Neutral-current phenomena within the left-right-symmetric unified theory of quarks and leptons

Citations Over TimeTop 10% of 1978 papers

Abstract

The neutral-current weak-interaction sector of the left-right-symmetric unified theory of quarks and leptons based on the symmetry structure $\mathrm{SU}{(2)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(2)}_{R}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(4)}_{L+R}^{\ensuremath{'}}$ and its subgroup $\mathrm{SU}{(2)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(2)}_{R}\ifmmode\times\else\texttimes\fi{}\mathrm{SU}{(3)}_{L+R}^{\ensuremath{'}}\ifmmode\times\else\texttimes\fi{}\mathrm{U}{(1)}_{L+R}$ (suggested in earlier papers) is studied in detail here. The theory admits in general of two weak neutral gauge bosons ${N}_{1}$ and ${N}_{2}$ [and two sets of left and right charged $W'\mathrm{s}$ (${W}_{L}^{\ifmmode\pm\else\textpm\fi{}},{W}_{R}^{\ifmmode\pm\else\textpm\fi{}}$)]. As pointed out earlier, there are two distinct possibilities for the pattern of spontaneous symmetry breaking which lead to the mass relations (i) $m_{{N}_{1}}^{}{}_{}{}^{2}\ensuremath{\sim}m_{{W}_{L}^{+}}^{}{}_{}{}^{2}\ensuremath{\ll}m_{{N}_{2}}^{}{}_{}{}^{2}$, (ii) $m_{{N}_{1}}^{}{}_{}{}^{2}\ensuremath{\sim}m_{{N}_{2}}^{}{}_{}{}^{2}\ensuremath{\sim}m_{{W}_{L}^{+}}^{}{}_{}{}^{2}$. Case (i) is identical to the familiar SU(2) \ifmmode\times\else\texttimes\fi{} U(1) theory for all predictions. Case (ii), on the other hand, leads to departures from SU(2) \ifmmode\times\else\texttimes\fi{} 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 ${\ensuremath{\gamma}}_{5}$-invariant limit, in which ${W}_{L}\ensuremath{-}{W}_{R}$ mixing as well as fermion masses vanish. In this manner (for the chiral limit defined above), SU(2) \ifmmode\times\else\texttimes\fi{} 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 ${N}_{1}$ and ${N}_{2}$. 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 ${Q}_{W}$ on the masses of the two neutral particles ${N}_{1}$ and ${N}_{2}$ and remark in particular that (depending upon the sign and magnitude of ${Q}_{W}$), there is the exciting experimental possibility within the left-right-symmetric theory that the mass of one of the neutral gauge particles is sensibly smaller than that of the charged ${W}_{L}^{\ifmmode\pm\else\textpm\fi{}}$. This particular possibility does not materialize, if one insists on exact atomic parity conservation.

Related Papers

• → Lepton flavour violating signals of gauge bosonsZ at futuree e colliders(2003)5 cited
• → Tests for neutral heavy leptons in multilepton events(1977)5 cited
• Universal mixing of leptons in a gauge theory of weak interactions(1979)
• → Condensation of light bosons in gauge theories(1984)
• → Remarks on heavy leptons(1986)