A tagged medium-energy neutron beam has been used in a precise measurement of the absolute differential cross section for np back-scattering. The results resolve significant discrepancies within the np database concerning the angular dependence in this regime. The experiment has determined the absolute normalization with 1.5% uncertainty, suitable to verify constraints of supposedly comparable precision that arise from the rest of the database in partial wave analyses. The analysis procedures, especially those associated with evaluation of systematic errors in the experiment, are described in detail so that systematic uncertainties may be included in a reasonable way in subsequent partial wave analysis fits incorporating the present results.
Final differential cross sections averaged over data samples.
We report the results of an experiment which measured n-p elastic scattering differential cross sections over a range in -t from 0.15 to ~ 3.6 (Gev/c)2 for incident neutron momenta from 70 to 400 GeV/c. We find the logarithmic slope parameter, evaluated at -t = 0.2 (GeV/c)2, to be consistent with existing proton-proton parameterizations. The data exhibit a dip in the cross section near -t 1.4 (Gev/c)2 for incident neutron momenta above 200 Gev/c. For neutron momenta less than 280 GeV/c, the neutron-proton cross sections are found to be higher than existing proton-proton data in the range 0.7 ~ -t ~ 1.3 (Gev/c)2 which is in contradic- tion to most Regge predictions.
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