Bounding the magnetic and electric dipole moments of tau nu from the process e+e- --> nu bar nu gamma in E6 Superstring Models

Abstract

We obtain bounds on the anomalous magnetic and electric dipole moments of the tau-neutrino through the reaction $e^{+}{e}^{-}\to \nu \bar{\nu }\gamma$ at the $Z_1$-pole in the framework of a Left-Right symmetric model and a class of $E_6$ inspired models with an additional neutral vector boson $Z_{\theta }$. We use the data collected by the L3 Collaboration at LEP. For the parameters of the $E_6$ model we consider the mixing angle ${\theta }_{E_6}=37.8^o$ and $M_{Z_{\theta }}=7M_{Z_1}$. We find that our bounds are of the same order of magnitude as those obtained in other extensions of the Standard Model.

Comments: 17 pages, 2 figure