At the LEAP 2013 conference dinner this evening in Uppsala the after dinner speaker was Prof. Gösta Ekspong (91 years old). His talk detailed his recollections of the discovery of the antiproton at the Bevatron in 1955, at which time he was a young postdoc. He had previously done his doctorate on cosmic ray studies with emulsions, and had gone to Berkeley to work with one of the groups which were searching for antiproton annihilations in emulsions. After the initial discovery of a "negatively charged particle with protonic mass" by means of momentum and velocity measurements, focus turned to the search for the annihilation star in the emulsion in order to confirm the discovery of the antiproton. It took 3 weeks to analyse the emulsion plates, so since "he had nothing better to do" he joined the scanning teams looking for the annihilation star. After many weeks and after becoming disheartened after "looking at so many thousand of pion tracks", late one Saturday evening he discovered the first antiproton annihilation star!  

We thought he would be interested to see the movie of the antiproton annihilation taken with the new gel for our AEgIS experiment. So in the attached picture you can see Andreas Knecht showing Prof. Ekspong the annihilation movie on his iPhone! He was very impressed and very interested to learn about the automated emulsion scanning facility at the Albert Einstein Center in Bern (particularly in light of studying so many pions!) and the new application of emulsions to the study of the gravity of antimatter!   

James Storey (13 June 2013)