Bruno Touschek and AdA: from Frascati to Orsay. In memory of Bruno Touschek, who passed away 40 years ago, on May 25th, 1978

Abstract: The first electron-positron collisions in a laboratory were observed in 1963-1964 at the Laboratoire de l'Acc\'el\'erateur Lin\'eaire d'Orsay, in France, with the storage ring AdA, which had been constructed in the Italian National Laboratories of Frascati in 1960, under the guidance of Bruno Touschek. The making of the collaboration between the two laboratories included visits between Orsay and Frascati, letters between Rome and Paris, and culminated with AdA leaving Frascati on July 4th, 1962 to cross the Alps on a truck, with the doughnut degassed to $10^{-9}$mmHg through pumps powered by sets of heavy batteries. This epoch-making trip and the exchanges which preceded it are described through unpublished documents and interviews with some of its protagonists, Carlo Bernardini, Francois Lacoste, Jacques Ha\"issinski, Maurice L\'evy.