Deuteron breakup at 2.1 and 1.25 GeV

Inclusive differential cross section and analyzing power $T_{20}$ in A(d,p)X at 2.1 GeV and for protons at 0° 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 π rescattering, Δ excitation, and a six quark component in the deuteron.