Deuteron breakup at 2.1 and 1.25 GeV

Abstract

Inclusive differential cross section and analyzing power ${T}_{20}$ in A(d,p)X at 2.1 GeV and for protons at 0\ifmmode^\circ\else\textdegree\fi{} are presented for the targets $^{1}\mathrm{H}$, $^{4}\mathrm{He}$, $^{12}\mathrm{C}$, Ti, and Sn. In addition, data for $^{1}\mathrm{H}$ at 1.25 GeV are also shown. For all targets the cross-section data show a similarity in shape when plotted as a function of q, the proton momentum in the deuteron frame, each target exhibiting a shoulder near q=0.30--0.35 GeV/c. Likewise, ${T}_{20}$ values are largely independent of the target's A value. When compared with higher-energy data for $^{12}(\mathit{d}$,p)X, the new results establish the universality of the shoulder over the energy range 1.25--7.4 GeV, as well as the energy independence of ${T}_{20}$. The $^{1}(\mathit{d}$,p)X data are compared with the results of a nonrelativistic calculation of the six lowest-order graphs of the process using elastic, on-shell NN amplitudes and the Paris NN potential deuteron wave function. The calculated cross sections have no shoulder at either of the two energies of this experiment; the observed behavior of ${T}_{20}$ is reproduced qualitatively only. Comparisons with $^{2}(\mathit{p}$,2p) and $^{2}(\mathit{e}$,e'p) data are made and various possible origins for the anomalous shoulder discussed, including \ensuremath{\pi} rescattering, \ensuremath{\Delta} excitation, and a six quark component in the deuteron.