Two-pion production in the second resonance region in ${\ensuremath{\pi}}^{\ensuremath{-}}p$ collisions with the High-Acceptance Di-Electron Spectrometer (HADES)

Two-pion production in the second resonance region in $π^{-} p$ collisions with the High-Acceptance Di-Electron Spectrometer (HADES)

J. Adamczewski-Musch et al. (HADES Collaboration )

Phys. Rev. C 102, 024001 – Published 7 August 2020

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 $ρ$ -meson production. Results on exclusive channels with one pion ( $π^{-} p$ ) and two pions ( $π^{+} π^{-} n$ , $π^{0} π^{-} p$ ) in the final state measured in the $π^{-} − p$ 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 $Δ π$ , $N σ$ , and $N ρ$ isobar configurations is obtained, using the Bonn-Gatchina partial-wave analysis. The $N (1520) {\frac{3}{2}}^{-}$ resonance is found to dominate the $N ρ$ final state with the branching ratio $BR = 12.2 % \pm 1.9 %$ .