How Magnetic is the Dirac Neutrino?
  We derive model-independent, "naturalness" upper bounds on the magnetic moments \mu_\nu of Dirac neutrinos generated by physics above the scale of electroweak symmetry breaking. In the absence of fine-tuning of effective operator coefficients, we find that current information on neutrino mass implies that |\mu_\nu | < 10^(-14) Bohr magnetons. This bound is several orders of magnitude stronger than those obtained from analyses of solar and reactor neutrino data and astrophysical observations. 
Nicole F. Bell, Vincenzo Cirigliano, Michael J. Ramsey-Musolf, Petr   Vogel, Mark B. Wise