title: New constraints on neutrino physics from BOOMERANG data
abstract: We have performed a likelihood analysis of the recent data on the cosmic microwave background radiation anisotropy from the BOOMERANG experiment. These data place a strong upper bound on the radiation density present at recombination. Expressed in terms of the equivalent number of neutrino species the 2sigma bound is N(nu)</=13. This bound is not flavor sensitive. It also applies to the Universe at a much later epoch, and as such places severe limits on scenarios with decaying neutrinos. The bound also yields a firm upper limit on the lepton asymmetry in the Universe.
authors.affiliation: NORDITA, Blegdamsvej 17, DK-2100 Copenhagen, Denmark.
authors.initials: S
authors.lastname: Hannestad