Leptonin

Leptonin is a hypothetical particle proposed in the 1930s as a possible mediator of the weak nuclear force, which is responsible for certain types of radioactive decay. The concept was introduced by Hideki Yukawa, who also proposed the pion as a mediator of the strong nuclear force. Leptonin was intended to explain the phenomenon of beta decay, where a neutron in an atomic nucleus decays into a proton, an electron, and an antineutrino.

The existence of leptonin was not confirmed experimentally, and the particle was eventually replaced by the concept of the W and Z bosons, which were discovered in the 1980s at CERN. These bosons are indeed responsible for the weak nuclear force and are part of the Standard Model of particle physics. The leptonin hypothesis is now considered obsolete, but it played a significant role in the development of modern particle physics.