Neutron-proton analyzing power measurements from 375 to 775 MeV

As part of an experimental study of the nucleon-nucleon interaction at medium energy, the free neutron-proton analyzing power $A_n$(${\theta }_n^{\mathrm{*}}$,$T_n$) has been measured at nine incident neutron energies in the range 375≤$T_n$≤775 MeV and for neutron c.m. angles in the range 57°≤${\theta }_n^{\mathrm{*}}$≤159°. Unpolarized neutrons with a broad continuum of energies, produced by interaction of an 800 MeV proton beam with a beryllium target, were scattered from a polarized proton target. At each angle, for the whole energy region, the scattered neutron and conjugate recoil proton were detected in coincidence. A previously unseen minimum is observed in the energy dependence of $A_n$(${\theta }^{\mathrm{*}}$∼100°) near 625 MeV.