Bounds of the mass of Z' and the neutral mixing angles in general SU(2)_L x SU(2)_R x U(1) models

Abstract

We consider phenomenological constraints on the mass $M_{Z^{\prime }}$ and the two mixing angles ${\theta }_R$ and $\xi$ of the neutral sector in a very general class of $SU(2{)}_L\times SU(2{)}_R\times U(1)$ models using electroweak data. We do not make any specific assumptions such as left-right symmetry or the Higgs structure. The analysis of the neutral sector has the advantage that it has relatively fewer parameters compared to the charged sector since the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements in the right-handed sector do not enter into the analysis, hence the number of various possibilities from a big parameter space is reduced. We utilize theoretical considerations on the masses of the gauge particles and the mixing angles. We combine the precision electroweak data from LEP I and the low-energy neutral-current experimental data to constrain the parameters introduced in the model. It turns out that $M_{Z^{\prime }}>400$ GeV, $-0.0028<\xi <0.0065$ with little constraint on ${\theta }_R$. In the left-right symmetric theory, $M_{Z^{\prime }}$ should be larger than 900 GeV. With these constraints, we compare the values for $\sigma (e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-})$, $\sigma (e^{+}{e}^{-}\to b\bar{b})$ and $A_{FB}^{\ell }$ at LEP II with experimental values.

Comments: 34 pages, a LaTeX file with macros elsart and pictex. 4 Figures