Abstract
We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction over the full energy region of the ABC effect, a pronounced low-mass enhancement in the -invariant mass spectrum. The measurements, which cover also the transition region to the conventional -channel process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with , and in both and systems. Necessary further tests of the resonance interpretation are discussed.
- Received 1 April 2011
DOI:https://doi.org/10.1103/PhysRevLett.106.242302
© 2011 American Physical Society