The number of neutrinos and the left-right symmetric model

Abstract

The meaning of N _v in the Left-Right Symmetric Model (LRSM) is discussed. In its original definition N _v is the number of neutrinos or generations of leptons, so, in the Standard Model its value is three. However the determination of N _v in experiments and in astrophysical observations is subject to different theoretical interpretations. We present arguments that gives N _v as a parameter of the LRSM. Using an experimental value for the rate Γ_inv/Γ_ll̅ we calculate the bound $2.90leq N_{v_{LR}}leq 3.04 (90% {⤪ C.L.})$, where $N_{v_{LR}}$ is a function of the left-right mixing angle ϕ. This range is less restrictive than the one of the standard model.