Fifty years of Yang–Mills Theories: a phenomenological point of view

On the occasion of the celebration of the first half-century of Yang–Mills theories, I am contributing a personal recollection of how the subject, in its early times, confronted physical reality, that is, its “phenomenology”. There is nothing original in this work, except, perhaps, my own points of view. But I hope that the older practitioners of the field will find here grounds for nostalgia, or good reasons to disagree with me. Younger addicts may learn that history does not resemble at all what is reflected in current textbooks: it was orders of magnitude more fascinating. This account is dedicated to the memory of my thesis advisor: Angel Morales.