Observation of the a4(2040) and a radial excitation of the a2(1320) decaying into ηπ− Original Research Article

Preliminary results from the E852 experiment are given. A mass dependent partial wave analysis of the reaction π−p → ηπ−p → γγπ−p has been carried out in the ηπ− mass range 0.7 GeV/c2 through 2.5 GeV/c2. This analysis is based on 60K events. The experimental data was collected with the E852 setup at the AGS accelerator during the 1995 run. A resonance with JP = 4+ and IG = 1− is observed in the G+-wave. The mass and width of this state are M = 2037−17+19MeV/c2 and Γ = 401−59+70MeV/c2 respectively. In addition, a resonant structure has been observed in the D+-wave. This can be interpreted as a radial excitation of the a2(1320) with mass M = 1637−23+33MeV/c2 and width Γ = 226−49+51MeV/c2.