The Number of Neutrinos and the Left-Right Symmetric Model

Abstract

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

Comments: 11 pages, 3 figures