C12(p,pn)C11cross section at 300 GeV

The absolute cross section for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}\mathrm{}(p,pn)\mathrm{}{}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ reaction has been measured in the $M2\mathrm{}$ diffracted proton beam of the Fermi National Accelerator Laboratory at an energy of 300 GeV. Proton intensities were measured with a scintillation counter telescope, and the 20.4-min ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ activity induced in 3.2-mm thick plastic scintillator targets was determined both by internal scintillation ($\beta$) counting and by annihilation radiation counting with a NaI well crystal. A correction for the formation of ${}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ by secondary particles was determined by measuring the activity in individual targets in a stack. The corrected value for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}\mathrm{}(p,pn)\mathrm{}{}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ cross section at 300 GeV is 24.6 ± 1.6 mb.