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Title: Are there sterile neutrinos?

Abstract

We update the hints of the existence of sterile neutrinos.

Authors:
 [1]
  1. Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)
Publication Date:
OSTI Identifier:
22306111
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1604; Journal Issue: 1; Conference: PPC 2013: 7. international conference on interconnections between particle physics and cosmology, Lead-Deadwood, SD (United States), 24 Jun - 6 Jul 2013; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; INTERACTIONS; NEUTRINO OSCILLATION; NEUTRINOS

Citation Formats

Kayser, Boris. Are there sterile neutrinos?. United States: N. p., 2014. Web. doi:10.1063/1.4883431.
Kayser, Boris. Are there sterile neutrinos?. United States. doi:10.1063/1.4883431.
Kayser, Boris. Tue . "Are there sterile neutrinos?". United States. doi:10.1063/1.4883431.
@article{osti_22306111,
title = {Are there sterile neutrinos?},
author = {Kayser, Boris},
abstractNote = {We update the hints of the existence of sterile neutrinos.},
doi = {10.1063/1.4883431},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1604,
place = {United States},
year = {Tue Jun 24 00:00:00 EDT 2014},
month = {Tue Jun 24 00:00:00 EDT 2014}
}
  • Here, we report results of a search for oscillations involving a light sterile neutrino over distances of 1.04 and 735 km in a ν μ-dominated beam with a peak energy of 3 GeV. The data, from an exposure of 10.56 × 10 20 protons on target, are analyzed using a phenomenological model with one sterile neutrino. We constrain the mixing parameters θ 24 and Δm 41 2 and set limits on parameters of the four-dimensional Pontecorvo-Maki-Nakagawa-Sakata matrix, |U μ4| 2 and |U τ4| 2, under the assumption that mixing between νe and νs is negligible (|U e4| 2=0). No evidence for νmore » μ → ν s transitions is found and we set a world-leading limit on θ 24 for values of Δm 41 2 ≲ 1 eV 2.« less
  • Here, we report results of a search for oscillations involving a light sterile neutrino over distances of 1.04 and 735 km in a ν μ-dominated beam with a peak energy of 3 GeV. Furthermore, the data, from an exposure of 10.56 × 10 20 protons on target, are analyzed using a phenomenological model with one sterile neutrino. We constrain the mixing parameters θ 24 and Δ mmore » $$2\atop{41}$$ and set limits on parameters of the four-dimensional Pontecorvo-Maki-Nakagawa-Sakata matrix, |U μ4| 2 and |U τ 4| 2, under the assumption that mixing between ν e and ν s is negligible (|U e 4| 2 = 0). No evidence for ν μ → ν s transitions is found and we set a world-leading limit on θ 24 for values of Δm$$2\atop{41}$$ ≲ 1 eV 2.« less
  • We reexamine the big bang nucleosynthesis (BBN) bounds on the mixing of neutrinos with sterile species. These bounds depend on the assumption that the relic neutrino asymmetry {ital L}{sub {nu}} is very small. We show that for {ital L}{sub {nu}} large enough (greater than about 10{sup {endash}5}) the standard BBN bounds do not apply. We apply this result to the sterile neutrino solution to the atmospheric neutrino anomaly and show that for {ital L}{sub {nu}}{approx_gt}7{times}10{sup {minus}5} it is consistent with BBN. The BBN bounds on sterile neutrinos mixing with electron neutrinos can also be weakened considerably. {copyright} {ital 1995 Themore » American Physical Society.}« less
  • By combining data from cosmic microwave background (CMB) experiments (including the recent BOOMERANG-2K2 results), large scale structure (LSS) and Lyman-{alpha} forest observations, we constrain the hypothesis of a fourth, sterile, massive neutrino. For the 3 massless + 1 massive neutrino case we bound the mass of the sterile neutrino to m{sub s} < 0.55eV at 95% c.l.. These results exclude at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly. We then generalize the analysis to account for active neutrino masses (which tightens the limit to m{sub s} < 0.51eV) and the possibility that the sterilemore » abundance is not thermal. In the latter case, the constraints in the (mass, density) plane are non-trivial. For a mass of > 1eV or < 0.05eV the cosmological energy density in sterile neutrinos is always constrained to be {omega}{sub {nu}} < 0.005 at 95% c.l.. However, for a sterile neutrino mass of {approx} 0.25 eV, {omega}{sub {nu}} can be as large as 0.015.« less