SU(2)L ⊗ SU(2)R ⊗ U(1) gauge models confronting neutral current data

Abstract

We study the neutral current (NC) sector of the general SU(2) L ⊗ SU(2) R ⊗ U(1) gauge model of weak and electromagnetic interactions with L-R symmetric couplings g L = g R , and with conventional fermion multiplet assignments. We make a least-squares fit of fourteen experimental quantities in the full parameter space, as well as in several sub-spaces defining specific models. We discuss all previously studied SU(2) L ⊗ SU(2) R ⊗ U(1) models, the Weinberg-Salam model, an SU(2) ⊗ U(1) vector model, with and without parity violation in atoms. We give 90% confidence ranges of all the parameters, NC coupling constants, and the muon forward-backward asymmetry in unpolarized colliding e + e − beams. Among the coupling constants the same two linear relations must hold as given in SU(2) ⊗ U(1), and in addition the new relations β = −2g A , δ = 0, α − β + 3( γ − δ ) = 0, α − 3 γ − 4(h AA + g A ) = 0, β = −4h VA , δ = 0 .