Why Are Neutrinos Light? -- An Alternative
We review the recent proposal that neutrinos are light because their masses are proportional to a low scale, f, of lepton flavor symmetry breaking. This mechanism is testable because the resulting pseudo-Goldstone bosons, of mass m_G, couple strongly with the neutrinos, affecting the acoustic oscillations during the eV era of the early universe that generate the peaks in the CMB radiation. Characteristic signals result over a very wide range of (f, m_G) because of a change in the total relativistic energy density and because the neutrinos scatter rather than free-stream. Thermodynamics allows a precise calculation of the signal, so that observations would not only confirm the late-time neutrino mass mechanism, but could also determine whether the neutrino spectrum is degenerate, inverted or hierarchical and whether the neutrinos are Dirac or Majorana. The flavor symmetries could also give light sterile states. If the masses of the sterile neutrinos turn on after the MeV era, the LSND oscillations can be explained without upsetting big bang nucleosynthesis, and, since the sterile states decay to lighter neutrinos and pseudo-Goldstones, without giving too much hot dark matter.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- Physics Division
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 964270
- Report Number(s):
- LBNL-56209; TRN: US0903667
- Resource Relation:
- Conference: Fujihara Seminar on Neutrino Mass and Seesaw Mechanism, Tsukuba, Ibaraki, Japan, 23-25 Feb 2004
- Country of Publication:
- United States
- Language:
- English
Similar Records
Impact of neutrino flavor oscillations on the neutrino-driven wind nucleosynthesis of an electron-capture supernova
Resolution of puzzles from the LSND, KARMEN, and MiniBooNE experiments