Neutrino masses

Abstract

Abstract.Even if neutrino masses are unknown, we know neutrinos are much lighter than the other fermions we know, and we do not have a good explanation for it. In the Standard Model of elementary particles neutrinos are exactly massless, although this is not insured by any basic principle. Non-zero neutrino masses arise in many extensions of the Standard Model. Massive neutrinos and their associated properties, such as the Dirac or Majorana character of neutrinos, their mixings, lifetimes and magnetic or electric moments, may have very important consequences in astrophysics, cosmology and particle physics. Here we explore these consequences and the constraints they already impose on neutrino properties, as well as the large body of experimental and observational efforts currently devoted to elucidate the mystery of neutrino masses.Several hints for non-zero masses in solar and atmospheric neutrinos, that will be confirmed or rejected in the near future, make this field of research particularly exciting at present.

Emergent dark matter, baryon, and lepton numbers

“…This section is dedicated to the overview of how distributions of particles with mass mixing evolve over time. A good review of this material can be found in [20]. We first present fermion mixing and then discuss scalars.…”

Neutrino mass problem: the state of the art

“…Among the reviews close to the topics of the various sections in this paper we point out those by Zatsepin and Smirnov [5] and Muto and Klapdor [6] (the general properties of neutrinos), Gelmini and Roulet [7] and Boehm and Vogel [8] (neutrino masses), Wojcicki [9] (neutrino oscillations and the masses of n m and n t ), Moe and Vogel [10,11] and Shchepkin [12] (double beta decay), Borovo|¯and Khakimov [13] (experiments with reactor neutrinos), Weinheimer et al [14] and Belesev et al [15] (the mass of n e ), and Imshennik and Nadezhin [16] (Supernova 1987A). The values of some quantities are those accepted as of April 1997.…”

“…Then this assumption leads to such important consequences (neutrino instability, a nonzero magnetic moment, oscillations, and the possibility of solving some important astrophysical problems{) that it is worthwhile stepping outside the Standard Model, the more so that the experiments verifying the theoretical results are not absolutely correct but only within a certain error and there occurs no first physical principle that requires the neutrino to be massless. The question of generalizing the Standard Model was examined by Gelmini and Roulet [7] and Boehm and Vogel [8]. Here we attempt to do this in the most pictorial way possible.…”

Double beta decay—Physics beyond the standard model now, and in future (GENIUS)

“…21. The original figure is taken from [Gel95]. While the GE-NIUS 1 ton sensitivity is sufficient (even in the worst case of m νe << m νµ ) to extend to smaller values of ∆m 2 at large mixing angles, GENIUS 10 GENIUS 10 t GENIUS 1 t Fig.…”

“…Fig. 22 (background from [Gel95]) compares the double beta worst case of strong hierarchy (m 1 /m 2 = 0), to the KAMIOKANDE allowed range for atmospheric neutrino oscillations. GENIUS 1 ton would already be able to test the ν e ↔ ν µ oscillation hypothesis.…”