Natural parity resonances in ηπ+π−

Abstract

Results of a partial wave analysis of the ηπ + π − final state are presented using 4.2×10 4 events with | t|<0.2 GeV 2, collected at the VES setup; the reaction is π − p→ π − π + ηn from a beryllium target. The data reveal resonant structures, which are identified by phase motion as well as peaks in intensities of partial waves. The f 2(1565) meson, also called the AX meson, is observed in decays to [ a 2(1302) π] L=1 . The parameters obtained from a fit with a Breit–Wigner amplitude are M=1550±20 MeV with Γ=130±40 MeV. The higher mass f 2 resonances are also discussed. For J P =3 −, the well known ρ 3(1690) is seen in decays to both a 2(1320) π and ρη channels. The complex behaviour of 3 −− amplitudes at higher masses is described best by introducing two additional resonant poles near 2.14 and 2.30 GeV. There is evidence for an f 4(2300) meson, decaying dominantly to [ f 2 η] L=3 .