Laser measurements of the density shifts of resonance lines in antiprotonic helium atoms and stringent constraint on the antiproton charge and mass - Torii,HA; Hayano,RS; Hori,M; Ishikawa,T; Morita,N; Kumakura,M; Sugai,I; Yamazaki,T; Ketzer,B; Hartmann,FJ; von,Egidy T; Pohl,R; et al. (PHYSICAL REVIEW A, 1999)