Constraints on neutrino-photon interactions from rare Z decays

It is shown that the rare decays Z --> nu(nu) over bar gamma and Z --> nu(nu) over bar gamma gamma are useful to put model-independent bounds on neutrino-one-hoton and neutrino-two-photon interactions. The results are then used to constrain the tau neutrino magnetic moment mu(nutau) and the double radiative decay nu(j) --> nu(i)gammagamma. It is found that the decay Z --> nu(nu) over bar gamma gives a more stringent bound on mu(nutau) than that obtained from Z --> nu(nu) over bar gamma gamma; the latter decay in turn gives limits on the neutrino-two-photon interaction that are less stringent than those obtained for a sterile neutrino nu(s) from the analysis of nu(mu) N --> nu(s)N conversion. (C) 2002 Elsevier Science B.V. All rights reserved.