2004/12/21 by Graciela B. Gelmini · 1 citation
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Neutrino #Neutrino Physics Research #Particle physics #Particle physics theoretical and experimental studies #Physics #hep-ph
paper · pdf · doi:10.1088/0031-8949/2005/t121/019
published as Phys.Scripta T121 (2005) 131-136 · Talk given at the Nobel Symposium on Neutrino Physics, Enkoping, Sweden, Augus 19-24, 2004; 16 pages
arxiv created 2004/12/21 · openalex publication_date 2005/01/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Neutrinos from the Big Bang are theoretically expected to be the most abundant particles in the Universe after the photons of the Cosmic Microwave Background (CMB). Unlike the relic photons, relic neutrinos have not so far been observed. The Cosmic Neutrino Background (CνB) is the oldest relic from the Big Bang, produced a few seconds after the Bang itself. Due to their impact in cosmology, relic neutrinos may be revealed indirectly in the near future through cosmological observations. In this talk we concentrate on other proposals, made in the last 30 years, to try to detect the CνB directly, either in laboratory searches (through tiny accelerations they produce on macroscopic targets) or through astrophysical observations (looking for absorption dips in the flux of Ultra-High Energy (UHE) neutrinos, due to the annihilation of these neutrinos with relic neutrinos at the Z-resonance). We concentrate mainly on the first possibility. We show that, given present bounds on neutrino masses, lepton number in the Universe and gravitational clustering of neutrinos, all expected laboratory effects of relic neutrinos are far from observability, awaiting future technological advances to reach the necessary sensitivity. The problem for astrophysical searches is that sources of UHE neutrinos at the extreme energies required may not exist. If they do exist, we could reveal the existence, and possibly the mass spectrum, of relic neutrinos, with detectors of UHE neutrinos (such as ANITA, Auger, EUSO, OWL, RICE and SalSA).