The Heavy Quanta Theory of Nuclear and Cosmic Ray Phenomena

Abstract

In 1935 Yukawa suggested in a paper in the Proceedings of the Physico-Mathematical Society of Japan ¹) that the exchange forces between heavy particles (protons and neutrons) must be attributed to the action of an intervening field and, in particular, may be regarded as a second order effect due to the consecutive emission and absorption of charged “heavy quanta”, just as the electromagnetic interaction between two charged particles can be described by the quantized electromagnetic field. In order to explain the range of about 2 × 10⁻¹³ cm of the nuclear forces, he assumed that this quantum had a mass about 200 times as large as the electron mass: m ≈ 200 m. In his original theory this field was tentatively regarded as a scalar field. Then, however, it turned out ²) that, if the energy of the field of heavy quanta was assumed to be positive, the exchange force between a proton and a neutron became repulsive in a ³S state, in contradiction to the fact that this is the ground state of the deuteron. Since in the mean time experiments on cosmic ray phenomena ³) ⁴) ⁵) ⁶) had suggested the existence of a charged particle just having a mass of the order of magnitude 200 m, which might be identified with the quantum of Yukaw a’s theory ⁷), Yukawa expressed his intention to investigate whether this difficulty with the sign of the proton-neutron force could be removed by introducing a non-scalar heavy quantum field ²).