Protonium annihilation in P-wave using low-density (ρ/ρ∼10−3) hydrogen targets. Measurements of cascade times and widths

The use of low-density hydrogen targets is demonstrated experimentally to be a new way of selecting protonium (ppBAR atom) annihilations with initial angular momentum L=1. The mean value and the width of the time distributions which occur between protonium formation and annihilation have been measured at room temperature at 8.2, 4.1, 2.1 mbar. They are (110+/-10; 45+/-5), (145+/-15; 82+/-9) and (210+/-25; 125+/-9) ns, respectively.