Experimental Test of the Impulse Approximation inpdInelastic Scattering at 200 MeV

Abstract

Inelastic pd interactions have been studied at 200 MeV by bombarding a target of liquid deuterium with a 92% polarized proton beam. The directions and energies of the two scattered protons were measured using thick plastic scintillation counters. Four types of cross sections were studied: (1) the two-proton coincidence rate, $\frac{d\ensuremath{\sigma}}{d{\ensuremath{\Omega}}_{1}}d{\ensuremath{\Omega}}_{2}$; (2) the fully differential cross section, $\frac{d\ensuremath{\sigma}}{d{\ensuremath{\Omega}}_{1}d{\ensuremath{\Omega}}_{2}d{E}_{1}}$; (3) the single-arm charged-particle yield, $\frac{d\ensuremath{\sigma}}{d{\ensuremath{\Omega}}_{1}}$; and (4) "singlet deuteron" production. These measured cross sections, and previously reported 145-MeV data of Knuckes et al., are compared with impulse-approximation theories. Our treatment of the spectator model differs from that used previously in that we have treated the kinematics relativistically. The first two cross sections are dominated by quasifree $pp$ scattering. Impulse theories which include final-state interaction terms give much better fits to these data than the simple spectator model gives, but there remains an overestimation of the observed cross section in the quasifree $pp$ region of about 10%, and the fit in other regions is still qualitative only. The single-arm yield is described very well by a simple sum rule giving the yield as the sum of the free $pp$ and $pn$ differential cross sections. A final-state-interaction enhancement in the two-proton rate, usually referred to as the "singlet deuteron," was observed in the region of ${105}^{0}$ c.m. $\mathrm{pd}$ elastic scattering having a cross section of 0.3 mb/${\mathrm{sr}}^{2}$.