Rethinking antiparticles. Hermann Weyl's contribution to neutrino physics

This paper focuses on Hermann Weyl's two-component theory and frames it within the early development of different theories of spinors and the history of the discovery of parity violation in weak interactions. In order to show the implications of Weyl's theory, the paper discusses the case study of Ettore Majorana's symmetric theory of electron and positron (1937), as well as its role in inspiring Case's formulation of parity violation for massive neutrinos in 1957. In doing so, this paper clarifies the relevance of Weyl's and Majorana's theories for the foundations of neutrino physics and emphasizes which conceptual aspects of Weyl's approach led to Lee's and Yang's works on neutrino physics and to the solution of the theta-tau puzzle in 1957. This contribution thus sheds a light on the alleged “re-discovery” of Weyl's and Majorana's theories in 1957, by showing that this did not happen all of a sudden. On the contrary, the scientific community was well versed in applying these theories in the 1950s on the ground of previous studies that involved important actors in both Europe and United States.