Double-Pionic Fusion of Nuclear Systems and the 'ABC' Effect: Approaching a Puzzle by Exclusive and Kinematically Complete Measurements
- Physikalisches Institut der Universitaet Tuebingen, D-72076 Tuebingen (Germany)
- Department of Physics, Stockholm University, Stockholm (Sweden)
- Soltan Institute of Nuclear Studies, Warsaw and Lodz (Poland)
- Joint Institute for Nuclear Research, Dubna (Russian Federation)
The ABC effect--a puzzling low-mass enhancement in the {pi}{pi} invariant mass spectrum, first observed by Abashian, Booth, and Crowe--is well known from inclusive measurements of two-pion production in nuclear fusion reactions. Here we report on the first exclusive and kinematically complete measurements of the most basic double-pionic fusion reaction pn{yields}d{pi}{sup 0}{pi}{sup 0} at beam energies of 1.03 and 1.35 GeV. The measurements, which have been carried out at CELSIUS-WASA, reveal the ABC effect to be a ({pi}{pi}){sub I=L=0} channel phenomenon associated with both a resonancelike energy dependence in the integral cross section and the formation of a {delta}{delta} system in the intermediate state. A corresponding simple s-channel resonance ansatz provides a surprisingly good description of the data.
- OSTI ID:
- 21180180
- Journal Information:
- Physical Review Letters, Vol. 102, Issue 5; Other Information: DOI: 10.1103/PhysRevLett.102.052301; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0031-9007
- Country of Publication:
- United States
- Language:
- English
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