The reaction {n} {p} \to {p} {p} π^{-} from threshold up to 570 MeV
M. Daum, M. Finger, M. Finger Jr., J. Franz, F.H. Heinsius, A. Janata, K. Königsmann, H. Lacker, F. Lehar, H. Schmitt, W. Schweiger, P. Sereni, M. Slune?ka
Abstract
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.