Unitarity approach to the mass-dependent fit of $3π$ resonance production data from the COMPASS experiment

Abstract

We derive a unitarized model for the peripheral production of the three-pion system in the isobar approximation. The production process takes into account long-range t-channel pion exchange. The K-matrix approach is chosen for the parameterization of the scattering amplitude. Five coupled channels are used to fit the COMPASS spin-density matrices for the J$^{PC}$ M$^ϵ$ = 2$^{−+}$0$^+$ sector. Preliminary results of the fit are presented.