New limits on neutrino magnetic moment through non-vanishing 13-mixing

Abstract

The relatively large value of neutrino mixing angle \theta_{13} set by recent measurements allows us to use solar neutrinos to set a limit on neutrino magnetic moment involving second and third families, \mu_{\mu\tau}. The existence of a random magnetic field in solar convective zone can produce a significant anti-neutrino flux when a non-vanishing neutrino magnetic moment is assumed. Even if we consider a vanishing neutrino magnetic moment involving the first family, electron anti-neutrinos are indirectly produced through the mixing between first and third families and non-vanishing \mu_{\mu\tau}. Using KamLAND limits on the solar flux of electron anti-neutrino, we set the limit \mu_{\mu\tau} < 0.5e-11 Bohr magneton for a reasonable assumption on the behavior of solar magnetic fields. This is the first time a limit on \mu_{\mu\tau} is established in the literature directly from neutrino interaction with magnetic fields, and, interestingly enough, is comparable with the limits on neutrino magnetic moment involving the first family and with the ones coming from modifications on electroweak cross section.