  Diffractive dissociation reactions studied at the COMPASS experiment at CERN
provide access to the light-meson spectrum. During a pilot run in 2004, using a
pion beam and a lead target, 420k \pi- \pi- \pi+ final-state events with masses
below 2.5 GeV/c2 were recorded, yielding a significant spin-exotic signal for
the controversial \pi 1(1600) resonance. After a significant upgrade of the
spectrometer in 2007, the following two years were dedicated to meson
spectroscopy. Using again a pion beam, but now with a liquid hydrogen target,
an unique statistics of ~60M events of the same final state was gathered in
2008. During a short campaign in 2009, the H2 target was exchanged by several
solid state targets in order to compare final states produced on targets with
different atomic numbers. A partial-wave Analysis (PWA) was performed on all
these data sets and results are presented.
