  The reaction ${n} {p} \to {p} {p} \pi^{-}$ has been studied in a
kinematically complete measurement with a large acceptance time-of-flight
spectrometer for incident neutron energies between threshold and 570 MeV. The
proton-proton invariant mass distributions show a strong enhancement due to the
pp($^{1}{S}_{0}$) final state interaction. A large anisotropy was found in the
pion angular distributions in contrast to the reaction ${p}{p} \to {p}{p}
\pi^{0}$. At small energies, a large forward/backward asymmetry has been
observed. From the measured integrated cross section $\sigma({n}{p} \to {\rm
p}{p} \pi^{-})$, the isoscalar cross section $\sigma_{01}$ has been extracted.
Its energy dependence indicates that mainly partial waves with Sp final states
contribute. Note: Due to a coding error, the differential cross sections ${d
\sigma}/{d M_{pp}}$ as shown in Fig. 9 are too small by a factor of two, and
inn Table 3 the differential cross sections ${d \sigma}/{d \Omega_{\pi}^{*}}$
are too large by a factor of $10/2\pi$. The integrated cross sections and all
conclusions remain unchanged. A corresponding erratum has been submitted and
accepted by European Physics Journal.
