Two-Pion production in the second resonance region in $\ddot{I}{€}^{-}p$ collisions with HADES

Abstract

Pion induced reactions provide unique opportunities for an unambiguous description of baryonic resonances and their coupling channels by means of a partial wave analysis. Using the secondary pion beam at SIS18, the two pion production in the second resonance region has been investigated to unravel the role of the $N(1520){\frac{3}{2}}^{-}$ resonance in the intermediate $\ddot{I}$ production. Results on exclusive channels with one pion ($\ddot{I}{€}^{-}p$) and two pions ($\ddot{I}{€}^{+}\ddot{I}{€}^{-}n$, $\ddot{I}{€}^0\ddot{I}{€}^{-}p$) in the final state measured in the $\ddot{I}{€}^{-}-p$ reaction at four different pion beam momenta (0.650, 0.685, 0.733, and 0.786 GeV/c) are presented. The excitation function of the different partial waves and $\hat{I}”\ddot{I}€$, $N\ddot{I}ƒ$ and $N\ddot{I}$ isobar configurations is obtained, using the Bonn-Gatchina partial wave analysis. The $N(1520){\frac{3}{2}}^{-}$ resonance is found to dominate the $N\ddot{I}$ final state with the branching ratio $BR=12.2\pm 1.9\%$.