(π+,p) and (π+,d) reactions on light nuclei

The (${\pi }^{+}$,$p$) and (${\pi }^{+}$,$d$) reactions on $1p$ shell nuclei are studied between $T_{\pi }=32\mathrm{} \mathrm{and} 81$ MeV. Cross sections both to the continuum and to discrete two body final states are given. The spectra and angular distributions of the (${\pi }^{+}$,$p$) continuum are examined in terms of a two-nucleon pion absorption mechanism. The ${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}$(${\pi }^{+}$,$p$) spectra of discrete states are similar to the corresponding ${}_{}{}^{12,13}{}_{}{}^{}\mathrm{C}$($p$,$d$) spectra at the same momentum transfer. The ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(${\pi }^{+}$,$p$)${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$(g.s.) transition is found to have an abnormally small cross section relative to other transitions of similar spectroscopic strength. The two-neutron pickup (${\pi }^{+}$,$d$) data to discrete states is the first published data on this reaction. The (${\pi }^{+}$,$d$) reaction is found to favor strongly transitions in the $1p$ shell of angular momentum transfer $L=2\mathrm{}$. The relative strength of these $L=2\mathrm{}$ transitions varies the same way as the corresponding ($p$,$t$) cross sections. No $L=0\mathrm{}$ transitions are clearly identifiable. The (${\pi }^{+}$,$d$) angular distributions are compared to the calculations of Betz and Kerman. The calculations reproduce well the absolute magnitude and shape of the (${\pi }^{+}$,$d$) angular distributions but fail to predict the $L$ dependence, pion energy dependence, and possibly even the spin transfer dependence of the (${\pi }^{+}$,$d$) cross sections.