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HK: Fachverband Physik der Hadronen und Kerne
HK 19: Hadron Structure and Spectroscopy 4
HK 19.6: Talk
Monday, March 23, 2015, 18:45–19:00, T/SR25
On the nature of the a1(1420) — •Mikhail Mikhasenko, Bernhard Ketzer, and Andrey Sarantsev — Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, Bonn, Germany
The resonance-like signal with axial-vector quantum numbers in the f0(980) π system, recently observed by the COMPASS and VES experiments at a mass of 1420 MeV, is discussed. We interpret it as a "pseudo resonance" due to a logarithmic singularity arising in the reaction a1−(1260)→ K⋆− K0+K⋆ 0 K−→ f0(980) π−. The triangle diagram corresponding to this process is calculated. The structure of the imaginary part of the amplitude is investigated by employing the Cutkosky cutting rules. The result exhibits a peak in the intensity of the a1(1260) → f0 π P-wave with a sharp phase motion with respect to the dominant ρ π S-wave decay, in good agreement with data. The branching ratio for the decay of a1(1260)→ f0(980)π is estimated and compared to the a1(1260)→ρπ decay.