Baryonic resonances close to the $\bar{K}N$ threshold: the case of $\Lambda$(1405) in $pp$ collisions

Abstract

We present an analysis of the Λ(1405) resonance produced in the reaction p+p→Σ±+π∓+K++p at 3.5GeV kinetic beam energy measured with the High Acceptance Dielectron Spectrometer (HADES) at the Gesellschaft für Schwerionenforschung (GSI). The two charged decay channels Λ(1405)→Σ±π∓ 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/c2. We find a total production cross section of σΛ(1405)=9.2±0.9±0.7−1.0+3.3μb. The analysis of its polar angle distribution suggests that the Λ(1405) is produced isotropically in the p−p center-of-mass system (CMS).