Model dependence of the $\pi_1(1600)\to\rho(770)\pi$ signal

Using the large C OMPASS data set on diffractive three pion production, we investigate the contradictory observations reported by previous experiments on the existence of a resonance signal in the spin-exotic wave with spin, parity and charge conjugation quantum numbers 1−+ . We identify a strong dependence of the result on the employed analysis model as the cause and derive a model tuned to minimize these effects. Additionally, we study the robustness of our analysis model using the approach of freed-isobar partial-wave analysis.