Analysing power for the reaction $\mathrm{np} \rightarrow \mathrm{pp} \pi^{-}$ and for np elastic scattering from 270 to 570 MeV

The analysing power of the reaction ${\rm n} {\rm p} \rightarrow {\rm p} {\rm p} \pi^{-}$ for neutron energies between threshold and 570 MeV has been determined using a transversely polarised neutron beam at PSI. The reaction has been studied in a kinematically complete measurement using a time-of-flight spectrometer with large acceptance. Analysing powers have been determined as a function of the c.m. pion angle in different regions of the proton-proton invariant mass. They are compared to other data from the reactions ${\rm n} {\rm p} \rightarrow {\rm p} {\rm p} \pi^{-}$ and ${{\rm p} {\rm p} \rightarrow {\rm p} {\rm p} \pi^{0}}$ . The np elastic scattering analysing power was determined as a by-product of the measurements.