X-rays from proton-antiproton annihilation into charged final states☆

Abstract X-rays originating in the deexcitation of pp atoms and their subsequent annihilation into two charged and any number of neutral mesons have been measured with a position and energy-sensitive drift proportional chamber. The atomic L-lines and the inner bremsstrahlung are clearly observed. The theoretically predicted differential probability for production of inner bremsstrahlung is confirmed. Additional features in the X-ray spectrum are attributed to K-lines and a nearly flat background which is probably due to Compton scattering in the detector of higher energy X- and γ-rays. The absolute yield of L-lines per antiproton stop is Y L =0.11 (2), the corresponding value for K-lines is K K = 0.0014 (6).