Meson Spectroscopy and Search for Spin-Exotic States at COMPASS

This paper presents the results of a partial wave analysis of about 420 000 diffractive dissociation events with four-momentum transfer $t'\in$ [0.1, 1] GeV$^{2}/c^{2}$. The data were recorded at COMPASS during a short pilot run in 2004, using a 190GeV$/c$ negative pion beam on lead targets. Reactions of the type $\pi^{-}N\rightarrow\pi^{-}\pi^{-}\pi^{+}N'$ have been investigated and resonances up to 2.5 GeV$/c^{2}$ have been searched for. In addition to well-known mesons, also a state with spin-exotic quantum numbers $J^{PC} =$ 1$^{−+}$ is observed.