Introductory remarks about new particles

Abstract

On 11 November 1974, elementary particle physics entered a new era, with simultaneous announcements from the east and west coasts of America that a new heavy particle with astonishingly small decay width had been observed in two quite independent experiments, of different types. Since that time we have all been living through one of the most exciting periods which our field of research has known. The possibility that there might exist new particles of some kind, and possibly of more than one kind, was very much ‘in the air’ during the preceding year or so (Iliopoulos 1974). Attractive theoretical ideas had been put forward some years before (Weinberg 1967) suggesting that a finite gauge theory could be constructed for the weak interactions, which could achieve a unification of the weak and electromagnetic interactions, a goal long sought (Salam & Ward 1964). When a proof of this finiteness (renormalizability) was achieved by t’Hooft (1971 a , b ), physicists had for the first time calculable and meaningful theories unifying the weak and electromagnetic interactions, the analogue for the weak interactions to the photon for the electromagnetic field being very heavy vector bosons, both charged and neutral, whose direct detection still lies quite far in the future. However, not all such theories were necessarily finite. Further conditions had to be met, and a key feature of these is the situation concerning the neutral weak currents.