High Energy Neutrino Reactions and Physical Interpretation of the Weak Angle by the Theory of Weak Bosons

Abstract

Of the neutrino reactions, the quasi-elastic reactions (I) ))L + n-'7p +l-, VL + p-'7n + rand (II) VL + N-'7 Y + r are studied in the theoryO of weak bosons. We assume that all form factors have the same analytic form and the same effective mass as that of the isovector part of the nucleon electro-magnetic form factor. In comparison with the results of the local (Fermi) interaction theory, the results of the present work on the weak boson theory are in better agreement with recent observations in the following points: A) The total cross sections for the neutrino reactions (I) and (II) become smaller than those of the local interaction theory. B) The ratios of the two reactions (1) and (II), with regard to the total cross sections also become smaller. C) As for the differential cross sections, the weak boson theory leads us to a larger ratio of the forward. to the backward than that predicted by the local interaction theory. We also assume the existence of one or two kinds of weak bosons, Wo (which couples with the .:1S=O baryon currents) and W 1 (which couples with the .:1S=l baryon currents), and suggest an explanation of the physical meaning of the weak angle (j in terms of these bosons. The experiments on the total cross section and the differential cross section for quasi-elastic . neutrino· reactions are in favour of our prediction, which may be considered as strong, although indirect, support for our assumption that weak bosons should exist. The theory of weak interactions which is formulated in terms of the current­ current interaction 2 ) with the universal coupling constant, has received considerable support from the conserved vector current (c. v. c.) hypothesis. 3 ) This hypothesis was originally postulated in analogy to the electromagnetic interaction and was shown to be true by means of the /3-ray spectra 4 ) with the larger energy release. However, difficulties were encountered when it was shown that the coupling constants were not universaP) in various modes of /3-decay (with LiS = 0 and with