Resonance production and ππ S -wave in π-+p →π-π-π++p recoil at 190 GeV/c

The COMPASS collaboration has collected the currently largest data set on diffractively produced π-π-π+ final states using a negative pion beam of 190 GeV/c momentum impinging on a stationary proton target. This data set allows for a systematic partial-wave analysis in 100 bins of three-pion mass, 0.5<m3π<2.5 GeV/c2, and in 11 bins of the reduced four-momentum transfer squared, 0.1<t′<1.0 (GeV/c)2. This two-dimensional analysis offers sensitivity to genuine one-step resonance production, i.e. the production of a state followed by its decay, as well as to more complex dynamical effects in nonresonant 3π production. In this paper, we present detailed studies on selected 3π partial waves with JPC=0-+, 1++, 2-+, 2++, and 4++. In these waves, we observe the well-known ground-state mesons as well as a new narrow axial-vector meson a1(1420) decaying into f0(980)π. In addition, we present the results of a novel method to extract the amplitude of the π-π+ subsystem with IGJPC=0+0++ in various partial waves from the π-π-π+ data. Evidence is found for correlation of the f0(980) and f0(1500) appearing as intermediate π-π+ isobars in the decay of the known π(1800) and π2(1880).