International Workshop on Meson Production, Properties and Internation - Cracow, Poland
Duration: 9 Jun 200613 Jun 2006


  • ABC effect
  • sigma channel enhancement
  • Delta Delta interaction
  • medium effects


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