Study of Few-Body Problems at WASA — the ABC Phenomenon
Physikalisches Institut der Universitāt Tübingen, Auf der
Morgenstelle 14, D-72076
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A short overview over the ongoing few-body program at WASA@COSY is given with special emphasis on the ABC phenomenon, which is known since 50 years without having found a consistent explanation. We show that this phenomenon is linked with a resonant energy dependence in the total cross section of isoscalar double-pionic fusion processes. This resonance structure is connected with the baryon-baryon system, in particular with the pn and ∆∆ systems, however, possesses a mass, which is 90 MeV below the nominal ∆∆ threshold and has a width of only 50 MeV, i. e., ﬁve times smaller than expected from a conventional t-channel ∆∆ process.
© Owned by the authors, published by EDP Sciences, 2010