1992/12/08 by Sidney A. Bludman, Bludman, Sidney A.
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #hep-ph
paper · pdf · doi:10.48550/arxiv.hep-ph/9212240
4 pages, Latex
arxiv created 1992/12/08 · arxiv updated 2009/11/30
The best upper bounds on the masses of stable and unstable light neutrinos derive from the upper bound on the total mass density, as inferred from the lower limit t0> 13 Gyr on the dynamical age of the Universe: If the Universe is matter-dominated, mν<35(23)× max [1, (t0/τν)1/2] eV, according as a cosmological constant is (is not) allowed. The best constraints on the radiative decay of light neutrinos derive from the failure to observe prompt gamma rays accompanying the neutrinos from Supernova 1987A: For any mν > 630 eV, this provides a stronger bound on the neutrino transition moment than that obtained from red giants or white dwarfs. For mν> 250 eV or τν< trec∼ 7× 1012 sec, the upper limit on the radiative branching ratio is even smaller than that obtained from the limits on μ-distortion of the cosmic background radiation. Our results improve on earlier cosmological and radiative decay constraints by an overall factor twenty, and allow neutrinos more massive than 35 eV, only if they decay overwhelmingly into singlet majorons or other new particles.