Two-pion production in the second resonance region in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mi>π</mml:mi><mml:mo>−</mml:mo></mml:msup><mml:mi>p</mml:mi></mml:mrow></mml:math> collisions with the High-Acceptance Di-Electron Spectrometer (HADES)

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 $N(1520){\frac{3}{2}}^{\ensuremath{-}}$resonance in the intermediate $\ensuremath{\rho}$-meson production. Results on exclusive channels with one pion (${\ensuremath{\pi}}^{\ensuremath{-}}p$) and two pions (${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}n$, ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}p$) in the final state measured in the ${\ensuremath{\pi}}^{\ensuremath{-}}\text{\ensuremath{-}}p$ 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 $\mathrm{\ensuremath{\Delta}}\ensuremath{\pi}$, $N\ensuremath{\sigma}$, and $N\ensuremath{\rho}$ isobar configurations is obtained, using the Bonn-Gatchina partial-wave analysis. The $N(1520){\frac{3}{2}}^{\ensuremath{-}}$ resonance is found to dominate the $N\ensuremath{\rho}$ final state with the branching ratio $\text{BR}=12.2%\ifmmode\pm\else\textpm\fi{}1.9%$.

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