X-rays from Protonium — PS174 Progress Report

Abstract

The purpose of this experiment is to measure the strong interaction shift and width of the atomic 1S groundstate of antiprotonic-hydrogen by observing its K series X-rays. This gives directly the $\bar p$ complex scattering length. Also from a measurement of the L X-rays we can determine the 2P annihilation width and investigate the atomic cascade. $\bar P$-helium runs provide us with a means of optimizing and periodically checking the working of our equipment in addition to their physics interest (strong $\bar p$-He interaction and atomic cascade). To date we have stopped antiprotons in gaseous hydrogen (30K and 300K), deuterium (30K) and helium (30K, 100K and 300K).