Investigation of neutrino properties in the process e+e---> nu nu -bar gamma.

Abstract

Assuming a nonvanishing neutrino magnetic moment $\ensuremath{\mu}$ we study $\ensuremath{\tau}$-neutrino properties in the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\nu}\overline{\ensuremath{\nu}}\ensuremath{\gamma}$ from the single photon searches at colliders. We find that for a sufficiently large value of neutrino mass, i.e., $m>2.1\ifmmode\times\else\texttimes\fi{}(\frac{{10}^{10}\ensuremath{\mu}}{{\ensuremath{\mu}}_{B}})$ MeV (where ${\ensuremath{\mu}}_{B}=\frac{e}{2{m}_{e}}$ is the Bohr magneton), the interference between the diagrams with ${Z}^{0}$ and $\ensuremath{\gamma}$ exchange becomes important and should be taken into account in future ${e}^{+}{e}^{\ensuremath{-}}$ experiments. Some cosmological and astrophysical implications of this new heavy-neutrino scenario are briefly discussed.