Measurement of the total and differential cross sections for the reaction π − p → ηn with the Crystal Ball detector

The first results obtained in 1998 by the Crystal Ball collaboration from a measurement of the total and differential cross sections for the reaction π − p → ηn are presented. These new experimental results for the total cross sections are compared with the predictions of the K -matrix model for pion-nucleon scattering. The angular distribution at momenta near the reaction threshold (685 MeV/ c ) is determined by the S -wave contribution. The P -wave contribution begins to manifest itself from a momentum of 720 MeV/ c .