Bounds on the Number of Light Neutrinos Species, g'1 Coupling and Z − Z' Mixing Angle in a U(1)B−L Model

Abstract

The constraints on the number of neutrinos generations, g'1 coupling and Z − Z′ mixing angle through the invisible width method, and in the framework of a U(1)B−L model are obtained. Based on the experimental value reported by the LEP for the rate LEP R = Γinv/ Γ = 5.942 ± 0.016 , we obtained a bound on the g′1 coupling, g′1 ≤ 0.65 . In addition, we derive 90% C.L. bounds on the Z − Z′ mixing angle -2.2 x10^−4 ≤ θ_B-L ≤1.0 ×10^-4, improving the existing bounds by one order of magnitude.