Measurement of antineutron-proton total and annihilation cross sections from 100 to 500 MeV/c

Total and annihilation n-barp cross sections from 100 to 500 MeV/c are reported, the first such measurements with good statistics in this momentum range. These cross sections are well represented by A+B/p, where p is the incident antineutron momentum, and are in agreement with previous n-barp and p-barn measurements. A comparison of these cross sections with phenomenological potential model calculations is good overall. However, the microscopic quark model gives unsatisfactory predictions. The agreement between previous p-barp annihilation cross sections and n-barp cross sections above 300 MeV/c is excellent. The total n-barp cross section is lower than the total p-barp cross section in this momentum range. Both of these types of behavior are predicted by potential models. The anticipated availability of future p-barp data below 300 MeV/c should indicate whether these trends continue at lower momenta.