Baryonic resonances close to the (K)over-barN threshold: The case of Λ (1405) in pp collisions

We present an analysis of the Lambda(1405) resonance produced in the reaction p + p -> Sigma(+/-) + pi(-/+) + K+ + p at 3.5 GeV kinetic beam energy measured with the High Acceptance Dielectron Spectrometer (HADES) at the Gesellschaft fur Schwerionenforschung (GSI). The two charged decay channels Lambda (1405) -> Sigma(+/-) + pi(-/+) have been reconstructed for the first time in p + p collisions. The efficiency and acceptance- corrected spectral shapes show a peak position clearly below 1400MeV/c(2). We find a total production cross section of sigma(Lambda(1405)) = (1405) = 9.2 +/- 0.9 +/- 0.7(-1.0)(+3.3)mu b . The analysis of its polar angle distribution suggests that the Lambda(1405) is produced isotropically in the p - p center-of-mass system (CMS). DOI: 10.1103/ PhysRevC.87.025201