Nature of the a1(1420)

M. Mikhasenko, B. Ketzer, and A. Sarantsev
Phys. Rev. D 91, 094015 – Published 14 May 2015

Abstract

The resonancelike signal with axial-vector quantum numbers JPC=1++ at a mass of 1420 MeV and a width of 140 MeV, recently observed by the COMPASS and VES experiments in the f0(980)π final state and tentatively called a1(1420), is discussed. Instead of a genuine new meson, we interpret this signal as a dynamical effect due to a singularity (branching point) in the triangle diagram formed by the processes a1(1260)KK¯, KKπ, and KK¯f0(980) (+c.c). The amplitude for this diagram is calculated. The result exhibits a peak in the intensity with a sharp phase motion with respect to the dominant a1(1260)ρπ S-wave decay, in good agreement with the data. The branching ratio of a1(1260)f0(980)π via the triangle diagram is estimated and compared to the dominant decay a1(1260)ρπ.

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  • Received 17 March 2015

DOI:https://doi.org/10.1103/PhysRevD.91.094015

© 2015 American Physical Society

Authors & Affiliations

M. Mikhasenko1, B. Ketzer1,*, and A. Sarantsev1,2

  • 1Universität Bonn, Helmholtz-Institut für Strahlen- und Kernphysik, 53115 Bonn, Germany
  • 2NRC Kurchatov Institute, PNPI, 188300, Gatchina, Russia

  • *Bernhard.Ketzer@uni-bonn.de

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Vol. 91, Iss. 9 — 1 May 2015

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