The 90° differential cross section for charged meson production in hydrogen and carbon is measured for incident proton energies 345 to 380 Mev. For hydrogen, the 90° ${\pi }^{+}$} meson production energy spectra occur as peaks in the energy region predicted from the kinematics of the reaction $p+p\to {\pi }^{+}+d$. Ratios of these 90° ${\pi }^{+}$ differential cross sections are $\frac{\left(d\sigma \right)}{\left(d\omega \right)}$ at 380 Mev: $\frac{\left(d\sigma \right)}{\left(d\omega \right)}$ at 365 Mev: $\frac{\left(d\sigma \right)}{\left(d\omega \right)}$ at 345 Mev=2.6:1.6:1 with a statistical uncertainty of 15 percent. For carbon the ${\pi }^{+}$ meson production spectra show an increase in the energy of the maximum of the broad distributions, with increasing incident proton energy. The $\frac{\left({\pi }^{+}\right)}{\left({\pi }^{-}\right)}$ ratio in carbon is found to be in the range (10±3): 1 for all three proton energies studies. Qualitative agreement with these carbon ${\pi }^{+}$ meson spectra is obtained from a phenomenological analysis based upon the assumptions of nucleon-nucleon collisions in which the target has a Gaussian momentum distribution.

• Received 10 September 1952

DOI:https://doi.org/10.1103/PhysRev.88.1247