Rafael Armenteros (1922-2004)

Rafael Armenteros passed away on Friday, 5 March, to the immense sadness of his family and friends. Having begun his scientific career at the University of Manchester, he took part in the observation of cosmic rays at the Pic du Midi laboratory with Professors Blackett and Butler and participated in the research of the Ecole Polytechnique team led by Professor Leprince-Ringuet consisting of Gregory, Lagarrigue, Muller and Peyrou. He subsequently worked at CERN with Peyrou, who was by then Head of the Track Chamber (TC) Division.
In this early part of his professional career, he was directly involved in the discovery of many elementary particles, including two strange neutral particles (Lambda and K0), and in the observation of the decay of the Xi-minus into a Lambda and a Pi-minus. He then took part in CERN's most famous experiments, the bubble chamber experiments, in which he was one of the leading figures right up to the last one. Following the exceptional scientific results of the 1960s, these experiments cleared the way for another rich harvest of new particles. Rafael was the co-author of numerous internationally renowned contributions in the fields of meson spectroscopy, proton-antiproton annihilation and the understanding of strong interactions. He co-developed the "Armenteros-Podolanski plot" event selection technique, which is still used today in heavy ion physics. Thanks to a trick of the alphabet, Alvarez and Armenteros were the particle physicists of the time whose names were the most frequently cited.

It should be remembered that, in those days, the members of a physics experiment collaboration could be counted on two hands, which allowed them to be personally involved in the experiment from start to finish, from the photographing of events right through to their interpretation. The analysis of experiments was done in small groups. With his enthusiasm and human warmth, Rafael had an exceptional gift for inspiring and guiding young undergraduates and PhD students in their first steps in physics. Sharing their wonderment at each new observation, he always seemed to be inspired by the words of one of his favourite Spanish poets, Antonio Machado: "caminante no hay camino, se hace camino al andar" ("Wanderer, there is no way, you make the way as you go").
Rafael Armenteros carried with him the troubles of his country, the 1936-1939 Civil War and an immense frustration following the triumph of dictatorship. The Spanish Republic funded his higher education in the United Kingdom and he became one of the great Spanish exiles who made important contributions to world culture.
Towards the end of the 1970s, as a new age was dawning for Spain, Rafael made an emotional return to his homeland after a long absence. From that time onwards, he became wholeheartedly involved in shaping the development of particle physics in Spain. He made ever more frequent trips to his homeland and could be proud of the decisive role he played in Spain's return to CERN.
One memory in particular stands out among the many we will retain of him: that of evenings spent in his office for no specific reason other than a feeling of satisfaction that came from having made progress in an analysis. We would talk together, a glass of excellent Rioja in our hands, while Rafael drew deeply on his pipe. An atmosphere of serenity reigned in which everyone, without being really aware of it, experienced a simple sense of well-being engendered by the buzz of friendly conversation.
With the passing-away of Rafael Armenteros, we have lost one of the physicists of CERN's pioneering era and one of the key players in the first discoveries that helped to establish the Laboratory's renown. We have also lost a friend with whom we shared some inspiring, unforgettable hours.

His friends and colleagues