Weak Neutral Currents Based on Urbaryon-Lepton Correspondence

Abstract

Possibilities of neutral currents are discussed on the basis of the urbaryon-lepton corre· spondence under the usual assumptions of (i) the separate conservation of muon and electron numbers, (ii) muon-electron universality and (iii) the two-component theory of massless neutrinos. According to this correspondence, two types of hadronic neutral currents are obtained. One is U-spin invariant and the other allows the transition between charmed and ordinary hadrons. On the other hand, space-time structures of both hadronic and leptonic neutral current are assumed to be expressed as any combinations of vector and axial-vector. The A/V ratio of neutral currents is calculated by these hadronic neutral currents in the framework of quartet quark parton model from CERN-G. G. M. ne'utral current data. As a result, two solutions, 0.17±0.07 (V dominant) and 5.92±2.19 (A dominant), are derived because of V, A symmetry of total cross sections of neutrino (anti-neutrino) reactions. As for the iso-spin structure of hadronic neutral current, it is generally determined through an analysis of single pion productions whether the contribution of iso-vector current to the cross sections is larger than that of iso·scalar current or not. Moreover, this internal struc­ ture can also be determined by elastic neutrino-electron scattering in our case. The results obtained in this scattering show that either iso-vector or iso-scalar current are mainly contained. Its mixing rate is 20~30%. Other models of hadronic neutral currents are analyzed regarding their iso-spin structure.