A New Vectorlike Model of the Weak Interactions

Abstract

A vectorlike model of the weak interactions with six quark flavors is proposed. The model is based on the gauge theory with the group SU (2) XU (1). It is shown that the model well describes the rise of the ratio of li- to v-induced total cross sections by the charged current. Discussions on the various weak phenomena including the parity violation in atomic physics are given. Gauge theory is interesting as a candidate for the so-called unified theory m particle physics. 1l In the framework of the gauge theory, many kinds of models can be considered. Hovvever, any meaningful model must be free from the triangle anomalies which destroy the renormalizability.'l The anomalies are most naturally removed in the vector like model. 1l Furthermore, the vectorlike model has very interesting properties. For example, we might be able to understand, in the frame­ work of the vectorlike gauge theory, that the left-right asymmetry of nature 1s caused by the spontaneous symmetry breaking. Recently several authors have proposed the models of this kind. 3l One of the characteristic features of their models is that the hadronic neutral current is purely vector type. Therefore their models predict, for instance, O'Nc/ ONc = 1, where Oxc(O'Nc) stands for the inclusive neutrino (antineutrino) cross section by the neu­ tral current. However, experimental data show an apparent departure from their predictions. The most recent data indicate if~c/ O~c<0.61 ± 0.25, where D denotes the averaged nucleon target.') The vectorlike models with the parity violating neutral current have been already proposed.sl,Bl In the model of the Kanazawa group, quark flavors transform as triplets under the weak SU (2), and an artificial angle relation has been assumed in order to guarantee the universality of the charged current. sl The Barnett's model 1 6) is very beautiful and well describes the anomaly in ifcc at high energies with bottom-quark mass ~5 Ge V, where ifcc is the antineutrino-nucleon inclusive cross section by the charged current.7l,lll His model predicts opposite sign for the parity violation in atomic physics compared with the prediction of the conventional GIM modeP0l for Bi atom, if the transformation properties of the lepton sector are reasonably chosen.8l