Natural parity resonances in ηπ+π− Original Research Article

Results of a partial wave analysis of the ηπ+π− final state are presented using 4.2×104 events with |t|<0.2 GeV2, 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 f2(1565) meson, also called the AX meson, is observed in decays to [a2(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 f2 resonances are also discussed. For JP=3−, the well known ρ3(1690) is seen in decays to both a2(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 f4(2300) meson, decaying dominantly to [f2η]L=3.