Proton-Neutron Elastic Scattering on a Deuterium Target

Abstract

We have tested the feasibility of measuring the ratio of proton-neutron to proton-proton elastic scattering using the second extracted proton beam of the Argonne ZGS and a liquid-deuterium target. The forward proton was detected by a 35-m-long spectrometer consisting of magnets and scintillation and \ifmmode \check{C}\else \v{C}\fi{}erenkov counters. The recoil nucleon was detected by a steel-scintillator sandwich counter. The efficiency of this counter was measured using tagged neutron in coincidence with the spectrometer and calculated using a Monte Carlo simulation of the nuclear cascade. A scintillation counter determined whether the recoil nucleon was charged or neutral. At a test point of ${p}_{0}=12.4$ GeV/c, ${\ensuremath{\theta}}^{*}=37\ifmmode^\circ\else\textdegree\fi{}$, and $t=\ensuremath{-}2.2$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, we found a $\mathrm{pn}$-to-$\mathrm{pp}$ cross-section ratio of 1.05\ifmmode\pm\else\textpm\fi{}0.14. The $\mathrm{pp}$ cross section was ${(\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}})}_{\mathrm{c}.\mathrm{m}.}=5.8\ifmmode\pm\else\textpm\fi{}0.6$ \ensuremath{\mu}b/sr, and the $\mathrm{pn}$ cross section was ${(\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}})}_{\mathrm{c}.\mathrm{m}.}=6.1\ifmmode\pm\else\textpm\fi{}1$ \ensuremath{\mu}b/sr. The ratio of $\mathrm{pp}$ scattering from deuterium to $\mathrm{pp}$ scattering from hydrogen, corrected for geometrical effects, was 0.75\ifmmode\pm\else\textpm\fi{}0.09. We discuss the future of this technique for measuring $\mathrm{pn}$ cross sections and compare the results of the test with the predictions of the Glauber multiple-scattering formalism. We also plot available $\mathrm{pn}$ data as a function of ${{\ensuremath{\beta}}_{\mathrm{c}.\mathrm{m}.}}^{2}{{p}_{\ensuremath{\perp}}}^{2}$.