Neutral-current phenomena within the left-right-symmetric unified theory of quarks and leptons
- 1 January 1978
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review D
- Vol. 17 (1), 131-150
- https://doi.org/10.1103/physrevd.17.131
Abstract
The neutral-current weak-interaction sector of the left-right-symmetric unified theory of quarks and leptons based on the symmetry structure and its subgroup (suggested in earlier papers) is studied in detail here. The theory admits in general of two weak neutral gauge bosons and [and two sets of left and right charged ()]. As pointed out earlier, there are two distinct possibilities for the pattern of spontaneous symmetry breaking which lead to the mass relations (i) , (ii) . Case (i) is identical to the familiar SU(2) × U(1) theory for all predictions. Case (ii), on the other hand, leads to departures from SU(2) × U(1). One of the crucial theorems following from our investigation is that such departures occur only for the electron-induced atomic parity experiments and not for neutrino-induced weak processes in the chiral -invariant limit, in which mixing as well as fermion masses vanish. In this manner (for the chiral limit defined above), SU(2) × U(1) becomes an integral and stable ingredient of the left-right-symmetric theory for both cases (i) and (ii) insofar as their predictions for neutrino-induced reactions are concerned; the differences between the two cases (in this chiral limit) lie solely in their predictions regarding atomic parity violation and, of course, the masses of the two neutral particles and . We study the chiral as well as the nonchiral cases and compare their predictions with experiments, observing that approximate or exact global chiral symmetry of the left-right-symmetric theory is a point of good agreement between theory and all the present neutral-current experiments. We exhibit the dependence of the atomic parity-violation parameter
Keywords
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