Backward np Scattering With a Polarized Target

The authors have measured the polarization parameter P in neutron-proton elastic scattering near the backward direction, using a polarized proton target. Measurements covered the range of incident neutron moment from 1.0 to 5.5 GeV/c and of four-momentum transfer squared u from -0.005 to -0.5 (GeV/c){sup 2}. Forward going protons were detected by means of a wire-spark-chamber spectrometer. Slow neutrons near 90 deg lab angle were detected in coincidence by means of an array of plastic scintillation counters. P was determined from the change in counting rate I of scattered particles upon reversal of the target polarization P{sub T} according to I = I{sub 0}[l + P(P{sub T} {center_dot} k incident neutron x k final neutron/sin {theta} final neutron)]. They find that P is consistently negative and shows no marked structure as a function of u and of incident momentum. The data roughly follow the simple form P = -0.5 {radical}-u/m{sub p}